2576 - distinguish allocated addresses from others

This is the one major refinement on the C programming model I'm planning
to introduce in mu. Instead of Rust's menagerie of pointer types and
static checking, I want to introduce just one new type, and use it to
perform ref-counting at runtime.

So far all we're doing is updating new's interface. The actual
ref-counting implementation is next.

One implication: I might sometimes need duplicate implementations for a
recipe with allocated vs vanilla addresses of the same type. So far it
seems I can get away with just always passing in allocated addresses;
the situations when you want to pass an unallocated address to a recipe
should be few and far between.

11 files changed, 1257 insertions, 1257 deletions

diff --git a/edit/001-editor.mu b/edit/001-editor.mu
index fd44d493..773b7d77 100644
--- a/edit/001-editor.mu
+++ b/edit/001-editor.mu
@@ -2,7 +2,7 @@
 
 # temporary main for this layer: just render the given text at the given
 # screen dimensions, then stop
-recipe! main text:address:array:character [
+recipe! main text:address:shared:array:character [
   local-scope
   load-ingredients
   open-console
@@ -16,8 +16,8 @@ recipe! main text:address:array:character [
 scenario editor-initially-prints-text-to-screen [
   assume-screen 10/width, 5/height
   run [
-    1:address:array:character <- new [abc]
-    new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+    1:address:shared:array:character <- new [abc]
+    new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   ]
   screen-should-contain [
     # top line of screen reserved for menu
@@ -29,11 +29,11 @@ scenario editor-initially-prints-text-to-screen [
 
 container editor-data [
   # editable text: doubly linked list of characters (head contains a special sentinel)
-  data:address:duplex-list:character
-  top-of-screen:address:duplex-list:character
-  bottom-of-screen:address:duplex-list:character
+  data:address:shared:duplex-list:character
+  top-of-screen:address:shared:duplex-list:character
+  bottom-of-screen:address:shared:duplex-list:character
   # location before cursor inside data
-  before-cursor:address:duplex-list:character
+  before-cursor:address:shared:duplex-list:character
 
   # raw bounds of display area on screen
   # always displays from row 1 (leaving row 0 for a menu) and at most until bottom of screen
@@ -47,7 +47,7 @@ container editor-data [
 # creates a new editor widget and renders its initial appearance to screen
 #   top/left/right constrain the screen area available to the new editor
 #   right is exclusive
-recipe new-editor s:address:array:character, screen:address:screen, left:number, right:number -> result:address:editor-data, screen:address:screen [
+recipe new-editor s:address:shared:array:character, screen:address:shared:screen, left:number, right:number -> result:address:shared:editor-data, screen:address:shared:screen [
   local-scope
   load-ingredients
   # no clipping of bounds
@@ -63,11 +63,11 @@ recipe new-editor s:address:array:character, screen:address:screen, left:number,
   *x <- copy 1/top
   x <- get-address *result, cursor-column:offset
   *x <- copy left
-  init:address:address:duplex-list:character <- get-address *result, data:offset
+  init:address:address:shared:duplex-list:character <- get-address *result, data:offset
   *init <- push 167/§, 0/tail
-  top-of-screen:address:address:duplex-list:character <- get-address *result, top-of-screen:offset
+  top-of-screen:address:address:shared:duplex-list:character <- get-address *result, top-of-screen:offset
   *top-of-screen <- copy *init
-  y:address:address:duplex-list:character <- get-address *result, before-cursor:offset
+  y:address:address:shared:duplex-list:character <- get-address *result, before-cursor:offset
   *y <- copy *init
   result <- insert-text result, s
   # initialize cursor to top of screen
@@ -78,7 +78,7 @@ recipe new-editor s:address:array:character, screen:address:screen, left:number,
   <editor-initialization>
 ]
 
-recipe insert-text editor:address:editor-data, text:address:array:character -> editor:address:editor-data [
+recipe insert-text editor:address:shared:editor-data, text:address:shared:array:character -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
   # early exit if text is empty
@@ -87,7 +87,7 @@ recipe insert-text editor:address:editor-data, text:address:array:character -> e
   reply-unless len, editor/same-as-ingredient:0
   idx:number <- copy 0
   # now we can start appending the rest, character by character
-  curr:address:duplex-list:character <- get *editor, data:offset
+  curr:address:shared:duplex-list:character <- get *editor, data:offset
   {
     done?:boolean <- greater-or-equal idx, len
     break-if done?
@@ -104,8 +104,8 @@ recipe insert-text editor:address:editor-data, text:address:array:character -> e
 scenario editor-initializes-without-data [
   assume-screen 5/width, 3/height
   run [
-    1:address:editor-data <- new-editor 0/data, screen:address:screen, 2/left, 5/right
-    2:editor-data <- copy *1:address:editor-data
+    1:address:shared:editor-data <- new-editor 0/data, screen:address:shared:screen, 2/left, 5/right
+    2:editor-data <- copy *1:address:shared:editor-data
   ]
   memory-should-contain [
     # 2 (data) <- just the § sentinel
@@ -127,7 +127,7 @@ scenario editor-initializes-without-data [
 # Assumes cursor should be at coordinates (cursor-row, cursor-column) and
 # updates before-cursor to match. Might also move coordinates if they're
 # outside text.
-recipe render screen:address:screen, editor:address:editor-data -> last-row:number, last-column:number, screen:address:screen, editor:address:editor-data [
+recipe render screen:address:shared:screen, editor:address:shared:editor-data -> last-row:number, last-column:number, screen:address:shared:screen, editor:address:shared:editor-data [
   local-scope
   load-ingredients
   reply-unless editor, 1/top, 0/left, screen/same-as-ingredient:0, editor/same-as-ingredient:1
@@ -135,8 +135,8 @@ recipe render screen:address:screen, editor:address:editor-data -> last-row:numb
   screen-height:number <- screen-height screen
   right:number <- get *editor, right:offset
   # traversing editor
-  curr:address:duplex-list:character <- get *editor, top-of-screen:offset
-  prev:address:duplex-list:character <- copy curr  # just in case curr becomes null and we can't compute prev
+  curr:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+  prev:address:shared:duplex-list:character <- copy curr  # just in case curr becomes null and we can't compute prev
   curr <- next curr
   # traversing screen
   +render-loop-initialization
@@ -145,7 +145,7 @@ recipe render screen:address:screen, editor:address:editor-data -> last-row:numb
   column:number <- copy left
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   screen <- move-cursor screen, row, column
   {
     +next-character
@@ -208,7 +208,7 @@ recipe render screen:address:screen, editor:address:editor-data -> last-row:numb
     loop
   }
   # save first character off-screen
-  bottom-of-screen:address:address:duplex-list:character <- get-address *editor, bottom-of-screen:offset
+  bottom-of-screen:address:address:shared:duplex-list:character <- get-address *editor, bottom-of-screen:offset
   *bottom-of-screen <- copy curr
   # is cursor to the right of the last line? move to end
   {
@@ -225,7 +225,7 @@ recipe render screen:address:screen, editor:address:editor-data -> last-row:numb
   reply row, column, screen/same-as-ingredient:0, editor/same-as-ingredient:1
 ]
 
-recipe clear-line-delimited screen:address:screen, column:number, right:number -> screen:address:screen [
+recipe clear-line-delimited screen:address:shared:screen, column:number, right:number -> screen:address:shared:screen [
   local-scope
   load-ingredients
   space:character <- copy 32/space
@@ -238,7 +238,7 @@ recipe clear-line-delimited screen:address:screen, column:number, right:number -
   }
 ]
 
-recipe clear-screen-from screen:address:screen, row:number, column:number, left:number, right:number -> screen:address:screen [
+recipe clear-screen-from screen:address:shared:screen, row:number, column:number, left:number, right:number -> screen:address:shared:screen [
   local-scope
   load-ingredients
   # if it's the real screen, use the optimized primitive
@@ -254,7 +254,7 @@ recipe clear-screen-from screen:address:screen, row:number, column:number, left:
   reply screen/same-as-ingredient:0
 ]
 
-recipe clear-rest-of-screen screen:address:screen, row:number, left:number, right:number -> screen:address:screen [
+recipe clear-rest-of-screen screen:address:shared:screen, row:number, left:number, right:number -> screen:address:shared:screen [
   local-scope
   load-ingredients
   row <- add row, 1
@@ -273,9 +273,9 @@ recipe clear-rest-of-screen screen:address:screen, row:number, left:number, righ
 scenario editor-initially-prints-multiple-lines [
   assume-screen 5/width, 5/height
   run [
-    s:address:array:character <- new [abc
+    s:address:shared:array:character <- new [abc
 def]
-    new-editor s:address:array:character, screen:address:screen, 0/left, 5/right
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   ]
   screen-should-contain [
     .     .
@@ -288,8 +288,8 @@ def]
 scenario editor-initially-handles-offsets [
   assume-screen 5/width, 5/height
   run [
-    s:address:array:character <- new [abc]
-    new-editor s:address:array:character, screen:address:screen, 1/left, 5/right
+    s:address:shared:array:character <- new [abc]
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 1/left, 5/right
   ]
   screen-should-contain [
     .     .
@@ -301,9 +301,9 @@ scenario editor-initially-handles-offsets [
 scenario editor-initially-prints-multiple-lines-at-offset [
   assume-screen 5/width, 5/height
   run [
-    s:address:array:character <- new [abc
+    s:address:shared:array:character <- new [abc
 def]
-    new-editor s:address:array:character, screen:address:screen, 1/left, 5/right
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 1/left, 5/right
   ]
   screen-should-contain [
     .     .
@@ -316,8 +316,8 @@ def]
 scenario editor-initially-wraps-long-lines [
   assume-screen 5/width, 5/height
   run [
-    s:address:array:character <- new [abc def]
-    new-editor s:address:array:character, screen:address:screen, 0/left, 5/right
+    s:address:shared:array:character <- new [abc def]
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   ]
   screen-should-contain [
     .     .
@@ -336,8 +336,8 @@ scenario editor-initially-wraps-long-lines [
 scenario editor-initially-wraps-barely-long-lines [
   assume-screen 5/width, 5/height
   run [
-    s:address:array:character <- new [abcde]
-    new-editor s:address:array:character, screen:address:screen, 0/left, 5/right
+    s:address:shared:array:character <- new [abcde]
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   ]
   # still wrap, even though the line would fit. We need room to click on the
   # end of the line
@@ -358,10 +358,10 @@ scenario editor-initially-wraps-barely-long-lines [
 scenario editor-initializes-empty-text [
   assume-screen 5/width, 5/height
   run [
-    1:address:array:character <- new []
-    2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    1:address:shared:array:character <- new []
+    2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .     .
@@ -379,10 +379,10 @@ scenario editor-initializes-empty-text [
 scenario render-colors-comments [
   assume-screen 5/width, 5/height
   run [
-    s:address:array:character <- new [abc
+    s:address:shared:array:character <- new [abc
 # de
 f]
-    new-editor s:address:array:character, screen:address:screen, 0/left, 5/right
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   ]
   screen-should-contain [
     .     .
@@ -460,10 +460,10 @@ recipe get-color color:number, c:character -> color:number [
 scenario render-colors-assignment [
   assume-screen 8/width, 5/height
   run [
-    s:address:array:character <- new [abc
+    s:address:shared:array:character <- new [abc
 d <- e
 f]
-    new-editor s:address:array:character, screen:address:screen, 0/left, 8/right
+    new-editor s:address:shared:array:character, screen:address:shared:screen, 0/left, 8/right
   ]
   screen-should-contain [
     .        .
diff --git a/edit/002-typing.mu b/edit/002-typing.mu
index 037c222b..f3f6b321 100644
--- a/edit/002-typing.mu
+++ b/edit/002-typing.mu
@@ -2,16 +2,16 @@
 
 # temporary main: interactive editor
 # hit ctrl-c to exit
-recipe! main text:address:array:character [
+recipe! main text:address:shared:array:character [
   local-scope
   load-ingredients
   open-console
-  editor:address:editor-data <- new-editor text, 0/screen, 5/left, 45/right
+  editor:address:shared:editor-data <- new-editor text, 0/screen, 5/left, 45/right
   editor-event-loop 0/screen, 0/console, editor
   close-console
 ]
 
-recipe editor-event-loop screen:address:screen, console:address:console, editor:address:editor-data -> screen:address:screen, console:address:console, editor:address:editor-data [
+recipe editor-event-loop screen:address:shared:screen, console:address:shared:console, editor:address:shared:editor-data -> screen:address:shared:screen, console:address:shared:console, editor:address:shared:editor-data [
   local-scope
   load-ingredients
   {
@@ -20,7 +20,7 @@ recipe editor-event-loop screen:address:screen, console:address:console, editor:
     cursor-row:number <- get *editor, cursor-row:offset
     cursor-column:number <- get *editor, cursor-column:offset
     screen <- move-cursor screen, cursor-row, cursor-column
-    e:event, console:address:console, found?:boolean, quit?:boolean <- read-event console
+    e:event, console:address:shared:console, found?:boolean, quit?:boolean <- read-event console
     loop-unless found?
     break-if quit?  # only in tests
     trace 10, [app], [next-event]
@@ -45,7 +45,7 @@ recipe editor-event-loop screen:address:screen, console:address:console, editor:
 ]
 
 # process click, return if it was on current editor
-recipe move-cursor-in-editor screen:address:screen, editor:address:editor-data, t:touch-event -> in-focus?:boolean, editor:address:editor-data [
+recipe move-cursor-in-editor screen:address:shared:screen, editor:address:shared:editor-data, t:touch-event -> in-focus?:boolean, editor:address:shared:editor-data [
   local-scope
   load-ingredients
   reply-unless editor, 0/false
@@ -70,7 +70,7 @@ recipe move-cursor-in-editor screen:address:screen, editor:address:editor-data,
 # Variant of 'render' that only moves the cursor (coordinates and
 # before-cursor). If it's past the end of a line, it 'slides' it left. If it's
 # past the last line it positions at end of last line.
-recipe snap-cursor screen:address:screen, editor:address:editor-data, target-row:number, target-column:number -> editor:address:editor-data [
+recipe snap-cursor screen:address:shared:screen, editor:address:shared:editor-data, target-row:number, target-column:number -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
   reply-unless editor
@@ -78,8 +78,8 @@ recipe snap-cursor screen:address:screen, editor:address:editor-data, target-row
   right:number <- get *editor, right:offset
   screen-height:number <- screen-height screen
   # count newlines until screen row
-  curr:address:duplex-list:character <- get *editor, top-of-screen:offset
-  prev:address:duplex-list:character <- copy curr  # just in case curr becomes null and we can't compute prev
+  curr:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+  prev:address:shared:duplex-list:character <- copy curr  # just in case curr becomes null and we can't compute prev
   curr <- next curr
   row:number <- copy 1/top
   column:number <- copy left
@@ -87,7 +87,7 @@ recipe snap-cursor screen:address:screen, editor:address:editor-data, target-row
   *cursor-row <- copy target-row
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   *cursor-column <- copy target-column
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   {
     +next-character
     break-unless curr
@@ -155,7 +155,7 @@ recipe snap-cursor screen:address:screen, editor:address:editor-data, target-row
 
 # Process an event 'e' and try to minimally update the screen.
 # Set 'go-render?' to true to indicate the caller must perform a non-minimal update.
-recipe handle-keyboard-event screen:address:screen, editor:address:editor-data, e:event -> screen:address:screen, editor:address:editor-data, go-render?:boolean [
+recipe handle-keyboard-event screen:address:shared:screen, editor:address:shared:editor-data, e:event -> screen:address:shared:screen, editor:address:shared:editor-data, go-render?:boolean [
   local-scope
   load-ingredients
   go-render? <- copy 0/false
@@ -164,7 +164,7 @@ recipe handle-keyboard-event screen:address:screen, editor:address:editor-data,
   screen-height:number <- screen-height screen
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   save-row:number <- copy *cursor-row
@@ -195,10 +195,10 @@ recipe handle-keyboard-event screen:address:screen, editor:address:editor-data,
   reply
 ]
 
-recipe insert-at-cursor editor:address:editor-data, c:character, screen:address:screen -> editor:address:editor-data, screen:address:screen, go-render?:boolean [
+recipe insert-at-cursor editor:address:shared:editor-data, c:character, screen:address:shared:screen -> editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean [
   local-scope
   load-ingredients
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   insert c, *before-cursor
   *before-cursor <- next *before-cursor
   cursor-row:address:number <- get-address *editor, cursor-row:offset
@@ -213,7 +213,7 @@ recipe insert-at-cursor editor:address:editor-data, c:character, screen:address:
   <insert-character-special-case>
   # but mostly we'll just move the cursor right
   *cursor-column <- add *cursor-column, 1
-  next:address:duplex-list:character <- next *before-cursor
+  next:address:shared:duplex-list:character <- next *before-cursor
   {
     # at end of all text? no need to scroll? just print the character and leave
     at-end?:boolean <- equal next, 0/null
@@ -233,7 +233,7 @@ recipe insert-at-cursor editor:address:editor-data, c:character, screen:address:
     break-unless next
     at-right?:boolean <- greater-or-equal *cursor-column, screen-width
     break-if at-right?
-    curr:address:duplex-list:character <- copy *before-cursor
+    curr:address:shared:duplex-list:character <- copy *before-cursor
     move-cursor screen, save-row, save-column
     curr-column:number <- copy save-column
     {
@@ -259,7 +259,7 @@ recipe insert-at-cursor editor:address:editor-data, c:character, screen:address:
 ]
 
 # helper for tests
-recipe editor-render screen:address:screen, editor:address:editor-data -> screen:address:screen, editor:address:editor-data [
+recipe editor-render screen:address:shared:screen, editor:address:shared:editor-data -> screen:address:shared:screen, editor:address:shared:editor-data [
   local-scope
   load-ingredients
   left:number <- get *editor, left:offset
@@ -274,12 +274,12 @@ recipe editor-render screen:address:screen, editor:address:editor-data -> screen
 
 scenario editor-handles-empty-event-queue [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console []
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -291,17 +291,17 @@ scenario editor-handles-empty-event-queue [
 
 scenario editor-handles-mouse-clicks [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 1  # on the 'b'
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -318,16 +318,16 @@ scenario editor-handles-mouse-clicks [
 
 scenario editor-handles-mouse-clicks-outside-text [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   $clear-trace
   assume-console [
     left-click 1, 7  # last line, to the right of text
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1  # cursor row
@@ -338,17 +338,17 @@ scenario editor-handles-mouse-clicks-outside-text [
 
 scenario editor-handles-mouse-clicks-outside-text-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   $clear-trace
   assume-console [
     left-click 1, 7  # interior line, to the right of text
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1  # cursor row
@@ -359,17 +359,17 @@ def]
 
 scenario editor-handles-mouse-clicks-outside-text-3 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   $clear-trace
   assume-console [
     left-click 3, 7  # below text
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 2  # cursor row
@@ -380,19 +380,19 @@ def]
 
 scenario editor-handles-mouse-clicks-outside-column [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
+  1:address:shared:array:character <- new [abc]
   # editor occupies only left half of screen
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     # click on right half of screen
     left-click 3, 8
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -409,18 +409,18 @@ scenario editor-handles-mouse-clicks-outside-column [
 
 scenario editor-handles-mouse-clicks-in-menu-area [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     # click on first, 'menu' row
     left-click 0, 3
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # no change to cursor
   memory-should-contain [
@@ -431,15 +431,15 @@ scenario editor-handles-mouse-clicks-in-menu-area [
 
 scenario editor-inserts-characters-into-empty-editor [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     type [abc]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -452,9 +452,9 @@ scenario editor-inserts-characters-into-empty-editor [
 
 scenario editor-inserts-characters-at-cursor [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # type two letters at different places
   assume-console [
@@ -463,7 +463,7 @@ scenario editor-inserts-characters-at-cursor [
     type [d]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -476,16 +476,16 @@ scenario editor-inserts-characters-at-cursor [
 
 scenario editor-inserts-characters-at-cursor-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 5  # right of last line
     type [d]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -498,17 +498,17 @@ scenario editor-inserts-characters-at-cursor-2 [
 
 scenario editor-inserts-characters-at-cursor-5 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 5  # right of non-last line
     type [e]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -522,16 +522,16 @@ d]
 
 scenario editor-inserts-characters-at-cursor-3 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 3, 5  # below all text
     type [d]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -544,17 +544,17 @@ scenario editor-inserts-characters-at-cursor-3 [
 
 scenario editor-inserts-characters-at-cursor-4 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 3, 5  # below all text
     type [e]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -568,17 +568,17 @@ d]
 
 scenario editor-inserts-characters-at-cursor-6 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 3, 5  # below all text
     type [ef]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -592,14 +592,14 @@ d]
 
 scenario editor-moves-cursor-after-inserting-characters [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [ab]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [ab]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [01]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -613,15 +613,15 @@ scenario editor-moves-cursor-after-inserting-characters [
 
 scenario editor-wraps-line-on-insert [
   assume-screen 5/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   # type a letter
   assume-console [
     type [e]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # no wrap yet
   screen-should-contain [
@@ -636,7 +636,7 @@ scenario editor-wraps-line-on-insert [
     type [f]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # now wrap
   screen-should-contain [
@@ -651,19 +651,19 @@ scenario editor-wraps-line-on-insert [
 scenario editor-wraps-line-on-insert-2 [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcdefg
+  1:address:shared:array:character <- new [abcdefg
 defg]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   # type more text at the start
   assume-console [
     left-click 3, 0
     type [abc]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor is not wrapped
   memory-should-contain [
@@ -703,16 +703,16 @@ after <insert-character-special-case> [
 
 scenario editor-wraps-cursor-after-inserting-characters [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcde]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  1:address:shared:array:character <- new [abcde]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   assume-console [
     left-click 1, 4  # line is full; no wrap icon yet
     type [f]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -729,16 +729,16 @@ scenario editor-wraps-cursor-after-inserting-characters [
 
 scenario editor-wraps-cursor-after-inserting-characters-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcde]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  1:address:shared:array:character <- new [abcde]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   assume-console [
     left-click 1, 3  # right before the wrap icon
     type [f]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -755,16 +755,16 @@ scenario editor-wraps-cursor-after-inserting-characters-2 [
 
 scenario editor-wraps-cursor-to-left-margin [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcde]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 2/left, 7/right
+  1:address:shared:array:character <- new [abcde]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 2/left, 7/right
   assume-console [
     left-click 1, 5  # line is full; no wrap icon yet
     type [01]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -792,14 +792,14 @@ after <editor-initialization> [
 
 scenario editor-moves-cursor-down-after-inserting-newline [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   assume-console [
     type [0
 1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -822,12 +822,12 @@ after <handle-special-character> [
   }
 ]
 
-recipe insert-new-line-and-indent editor:address:editor-data, screen:address:screen -> editor:address:editor-data, screen:address:screen, go-render?:boolean [
+recipe insert-new-line-and-indent editor:address:shared:editor-data, screen:address:shared:screen -> editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean [
   local-scope
   load-ingredients
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
   screen-height:number <- screen-height screen
@@ -847,8 +847,8 @@ recipe insert-new-line-and-indent editor:address:editor-data, screen:address:scr
   # indent if necessary
   indent?:boolean <- get *editor, indent?:offset
   reply-unless indent?
-  d:address:duplex-list:character <- get *editor, data:offset
-  end-of-previous-line:address:duplex-list:character <- prev *before-cursor
+  d:address:shared:duplex-list:character <- get *editor, data:offset
+  end-of-previous-line:address:shared:duplex-list:character <- prev *before-cursor
   indent:number <- line-indent end-of-previous-line, d
   i:number <- copy 0
   {
@@ -862,7 +862,7 @@ recipe insert-new-line-and-indent editor:address:editor-data, screen:address:scr
 
 # takes a pointer 'curr' into the doubly-linked list and its sentinel, counts
 # the number of spaces at the start of the line containing 'curr'.
-recipe line-indent curr:address:duplex-list:character, start:address:duplex-list:character -> result:number [
+recipe line-indent curr:address:shared:duplex-list:character, start:address:shared:duplex-list:character -> result:number [
   local-scope
   load-ingredients
   result:number <- copy 0
@@ -894,14 +894,14 @@ recipe line-indent curr:address:duplex-list:character, start:address:duplex-list
 
 scenario editor-moves-cursor-down-after-inserting-newline-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 1/left, 10/right
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 1/left, 10/right
   assume-console [
     type [0
 1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -914,8 +914,8 @@ scenario editor-moves-cursor-down-after-inserting-newline-2 [
 
 scenario editor-clears-previous-line-completely-after-inserting-newline [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcde]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  1:address:shared:array:character <- new [abcde]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   assume-console [
     press enter
   ]
@@ -927,7 +927,7 @@ scenario editor-clears-previous-line-completely-after-inserting-newline [
     .          .
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # line should be fully cleared
   screen-should-contain [
@@ -941,10 +941,10 @@ scenario editor-clears-previous-line-completely-after-inserting-newline [
 
 scenario editor-inserts-indent-after-newline [
   assume-screen 10/width, 10/height
-  1:address:array:character <- new [ab
+  1:address:shared:array:character <- new [ab
   cd
 ef]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # position cursor after 'cd' and hit 'newline'
   assume-console [
     left-click 2, 8
@@ -952,9 +952,9 @@ ef]
 ]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor should be below start of previous line
   memory-should-contain [
@@ -965,10 +965,10 @@ ef]
 
 scenario editor-skips-indent-around-paste [
   assume-screen 10/width, 10/height
-  1:address:array:character <- new [ab
+  1:address:shared:array:character <- new [ab
   cd
 ef]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # position cursor after 'cd' and hit 'newline' surrounded by paste markers
   assume-console [
     left-click 2, 8
@@ -977,9 +977,9 @@ ef]
     press 65506  # end paste
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor should be below start of previous line
   memory-should-contain [
@@ -1012,7 +1012,7 @@ after <handle-special-key> [
 
 ## helpers
 
-recipe draw-horizontal screen:address:screen, row:number, x:number, right:number -> screen:address:screen [
+recipe draw-horizontal screen:address:shared:screen, row:number, x:number, right:number -> screen:address:shared:screen [
   local-scope
   load-ingredients
   style:character, style-found?:boolean <- next-ingredient
diff --git a/edit/003-shortcuts.mu b/edit/003-shortcuts.mu
index feab04ea..b69bf2bd 100644
--- a/edit/003-shortcuts.mu
+++ b/edit/003-shortcuts.mu
@@ -7,14 +7,14 @@
 scenario editor-inserts-two-spaces-on-tab [
   assume-screen 10/width, 5/height
   # just one character in final line
-  1:address:array:character <- new [ab
+  1:address:shared:array:character <- new [ab
 cd]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   assume-console [
     press tab
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -40,18 +40,18 @@ after <handle-special-character> [
 
 scenario editor-handles-backspace-key [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 1
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -71,7 +71,7 @@ after <handle-special-character> [
     delete-previous-character?:boolean <- equal *c, 8/backspace
     break-unless delete-previous-character?
     <backspace-character-begin>
-    editor, screen, go-render?:boolean, backspaced-cell:address:duplex-list:character <- delete-before-cursor editor, screen
+    editor, screen, go-render?:boolean, backspaced-cell:address:shared:duplex-list:character <- delete-before-cursor editor, screen
     <backspace-character-end>
     reply
   }
@@ -80,19 +80,19 @@ after <handle-special-character> [
 # return values:
 #   go-render? - whether caller needs to update the screen
 #   backspaced-cell - value deleted (or 0 if nothing was deleted) so we can save it for undo, etc.
-recipe delete-before-cursor editor:address:editor-data, screen:address:screen -> editor:address:editor-data, screen:address:screen, go-render?:boolean, backspaced-cell:address:duplex-list:character [
+recipe delete-before-cursor editor:address:shared:editor-data, screen:address:shared:screen -> editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean, backspaced-cell:address:shared:duplex-list:character [
   local-scope
   load-ingredients
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
-  data:address:duplex-list:character <- get *editor, data:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
+  data:address:shared:duplex-list:character <- get *editor, data:offset
   # if at start of text (before-cursor at § sentinel), return
-  prev:address:duplex-list:character <- prev *before-cursor
+  prev:address:shared:duplex-list:character <- prev *before-cursor
   go-render?, backspaced-cell <- copy 0/no-more-render, 0/nothing-deleted
   reply-unless prev
   trace 10, [app], [delete-before-cursor]
   original-row:number <- get *editor, cursor-row:offset
   editor, scroll?:boolean <- move-cursor-coordinates-left editor
-  backspaced-cell:address:duplex-list:character <- copy *before-cursor
+  backspaced-cell:address:shared:duplex-list:character <- copy *before-cursor
   data <- remove *before-cursor, data  # will also neatly trim next/prev pointers in backspaced-cell/*before-cursor
   *before-cursor <- copy prev
   go-render? <- copy 1/true
@@ -106,7 +106,7 @@ recipe delete-before-cursor editor:address:editor-data, screen:address:screen ->
   reply-unless same-row?
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
-  curr:address:duplex-list:character <- next *before-cursor
+  curr:address:shared:duplex-list:character <- next *before-cursor
   screen <- move-cursor screen, cursor-row, cursor-column
   curr-column:number <- copy cursor-column
   {
@@ -130,10 +130,10 @@ recipe delete-before-cursor editor:address:editor-data, screen:address:screen ->
   go-render? <- copy 0/false
 ]
 
-recipe move-cursor-coordinates-left editor:address:editor-data -> editor:address:editor-data, go-render?:boolean [
+recipe move-cursor-coordinates-left editor:address:shared:editor-data -> editor:address:shared:editor-data, go-render?:boolean [
   local-scope
   load-ingredients
-  before-cursor:address:duplex-list:character <- get *editor, before-cursor:offset
+  before-cursor:address:shared:duplex-list:character <- get *editor, before-cursor:offset
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   left:number <- get *editor, left:offset
@@ -165,7 +165,7 @@ recipe move-cursor-coordinates-left editor:address:editor-data -> editor:address
     break-unless previous-character-is-newline?
     # compute length of previous line
     trace 10, [app], [switching to previous line]
-    d:address:duplex-list:character <- get *editor, data:offset
+    d:address:shared:duplex-list:character <- get *editor, data:offset
     end-of-line:number <- previous-line-length before-cursor, d
     *cursor-column <- add left, end-of-line
     reply
@@ -178,7 +178,7 @@ recipe move-cursor-coordinates-left editor:address:editor-data -> editor:address
 
 # takes a pointer 'curr' into the doubly-linked list and its sentinel, counts
 # the length of the previous line before the 'curr' pointer.
-recipe previous-line-length curr:address:duplex-list:character, start:address:duplex-list:character -> result:number [
+recipe previous-line-length curr:address:shared:duplex-list:character, start:address:shared:duplex-list:character -> result:number [
   local-scope
   load-ingredients
   result:number <- copy 0
@@ -201,17 +201,17 @@ recipe previous-line-length curr:address:duplex-list:character, start:address:du
 scenario editor-clears-last-line-on-backspace [
   assume-screen 10/width, 5/height
   # just one character in final line
-  1:address:array:character <- new [ab
+  1:address:shared:array:character <- new [ab
 cd]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   assume-console [
     left-click 2, 0  # cursor at only character in final line
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -228,10 +228,10 @@ cd]
 scenario editor-joins-and-wraps-lines-on-backspace [
   assume-screen 10/width, 5/height
   # initialize editor with two long-ish but non-wrapping lines
-  1:address:array:character <- new [abc def
+  1:address:shared:array:character <- new [abc def
 ghi jkl]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # position the cursor at the start of the second and hit backspace
   assume-console [
@@ -239,7 +239,7 @@ ghi jkl]
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # resulting single line should wrap correctly
   screen-should-contain [
@@ -254,9 +254,9 @@ ghi jkl]
 scenario editor-wraps-long-lines-on-backspace [
   assume-screen 10/width, 5/height
   # initialize editor in part of the screen with a long line
-  1:address:array:character <- new [abc def ghij]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 8/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc def ghij]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 8/right
+  editor-render screen, 2:address:shared:editor-data
   # confirm that it wraps
   screen-should-contain [
     .          .
@@ -271,7 +271,7 @@ scenario editor-wraps-long-lines-on-backspace [
     press backspace
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # resulting single line should wrap correctly and not overflow its bounds
   screen-should-contain [
@@ -287,15 +287,15 @@ scenario editor-wraps-long-lines-on-backspace [
 
 scenario editor-handles-delete-key [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     press delete
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -309,7 +309,7 @@ scenario editor-handles-delete-key [
     press delete
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -325,18 +325,18 @@ after <handle-special-key> [
     delete-next-character?:boolean <- equal *k, 65522/delete
     break-unless delete-next-character?
     <delete-character-begin>
-    editor, screen, go-render?:boolean, deleted-cell:address:duplex-list:character <- delete-at-cursor editor, screen
+    editor, screen, go-render?:boolean, deleted-cell:address:shared:duplex-list:character <- delete-at-cursor editor, screen
     <delete-character-end>
     reply
   }
 ]
 
-recipe delete-at-cursor editor:address:editor-data, screen:address:screen -> editor:address:editor-data, screen:address:screen, go-render?:boolean, deleted-cell:address:duplex-list:character [
+recipe delete-at-cursor editor:address:shared:editor-data, screen:address:shared:screen -> editor:address:shared:editor-data, screen:address:shared:screen, go-render?:boolean, deleted-cell:address:shared:duplex-list:character [
   local-scope
   load-ingredients
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
-  data:address:duplex-list:character <- get *editor, data:offset
-  deleted-cell:address:duplex-list:character <- next *before-cursor
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
+  data:address:shared:duplex-list:character <- get *editor, data:offset
+  deleted-cell:address:shared:duplex-list:character <- next *before-cursor
   go-render? <- copy 0/false
   reply-unless deleted-cell
   currc:character <- get *deleted-cell, value:offset
@@ -345,7 +345,7 @@ recipe delete-at-cursor editor:address:editor-data, screen:address:screen -> edi
   go-render? <- copy 1/true
   reply-if deleted-newline?
   # wasn't a newline? render rest of line
-  curr:address:duplex-list:character <- next *before-cursor  # refresh after remove above
+  curr:address:shared:duplex-list:character <- next *before-cursor  # refresh after remove above
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   screen <- move-cursor screen, *cursor-row, *cursor-column
@@ -376,16 +376,16 @@ recipe delete-at-cursor editor:address:editor-data, screen:address:screen -> edi
 
 scenario editor-moves-cursor-right-with-key [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     press right-arrow
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -401,7 +401,7 @@ after <handle-special-key> [
     move-to-next-character?:boolean <- equal *k, 65514/right-arrow
     break-unless move-to-next-character?
     # if not at end of text
-    next-cursor:address:duplex-list:character <- next *before-cursor
+    next-cursor:address:shared:duplex-list:character <- next *before-cursor
     break-unless next-cursor
     # scan to next character
     <move-cursor-begin>
@@ -414,10 +414,10 @@ after <handle-special-key> [
   }
 ]
 
-recipe move-cursor-coordinates-right editor:address:editor-data, screen-height:number -> editor:address:editor-data, go-render?:boolean [
+recipe move-cursor-coordinates-right editor:address:shared:editor-data, screen-height:number -> editor:address:shared:editor-data, go-render?:boolean [
   local-scope
   load-ingredients
-  before-cursor:address:duplex-list:character <- get *editor before-cursor:offset
+  before-cursor:address:shared:duplex-list:character <- get *editor before-cursor:offset
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   left:number <- get *editor, left:offset
@@ -444,7 +444,7 @@ recipe move-cursor-coordinates-right editor:address:editor-data, screen-height:n
     at-wrap?:boolean <- equal *cursor-column, wrap-column
     break-unless at-wrap?
     # and if next character isn't newline
-    next:address:duplex-list:character <- next before-cursor
+    next:address:shared:duplex-list:character <- next before-cursor
     break-unless next
     next-character:character <- get *next, value:offset
     newline?:boolean <- equal next-character, 10/newline
@@ -465,10 +465,10 @@ recipe move-cursor-coordinates-right editor:address:editor-data, screen-height:n
 
 scenario editor-moves-cursor-to-next-line-with-right-arrow [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # type right-arrow a few times to get to start of second line
   assume-console [
@@ -478,7 +478,7 @@ d]
     press right-arrow  # next line
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   check-trace-count-for-label 0, [print-character]
   # type something and ensure it goes where it should
@@ -486,7 +486,7 @@ d]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -500,10 +500,10 @@ d]
 
 scenario editor-moves-cursor-to-next-line-with-right-arrow-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 1/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 1/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     press right-arrow
     press right-arrow
@@ -512,7 +512,7 @@ d]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -525,18 +525,18 @@ d]
 
 scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcdef]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abcdef]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 3
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -555,9 +555,9 @@ scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow [
 scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
   assume-screen 10/width, 5/height
   # line just barely wrapping
-  1:address:array:character <- new [abcde]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abcde]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # position cursor at last character before wrap and hit right-arrow
   assume-console [
@@ -565,9 +565,9 @@ scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 2
@@ -578,9 +578,9 @@ scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 2
@@ -591,18 +591,18 @@ scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow-2 [
 
 scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow-3 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abcdef]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 1/left, 6/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abcdef]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 1/left, 6/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 4
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .          .
@@ -620,10 +620,10 @@ scenario editor-moves-cursor-to-next-wrapped-line-with-right-arrow-3 [
 
 scenario editor-moves-cursor-to-next-line-with-right-arrow-at-end-of-line [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # move to end of line, press right-arrow, type a character
   assume-console [
@@ -632,7 +632,7 @@ d]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # new character should be in next line
   screen-should-contain [
@@ -651,9 +651,9 @@ d]
 
 scenario editor-moves-cursor-left-with-key [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 2
@@ -661,7 +661,7 @@ scenario editor-moves-cursor-left-with-key [
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -678,7 +678,7 @@ after <handle-special-key> [
     break-unless move-to-previous-character?
     trace 10, [app], [left arrow]
     # if not at start of text (before-cursor at § sentinel)
-    prev:address:duplex-list:character <- prev *before-cursor
+    prev:address:shared:duplex-list:character <- prev *before-cursor
     go-render? <- copy 0/false
     reply-unless prev
     <move-cursor-begin>
@@ -693,10 +693,10 @@ after <handle-special-key> [
 scenario editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line [
   assume-screen 10/width, 5/height
   # initialize editor with two lines
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # position cursor at start of second line (so there's no previous newline)
   assume-console [
@@ -704,9 +704,9 @@ d]
     press left-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1
@@ -718,11 +718,11 @@ d]
 scenario editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-2 [
   assume-screen 10/width, 5/height
   # initialize editor with three lines
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 g]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # position cursor further down (so there's a newline before the character at
   # the cursor)
@@ -732,7 +732,7 @@ g]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -746,11 +746,11 @@ g]
 
 scenario editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-3 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 g]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # position cursor at start of text, press left-arrow, then type a character
   assume-console [
@@ -759,7 +759,7 @@ g]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # left-arrow should have had no effect
   screen-should-contain [
@@ -775,11 +775,11 @@ g]
 scenario editor-moves-cursor-to-previous-line-with-left-arrow-at-start-of-line-4 [
   assume-screen 10/width, 5/height
   # initialize editor with text containing an empty line
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # position cursor right after empty line
   assume-console [
@@ -788,7 +788,7 @@ d]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -803,9 +803,9 @@ d]
 scenario editor-moves-across-screen-lines-across-wrap-with-left-arrow [
   assume-screen 10/width, 5/height
   # initialize editor with text containing an empty line
-  1:address:array:character <- new [abcdef]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [abcdef]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   screen-should-contain [
     .          .
@@ -820,9 +820,9 @@ scenario editor-moves-across-screen-lines-across-wrap-with-left-arrow [
     press left-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1  # previous row
@@ -837,19 +837,19 @@ scenario editor-moves-across-screen-lines-across-wrap-with-left-arrow [
 
 scenario editor-moves-to-previous-line-with-up-arrow [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 2, 1
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1
@@ -860,7 +860,7 @@ def]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -883,12 +883,12 @@ after <handle-special-key> [
   }
 ]
 
-recipe move-to-previous-line editor:address:editor-data -> editor:address:editor-data, go-render?:boolean [
+recipe move-to-previous-line editor:address:shared:editor-data -> editor:address:shared:editor-data, go-render?:boolean [
   local-scope
   load-ingredients
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
   already-at-top?:boolean <- lesser-or-equal *cursor-row, 1/top
@@ -898,13 +898,13 @@ recipe move-to-previous-line editor:address:editor-data -> editor:address:editor
     # if not at newline, move to start of line (previous newline)
     # then scan back another line
     # if either step fails, give up without modifying cursor or coordinates
-    curr:address:duplex-list:character <- copy *before-cursor
+    curr:address:shared:duplex-list:character <- copy *before-cursor
     {
-      old:address:duplex-list:character <- copy curr
+      old:address:shared:duplex-list:character <- copy curr
       c2:character <- get *curr, value:offset
       at-newline?:boolean <- equal c2, 10/newline
       break-if at-newline?
-      curr:address:duplex-list:character <- before-previous-line curr, editor
+      curr:address:shared:duplex-list:character <- before-previous-line curr, editor
       no-motion?:boolean <- equal curr, old
       go-render? <- copy 0/false
       reply-if no-motion?
@@ -924,7 +924,7 @@ recipe move-to-previous-line editor:address:editor-data -> editor:address:editor
     {
       done?:boolean <- greater-or-equal *cursor-column, target-column
       break-if done?
-      curr:address:duplex-list:character <- next *before-cursor
+      curr:address:shared:duplex-list:character <- next *before-cursor
       break-unless curr
       currc:character <- get *curr, value:offset
       at-newline?:boolean <- equal currc, 10/newline
@@ -948,19 +948,19 @@ recipe move-to-previous-line editor:address:editor-data -> editor:address:editor
 
 scenario editor-adjusts-column-at-previous-line [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [ab
+  1:address:shared:array:character <- new [ab
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 2, 3
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1
@@ -971,7 +971,7 @@ def]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -984,19 +984,19 @@ def]
 
 scenario editor-adjusts-column-at-empty-line [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [
+  1:address:shared:array:character <- new [
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 2, 3
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 1
@@ -1007,7 +1007,7 @@ def]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1021,11 +1021,11 @@ def]
 scenario editor-moves-to-previous-line-from-left-margin [
   assume-screen 10/width, 5/height
   # start out with three lines
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # click on the third line and hit up-arrow, so you end up just after a newline
   assume-console [
@@ -1033,9 +1033,9 @@ ghi]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 2
@@ -1046,7 +1046,7 @@ ghi]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1061,19 +1061,19 @@ ghi]
 
 scenario editor-moves-to-next-line-with-down-arrow [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # cursor starts out at (1, 0)
   assume-console [
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # ..and ends at (2, 0)
   memory-should-contain [
@@ -1085,7 +1085,7 @@ def]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1108,12 +1108,12 @@ after <handle-special-key> [
   }
 ]
 
-recipe move-to-next-line editor:address:editor-data, screen-height:number -> editor:address:editor-data, go-render?:boolean [
+recipe move-to-next-line editor:address:shared:editor-data, screen-height:number -> editor:address:shared:editor-data, go-render?:boolean [
   local-scope
   load-ingredients
   cursor-row:address:number <- get-address *editor, cursor-row:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
   last-line:number <- subtract screen-height, 1
@@ -1123,7 +1123,7 @@ recipe move-to-next-line editor:address:editor-data, screen-height:number -> edi
     break-if already-at-bottom?
     # scan to start of next line, then to right column or until end of line
     max:number <- subtract right, left
-    next-line:address:duplex-list:character <- before-start-of-next-line *before-cursor, max
+    next-line:address:shared:duplex-list:character <- before-start-of-next-line *before-cursor, max
     {
       # already at end of buffer? try to scroll up (so we can see more
       # warnings or sandboxes below)
@@ -1141,7 +1141,7 @@ recipe move-to-next-line editor:address:editor-data, screen-height:number -> edi
     {
       done?:boolean <- greater-or-equal *cursor-column, target-column
       break-if done?
-      curr:address:duplex-list:character <- next *before-cursor
+      curr:address:shared:duplex-list:character <- next *before-cursor
       break-unless curr
       currc:character <- get *curr, value:offset
       at-newline?:boolean <- equal currc, 10/newline
@@ -1161,19 +1161,19 @@ recipe move-to-next-line editor:address:editor-data, screen-height:number -> edi
 
 scenario editor-adjusts-column-at-next-line [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 de]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   assume-console [
     left-click 1, 3
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     3 <- 2
@@ -1184,7 +1184,7 @@ de]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1199,10 +1199,10 @@ de]
 
 scenario editor-moves-to-start-of-line-with-ctrl-a [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on second line, press ctrl-a
   assume-console [
@@ -1210,9 +1210,9 @@ scenario editor-moves-to-start-of-line-with-ctrl-a [
     press ctrl-a
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to start of line
   memory-should-contain [
@@ -1248,7 +1248,7 @@ after <handle-special-key> [
   }
 ]
 
-recipe move-to-start-of-line editor:address:editor-data -> editor:address:editor-data [
+recipe move-to-start-of-line editor:address:shared:editor-data -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
   # update cursor column
@@ -1256,8 +1256,8 @@ recipe move-to-start-of-line editor:address:editor-data -> editor:address:editor
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   *cursor-column <- copy left
   # update before-cursor
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
-  init:address:duplex-list:character <- get *editor, data:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
+  init:address:shared:duplex-list:character <- get *editor, data:offset
   # while not at start of line, move 
   {
     at-start-of-text?:boolean <- equal *before-cursor, init
@@ -1273,10 +1273,10 @@ recipe move-to-start-of-line editor:address:editor-data -> editor:address:editor
 
 scenario editor-moves-to-start-of-line-with-ctrl-a-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on first line (no newline before), press ctrl-a
   assume-console [
@@ -1284,9 +1284,9 @@ scenario editor-moves-to-start-of-line-with-ctrl-a-2 [
     press ctrl-a
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to start of line
   memory-should-contain [
@@ -1298,9 +1298,9 @@ scenario editor-moves-to-start-of-line-with-ctrl-a-2 [
 
 scenario editor-moves-to-start-of-line-with-home [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   $clear-trace
   # start on second line, press 'home'
   assume-console [
@@ -1308,9 +1308,9 @@ scenario editor-moves-to-start-of-line-with-home [
     press home
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to start of line
   memory-should-contain [
@@ -1322,10 +1322,10 @@ scenario editor-moves-to-start-of-line-with-home [
 
 scenario editor-moves-to-start-of-line-with-home-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on first line (no newline before), press 'home'
   assume-console [
@@ -1333,9 +1333,9 @@ scenario editor-moves-to-start-of-line-with-home-2 [
     press home
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to start of line
   memory-should-contain [
@@ -1349,10 +1349,10 @@ scenario editor-moves-to-start-of-line-with-home-2 [
 
 scenario editor-moves-to-end-of-line-with-ctrl-e [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on first line, press ctrl-e
   assume-console [
@@ -1360,9 +1360,9 @@ scenario editor-moves-to-end-of-line-with-ctrl-e [
     press ctrl-e
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to end of line
   memory-should-contain [
@@ -1375,9 +1375,9 @@ scenario editor-moves-to-end-of-line-with-ctrl-e [
     type [z]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     4 <- 1
@@ -1419,14 +1419,14 @@ after <handle-special-key> [
   }
 ]
 
-recipe move-to-end-of-line editor:address:editor-data -> editor:address:editor-data [
+recipe move-to-end-of-line editor:address:shared:editor-data -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   cursor-column:address:number <- get-address *editor, cursor-column:offset
   # while not at start of line, move 
   {
-    next:address:duplex-list:character <- next *before-cursor
+    next:address:shared:duplex-list:character <- next *before-cursor
     break-unless next  # end of text
     nextc:character <- get *next, value:offset
     at-end-of-line?:boolean <- equal nextc, 10/newline
@@ -1439,10 +1439,10 @@ recipe move-to-end-of-line editor:address:editor-data -> editor:address:editor-d
 
 scenario editor-moves-to-end-of-line-with-ctrl-e-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on second line (no newline after), press ctrl-e
   assume-console [
@@ -1450,9 +1450,9 @@ scenario editor-moves-to-end-of-line-with-ctrl-e-2 [
     press ctrl-e
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    4:number <- get *2:address:editor-data, cursor-row:offset
-    5:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    4:number <- get *2:address:shared:editor-data, cursor-row:offset
+    5:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to end of line
   memory-should-contain [
@@ -1464,10 +1464,10 @@ scenario editor-moves-to-end-of-line-with-ctrl-e-2 [
 
 scenario editor-moves-to-end-of-line-with-end [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on first line, press 'end'
   assume-console [
@@ -1475,9 +1475,9 @@ scenario editor-moves-to-end-of-line-with-end [
     press end
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to end of line
   memory-should-contain [
@@ -1489,10 +1489,10 @@ scenario editor-moves-to-end-of-line-with-end [
 
 scenario editor-moves-to-end-of-line-with-end-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # start on second line (no newline after), press 'end'
   assume-console [
@@ -1500,9 +1500,9 @@ scenario editor-moves-to-end-of-line-with-end-2 [
     press end
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to end of line
   memory-should-contain [
@@ -1516,16 +1516,16 @@ scenario editor-moves-to-end-of-line-with-end-2 [
 
 scenario editor-deletes-to-start-of-line-with-ctrl-u [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start on second line, press ctrl-u
   assume-console [
     left-click 2, 2
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes to start of line
   screen-should-contain [
@@ -1542,21 +1542,21 @@ after <handle-special-character> [
     delete-to-start-of-line?:boolean <- equal *c, 21/ctrl-u
     break-unless delete-to-start-of-line?
     <delete-to-start-of-line-begin>
-    deleted-cells:address:duplex-list:character <- delete-to-start-of-line editor
+    deleted-cells:address:shared:duplex-list:character <- delete-to-start-of-line editor
     <delete-to-start-of-line-end>
     go-render? <- copy 1/true
     reply
   }
 ]
 
-recipe delete-to-start-of-line editor:address:editor-data -> result:address:duplex-list:character, editor:address:editor-data [
+recipe delete-to-start-of-line editor:address:shared:editor-data -> result:address:shared:duplex-list:character, editor:address:shared:editor-data [
   local-scope
   load-ingredients
   # compute range to delete
-  init:address:duplex-list:character <- get *editor, data:offset
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
-  start:address:duplex-list:character <- copy *before-cursor
-  end:address:duplex-list:character <- next *before-cursor
+  init:address:shared:duplex-list:character <- get *editor, data:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
+  start:address:shared:duplex-list:character <- copy *before-cursor
+  end:address:shared:duplex-list:character <- next *before-cursor
   {
     at-start-of-text?:boolean <- equal start, init
     break-if at-start-of-text?
@@ -1568,7 +1568,7 @@ recipe delete-to-start-of-line editor:address:editor-data -> result:address:dupl
     loop
   }
   # snip it out
-  result:address:duplex-list:character <- next start
+  result:address:shared:duplex-list:character <- next start
   remove-between start, end
   # adjust cursor
   *before-cursor <- copy start
@@ -1579,16 +1579,16 @@ recipe delete-to-start-of-line editor:address:editor-data -> result:address:dupl
 
 scenario editor-deletes-to-start-of-line-with-ctrl-u-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start on first line (no newline before), press ctrl-u
   assume-console [
     left-click 1, 2
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes to start of line
   screen-should-contain [
@@ -1602,16 +1602,16 @@ scenario editor-deletes-to-start-of-line-with-ctrl-u-2 [
 
 scenario editor-deletes-to-start-of-line-with-ctrl-u-3 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start past end of line, press ctrl-u
   assume-console [
     left-click 1, 3
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes to start of line
   screen-should-contain [
@@ -1625,16 +1625,16 @@ scenario editor-deletes-to-start-of-line-with-ctrl-u-3 [
 
 scenario editor-deletes-to-start-of-final-line-with-ctrl-u [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start past end of final line, press ctrl-u
   assume-console [
     left-click 2, 3
     press ctrl-u
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes to start of line
   screen-should-contain [
@@ -1650,16 +1650,16 @@ scenario editor-deletes-to-start-of-final-line-with-ctrl-u [
 
 scenario editor-deletes-to-end-of-line-with-ctrl-k [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start on first line, press ctrl-k
   assume-console [
     left-click 1, 1
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes to end of line
   screen-should-contain [
@@ -1676,19 +1676,19 @@ after <handle-special-character> [
     delete-to-end-of-line?:boolean <- equal *c, 11/ctrl-k
     break-unless delete-to-end-of-line?
     <delete-to-end-of-line-begin>
-    deleted-cells:address:duplex-list:character <- delete-to-end-of-line editor
+    deleted-cells:address:shared:duplex-list:character <- delete-to-end-of-line editor
     <delete-to-end-of-line-end>
     go-render? <- copy 1/true
     reply
   }
 ]
 
-recipe delete-to-end-of-line editor:address:editor-data -> result:address:duplex-list:character, editor:address:editor-data [
+recipe delete-to-end-of-line editor:address:shared:editor-data -> result:address:shared:duplex-list:character, editor:address:shared:editor-data [
   local-scope
   load-ingredients
   # compute range to delete
-  start:address:duplex-list:character <- get *editor, before-cursor:offset
-  end:address:duplex-list:character <- next start
+  start:address:shared:duplex-list:character <- get *editor, before-cursor:offset
+  end:address:shared:duplex-list:character <- next start
   {
     at-end-of-text?:boolean <- equal end, 0/null
     break-if at-end-of-text?
@@ -1705,16 +1705,16 @@ recipe delete-to-end-of-line editor:address:editor-data -> result:address:duplex
 
 scenario editor-deletes-to-end-of-line-with-ctrl-k-2 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start on second line (no newline after), press ctrl-k
   assume-console [
     left-click 2, 1
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes to end of line
   screen-should-contain [
@@ -1728,16 +1728,16 @@ scenario editor-deletes-to-end-of-line-with-ctrl-k-2 [
 
 scenario editor-deletes-to-end-of-line-with-ctrl-k-3 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start at end of line
   assume-console [
     left-click 1, 2
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes just last character
   screen-should-contain [
@@ -1751,16 +1751,16 @@ scenario editor-deletes-to-end-of-line-with-ctrl-k-3 [
 
 scenario editor-deletes-to-end-of-line-with-ctrl-k-4 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start past end of line
   assume-console [
     left-click 1, 3
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes nothing
   screen-should-contain [
@@ -1774,16 +1774,16 @@ scenario editor-deletes-to-end-of-line-with-ctrl-k-4 [
 
 scenario editor-deletes-to-end-of-line-with-ctrl-k-5 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start at end of text
   assume-console [
     left-click 2, 2
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes just the final character
   screen-should-contain [
@@ -1797,16 +1797,16 @@ scenario editor-deletes-to-end-of-line-with-ctrl-k-5 [
 
 scenario editor-deletes-to-end-of-line-with-ctrl-k-6 [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [123
+  1:address:shared:array:character <- new [123
 456]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   # start past end of text
   assume-console [
     left-click 2, 3
     press ctrl-k
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # cursor deletes nothing
   screen-should-contain [
@@ -1824,11 +1824,11 @@ scenario editor-can-scroll-down-using-arrow-keys [
   # screen has 1 line for menu + 3 lines
   assume-screen 10/width, 4/height
   # initialize editor with >3 lines
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   screen-should-contain [
     .          .
     .a         .
@@ -1841,7 +1841,7 @@ d]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen slides by one line
   screen-should-contain [
@@ -1854,11 +1854,11 @@ d]
 
 after <scroll-down> [
   trace 10, [app], [scroll down]
-  top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+  top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
   max:number <- subtract right, left
-  old-top:address:duplex-list:character <- copy *top-of-screen
+  old-top:address:shared:duplex-list:character <- copy *top-of-screen
   *top-of-screen <- before-start-of-next-line *top-of-screen, max
   no-movement?:boolean <- equal old-top, *top-of-screen
   go-render? <- copy 0/false
@@ -1868,11 +1868,11 @@ after <scroll-down> [
 # takes a pointer into the doubly-linked list, scans ahead at most 'max'
 # positions until the next newline
 # beware: never return null pointer.
-recipe before-start-of-next-line original:address:duplex-list:character, max:number -> curr:address:duplex-list:character [
+recipe before-start-of-next-line original:address:shared:duplex-list:character, max:number -> curr:address:shared:duplex-list:character [
   local-scope
   load-ingredients
   count:number <- copy 0
-  curr:address:duplex-list:character <- copy original
+  curr:address:shared:duplex-list:character <- copy original
   # skip the initial newline if it exists
   {
     c:character <- get *curr, value:offset
@@ -1901,11 +1901,11 @@ scenario editor-scrolls-down-past-wrapped-line-using-arrow-keys [
   assume-screen 10/width, 4/height
   # initialize editor with a long, wrapped line and more than a screen of
   # other lines
-  1:address:array:character <- new [abcdef
+  1:address:shared:array:character <- new [abcdef
 g
 h
 i]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   screen-should-contain [
     .          .
     .abcd↩     .
@@ -1918,7 +1918,7 @@ i]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -1933,18 +1933,18 @@ scenario editor-scrolls-down-past-wrapped-line-using-arrow-keys-2 [
   # screen has 1 line for menu + 3 lines
   assume-screen 10/width, 4/height
   # editor starts with a long line wrapping twice
-  1:address:array:character <- new [abcdefghij
+  1:address:shared:array:character <- new [abcdefghij
 k
 l
 m]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at last line, then try to move further down
   assume-console [
     left-click 3, 0
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line containing a wrap icon
   screen-should-contain [
@@ -1958,7 +1958,7 @@ m]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -1973,19 +1973,19 @@ scenario editor-scrolls-down-when-line-wraps [
   # screen has 1 line for menu + 3 lines
   assume-screen 5/width, 4/height
   # editor contains a long line in the third line
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 cdef]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at end, type a character
   assume-console [
     left-click 3, 4
     type [g]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen scrolls
   screen-should-contain [
@@ -2003,19 +2003,19 @@ cdef]
 scenario editor-scrolls-down-on-newline [
   assume-screen 5/width, 4/height
   # position cursor after last line and type newline
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   assume-console [
     left-click 3, 4
     type [
 ]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen scrolls
   screen-should-contain [
@@ -2034,19 +2034,19 @@ scenario editor-scrolls-down-on-right-arrow [
   # screen has 1 line for menu + 3 lines
   assume-screen 5/width, 4/height
   # editor contains a wrapped line
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 cdefgh]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at end of screen and try to move right
   assume-console [
     left-click 3, 3
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen scrolls
   screen-should-contain [
@@ -2065,20 +2065,20 @@ scenario editor-scrolls-down-on-right-arrow-2 [
   # screen has 1 line for menu + 3 lines
   assume-screen 5/width, 4/height
   # editor contains more lines than can fit on screen
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at end of screen and try to move right
   assume-console [
     left-click 3, 3
     press right-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen scrolls
   screen-should-contain [
@@ -2095,10 +2095,10 @@ d]
 
 scenario editor-scrolls-at-end-on-down-arrow [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 de]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   $clear-trace
   # try to move down past end of text
   assume-console [
@@ -2106,9 +2106,9 @@ de]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen should scroll, moving cursor to end of text
   memory-should-contain [
@@ -2119,7 +2119,7 @@ de]
     type [0]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2134,9 +2134,9 @@ de]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen stops scrolling because cursor is already at top
   memory-should-contain [
@@ -2148,7 +2148,7 @@ de]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2162,14 +2162,14 @@ scenario editor-combines-page-and-line-scroll [
   # screen has 1 line for menu + 3 lines
   assume-screen 10/width, 4/height
   # initialize editor with a few pages of lines
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
 e
 f
 g]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # scroll down one page and one line
   assume-console [
     press page-down
@@ -2177,7 +2177,7 @@ g]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen scrolls down 3 lines
   screen-should-contain [
@@ -2194,11 +2194,11 @@ scenario editor-can-scroll-up-using-arrow-keys [
   # screen has 1 line for menu + 3 lines
   assume-screen 10/width, 4/height
   # initialize editor with >3 lines
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   screen-should-contain [
     .          .
     .a         .
@@ -2211,7 +2211,7 @@ d]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen slides by one line
   screen-should-contain [
@@ -2224,8 +2224,8 @@ d]
 
 after <scroll-up> [
   trace 10, [app], [scroll up]
-  top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
-  old-top:address:duplex-list:character <- copy *top-of-screen
+  top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
+  old-top:address:shared:duplex-list:character <- copy *top-of-screen
   *top-of-screen <- before-previous-line *top-of-screen, editor
   no-movement?:boolean <- equal old-top, *top-of-screen
   go-render? <- copy 0/false
@@ -2235,7 +2235,7 @@ after <scroll-up> [
 # takes a pointer into the doubly-linked list, scans back to before start of
 # previous *wrapped* line
 # beware: never return null pointer
-recipe before-previous-line curr:address:duplex-list:character, editor:address:editor-data -> curr:address:duplex-list:character [
+recipe before-previous-line curr:address:shared:duplex-list:character, editor:address:shared:editor-data -> curr:address:shared:duplex-list:character [
   local-scope
   load-ingredients
   c:character <- get *curr, value:offset
@@ -2245,12 +2245,12 @@ recipe before-previous-line curr:address:duplex-list:character, editor:address:e
   left:number <- get *editor, left:offset
   right:number <- get *editor, right:offset
   max-line-length:number <- subtract right, left, -1/exclusive-right, 1/wrap-icon
-  sentinel:address:duplex-list:character <- get *editor, data:offset
+  sentinel:address:shared:duplex-list:character <- get *editor, data:offset
   len:number <- previous-line-length curr, sentinel
   {
     break-if len
     # empty line; just skip this newline
-    prev:address:duplex-list:character <- prev curr
+    prev:address:shared:duplex-list:character <- prev curr
     reply-unless prev, curr
     reply prev
   }
@@ -2266,7 +2266,7 @@ recipe before-previous-line curr:address:duplex-list:character, editor:address:e
   {
     done?:boolean <- greater-or-equal count, max
     break-if done?
-    prev:address:duplex-list:character <- prev curr
+    prev:address:shared:duplex-list:character <- prev curr
     break-unless prev
     curr <- copy prev
     count <- add count, 1
@@ -2280,11 +2280,11 @@ scenario editor-scrolls-up-past-wrapped-line-using-arrow-keys [
   assume-screen 10/width, 4/height
   # initialize editor with a long, wrapped line and more than a screen of
   # other lines
-  1:address:array:character <- new [abcdef
+  1:address:shared:array:character <- new [abcdef
 g
 h
 i]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   screen-should-contain [
     .          .
     .abcd↩     .
@@ -2296,7 +2296,7 @@ i]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2309,7 +2309,7 @@ i]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -2324,17 +2324,17 @@ scenario editor-scrolls-up-past-wrapped-line-using-arrow-keys-2 [
   # screen has 1 line for menu + 4 lines
   assume-screen 10/width, 5/height
   # editor starts with a long line wrapping twice, occupying 3 of the 4 lines
-  1:address:array:character <- new [abcdefghij
+  1:address:shared:array:character <- new [abcdefghij
 k
 l
 m]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at top of second page
   assume-console [
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2348,7 +2348,7 @@ m]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -2363,7 +2363,7 @@ m]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -2378,7 +2378,7 @@ m]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -2397,11 +2397,11 @@ scenario editor-scrolls-up-past-wrapped-line-using-arrow-keys-3 [
   assume-screen 10/width, 4/height
   # initialize editor with a long, wrapped line and more than a screen of
   # other lines
-  1:address:array:character <- new [abcdef
+  1:address:shared:array:character <- new [abcdef
 g
 h
 i]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 6/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 6/right
   screen-should-contain [
     .          .
     .abcde↩    .
@@ -2413,7 +2413,7 @@ i]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2426,7 +2426,7 @@ i]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows partial wrapped line
   screen-should-contain [
@@ -2441,18 +2441,18 @@ i]
 scenario editor-scrolls-up-past-wrapped-line-using-arrow-keys-4 [
   assume-screen 10/width, 4/height
   # initialize editor with some lines around an empty line
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 
 c
 d
 e]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 6/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 6/right
   assume-console [
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2464,7 +2464,7 @@ e]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2476,7 +2476,7 @@ e]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2490,18 +2490,18 @@ scenario editor-scrolls-up-on-left-arrow [
   # screen has 1 line for menu + 3 lines
   assume-screen 5/width, 4/height
   # editor contains >3 lines
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
 e]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at top of second page
   assume-console [
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .     .
@@ -2514,9 +2514,9 @@ e]
     press left-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen scrolls
   screen-should-contain [
@@ -2535,11 +2535,11 @@ scenario editor-can-scroll-up-to-start-of-file [
   # screen has 1 line for menu + 3 lines
   assume-screen 10/width, 4/height
   # initialize editor with >3 lines
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   screen-should-contain [
     .          .
     .a         .
@@ -2554,7 +2554,7 @@ d]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen slides by one line
   screen-should-contain [
@@ -2568,7 +2568,7 @@ d]
     press up-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen remains unchanged
   screen-should-contain [
@@ -2583,11 +2583,11 @@ d]
 
 scenario editor-can-scroll [
   assume-screen 10/width, 4/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   screen-should-contain [
     .          .
     .a         .
@@ -2599,7 +2599,7 @@ d]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows next page
   screen-should-contain [
@@ -2614,8 +2614,8 @@ after <handle-special-character> [
   {
     page-down?:boolean <- equal *c, 6/ctrl-f
     break-unless page-down?
-    top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
-    old-top:address:duplex-list:character <- copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
+    old-top:address:shared:duplex-list:character <- copy *top-of-screen
     <move-cursor-begin>
     page-down editor
     undo-coalesce-tag:number <- copy 0/never
@@ -2630,8 +2630,8 @@ after <handle-special-key> [
   {
     page-down?:boolean <- equal *k, 65518/page-down
     break-unless page-down?
-    top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
-    old-top:address:duplex-list:character <- copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
+    old-top:address:shared:duplex-list:character <- copy *top-of-screen
     <move-cursor-begin>
     page-down editor
     undo-coalesce-tag:number <- copy 0/never
@@ -2644,14 +2644,14 @@ after <handle-special-key> [
 
 # page-down skips entire wrapped lines, so it can't scroll past lines
 # taking up the entire screen
-recipe page-down editor:address:editor-data -> editor:address:editor-data [
+recipe page-down editor:address:shared:editor-data -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
   # if editor contents don't overflow screen, do nothing
-  bottom-of-screen:address:duplex-list:character <- get *editor, bottom-of-screen:offset
+  bottom-of-screen:address:shared:duplex-list:character <- get *editor, bottom-of-screen:offset
   reply-unless bottom-of-screen
   # if not, position cursor at final character
-  before-cursor:address:address:duplex-list:character <- get-address *editor, before-cursor:offset
+  before-cursor:address:address:shared:duplex-list:character <- get-address *editor, before-cursor:offset
   *before-cursor <- prev bottom-of-screen
   # keep one line in common with previous page
   {
@@ -2662,16 +2662,16 @@ recipe page-down editor:address:editor-data -> editor:address:editor-data [
   }
   # move cursor and top-of-screen to start of that line
   move-to-start-of-line editor
-  top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+  top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
   *top-of-screen <- copy *before-cursor
 ]
 
 scenario editor-does-not-scroll-past-end [
   assume-screen 10/width, 4/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .a         .
@@ -2683,7 +2683,7 @@ b]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen remains unmodified
   screen-should-contain [
@@ -2698,11 +2698,11 @@ scenario editor-starts-next-page-at-start-of-wrapped-line [
   # screen has 1 line for menu + 3 lines for text
   assume-screen 10/width, 4/height
   # editor contains a long last line
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 cdefgh]
   # editor screen triggers wrap of last line
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 4/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 4/right
   # some part of last line is not displayed
   screen-should-contain [
     .          .
@@ -2715,7 +2715,7 @@ cdefgh]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows entire wrapped line
   screen-should-contain [
@@ -2731,9 +2731,9 @@ scenario editor-starts-next-page-at-start-of-wrapped-line-2 [
   assume-screen 10/width, 4/height
   # editor contains a very long line that occupies last two lines of screen
   # and still has something left over
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 bcdefgh]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 4/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 4/right
   # some part of last line is not displayed
   screen-should-contain [
     .          .
@@ -2746,7 +2746,7 @@ bcdefgh]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows entire wrapped line
   screen-should-contain [
@@ -2761,11 +2761,11 @@ bcdefgh]
 
 scenario editor-can-scroll-up [
   assume-screen 10/width, 4/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   screen-should-contain [
     .          .
     .a         .
@@ -2777,7 +2777,7 @@ d]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows next page
   screen-should-contain [
@@ -2791,7 +2791,7 @@ d]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows original page again
   screen-should-contain [
@@ -2806,8 +2806,8 @@ after <handle-special-character> [
   {
     page-up?:boolean <- equal *c, 2/ctrl-b
     break-unless page-up?
-    top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
-    old-top:address:duplex-list:character <- copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
+    old-top:address:shared:duplex-list:character <- copy *top-of-screen
     <move-cursor-begin>
     editor <- page-up editor, screen-height
     undo-coalesce-tag:number <- copy 0/never
@@ -2822,8 +2822,8 @@ after <handle-special-key> [
   {
     page-up?:boolean <- equal *k, 65519/page-up
     break-unless page-up?
-    top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
-    old-top:address:duplex-list:character <- copy *top-of-screen
+    top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
+    old-top:address:shared:duplex-list:character <- copy *top-of-screen
     <move-cursor-begin>
     editor <- page-up editor, screen-height
     undo-coalesce-tag:number <- copy 0/never
@@ -2835,16 +2835,16 @@ after <handle-special-key> [
   }
 ]
 
-recipe page-up editor:address:editor-data, screen-height:number -> editor:address:editor-data [
+recipe page-up editor:address:shared:editor-data, screen-height:number -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
   max:number <- subtract screen-height, 1/menu-bar, 1/overlapping-line
   count:number <- copy 0
-  top-of-screen:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+  top-of-screen:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
   {
     done?:boolean <- greater-or-equal count, max
     break-if done?
-    prev:address:duplex-list:character <- before-previous-line *top-of-screen, editor
+    prev:address:shared:duplex-list:character <- before-previous-line *top-of-screen, editor
     break-unless prev
     *top-of-screen <- copy prev
     count <- add count, 1
@@ -2856,7 +2856,7 @@ scenario editor-can-scroll-up-multiple-pages [
   # screen has 1 line for menu + 3 lines
   assume-screen 10/width, 4/height
   # initialize editor with 8 lines
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
@@ -2864,7 +2864,7 @@ e
 f
 g
 h]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   screen-should-contain [
     .          .
     .a         .
@@ -2877,7 +2877,7 @@ h]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows third page
   screen-should-contain [
@@ -2891,7 +2891,7 @@ h]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows second page
   screen-should-contain [
@@ -2905,7 +2905,7 @@ h]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows original page again
   screen-should-contain [
@@ -2920,7 +2920,7 @@ scenario editor-can-scroll-up-wrapped-lines [
   # screen has 1 line for menu + 5 lines for text
   assume-screen 10/width, 6/height
   # editor contains a long line in the first page
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 cdefgh
 i
@@ -2931,7 +2931,7 @@ m
 n
 o]
   # editor screen triggers wrap of last line
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 4/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 4/right
   # some part of last line is not displayed
   screen-should-contain [
     .          .
@@ -2948,7 +2948,7 @@ o]
     press down-arrow
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows entire wrapped line
   screen-should-contain [
@@ -2964,7 +2964,7 @@ o]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen resets
   screen-should-contain [
@@ -2982,9 +2982,9 @@ scenario editor-can-scroll-up-wrapped-lines-2 [
   assume-screen 10/width, 4/height
   # editor contains a very long line that occupies last two lines of screen
   # and still has something left over
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 bcdefgh]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 4/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 4/right
   # some part of last line is not displayed
   screen-should-contain [
     .          .
@@ -2997,7 +2997,7 @@ bcdefgh]
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen shows entire wrapped line
   screen-should-contain [
@@ -3011,7 +3011,7 @@ bcdefgh]
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # screen resets
   screen-should-contain [
@@ -3025,7 +3025,7 @@ bcdefgh]
 scenario editor-can-scroll-up-past-nonempty-lines [
   assume-screen 10/width, 4/height
   # text with empty line in second screen
-  1:address:array:character <- new [axx
+  1:address:shared:array:character <- new [axx
 bxx
 cxx
 dxx
@@ -3034,7 +3034,7 @@ fxx
 gxx
 hxx
 ]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 4/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 4/right
   screen-should-contain [
     .          .
     .axx       .
@@ -3045,7 +3045,7 @@ hxx
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -3057,7 +3057,7 @@ hxx
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -3070,7 +3070,7 @@ hxx
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -3083,7 +3083,7 @@ hxx
 scenario editor-can-scroll-up-past-empty-lines [
   assume-screen 10/width, 4/height
   # text with empty line in second screen
-  1:address:array:character <- new [axy
+  1:address:shared:array:character <- new [axy
 bxy
 cxy
 
@@ -3092,7 +3092,7 @@ exy
 fxy
 gxy
 ]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 4/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 4/right
   screen-should-contain [
     .          .
     .axy       .
@@ -3103,7 +3103,7 @@ gxy
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -3115,7 +3115,7 @@ gxy
     press page-down
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -3128,7 +3128,7 @@ gxy
     press page-up
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
diff --git a/edit/004-programming-environment.mu b/edit/004-programming-environment.mu
index 7ed6376e..99cefbb4 100644
--- a/edit/004-programming-environment.mu
+++ b/edit/004-programming-environment.mu
@@ -6,22 +6,22 @@
 recipe! main [
   local-scope
   open-console
-  initial-recipe:address:array:character <- restore [recipes.mu]
-  initial-sandbox:address:array:character <- new []
+  initial-recipe:address:shared:array:character <- restore [recipes.mu]
+  initial-sandbox:address:shared:array:character <- new []
   hide-screen 0/screen
-  env:address:programming-environment-data <- new-programming-environment 0/screen, initial-recipe, initial-sandbox
+  env:address:shared:programming-environment-data <- new-programming-environment 0/screen, initial-recipe, initial-sandbox
   render-all 0/screen, env
   event-loop 0/screen, 0/console, env
   # never gets here
 ]
 
 container programming-environment-data [
-  recipes:address:editor-data
-  current-sandbox:address:editor-data
+  recipes:address:shared:editor-data
+  current-sandbox:address:shared:editor-data
   sandbox-in-focus?:boolean  # false => cursor in recipes; true => cursor in current-sandbox
 ]
 
-recipe new-programming-environment screen:address:screen, initial-recipe-contents:address:array:character, initial-sandbox-contents:address:array:character -> result:address:programming-environment-data, screen:address:screen [
+recipe new-programming-environment screen:address:shared:screen, initial-recipe-contents:address:shared:array:character, initial-sandbox-contents:address:shared:array:character -> result:address:shared:programming-environment-data, screen:address:shared:screen [
   local-scope
   load-ingredients
   width:number <- screen-width screen
@@ -33,25 +33,25 @@ recipe new-programming-environment screen:address:screen, initial-recipe-content
   button-on-screen?:boolean <- greater-or-equal button-start, 0
   assert button-on-screen?, [screen too narrow for menu]
   screen <- move-cursor screen, 0/row, button-start
-  run-button:address:array:character <- new [ run (F4) ]
+  run-button:address:shared:array:character <- new [ run (F4) ]
   print screen, run-button, 255/white, 161/reddish
   # dotted line down the middle
   divider:number, _ <- divide-with-remainder width, 2
   draw-vertical screen, divider, 1/top, height, 9482/vertical-dotted
   # recipe editor on the left
-  recipes:address:address:editor-data <- get-address *result, recipes:offset
+  recipes:address:address:shared:editor-data <- get-address *result, recipes:offset
   *recipes <- new-editor initial-recipe-contents, screen, 0/left, divider/right
   # sandbox editor on the right
   new-left:number <- add divider, 1
-  current-sandbox:address:address:editor-data <- get-address *result, current-sandbox:offset
+  current-sandbox:address:address:shared:editor-data <- get-address *result, current-sandbox:offset
   *current-sandbox <- new-editor initial-sandbox-contents, screen, new-left, width/right
 ]
 
-recipe event-loop screen:address:screen, console:address:console, env:address:programming-environment-data -> screen:address:screen, console:address:console, env:address:programming-environment-data [
+recipe event-loop screen:address:shared:screen, console:address:shared:console, env:address:shared:programming-environment-data -> screen:address:shared:screen, console:address:shared:console, env:address:shared:programming-environment-data [
   local-scope
   load-ingredients
-  recipes:address:editor-data <- get *env, recipes:offset
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  recipes:address:shared:editor-data <- get *env, recipes:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   sandbox-in-focus?:address:boolean <- get-address *env, sandbox-in-focus?:offset
   # if we fall behind we'll stop updating the screen, but then we have to
   # render the entire screen when we catch up.
@@ -179,14 +179,14 @@ recipe event-loop screen:address:screen, console:address:console, env:address:pr
   }
 ]
 
-recipe resize screen:address:screen, env:address:programming-environment-data -> env:address:programming-environment-data, screen:address:screen [
+recipe resize screen:address:shared:screen, env:address:shared:programming-environment-data -> env:address:shared:programming-environment-data, screen:address:shared:screen [
   local-scope
   load-ingredients
   clear-screen screen  # update screen dimensions
   width:number <- screen-width screen
   divider:number, _ <- divide-with-remainder width, 2
   # update recipe editor
-  recipes:address:editor-data <- get *env, recipes:offset
+  recipes:address:shared:editor-data <- get *env, recipes:offset
   right:address:number <- get-address *recipes, right:offset
   *right <- subtract divider, 1
   # reset cursor (later we'll try to preserve its position)
@@ -195,7 +195,7 @@ recipe resize screen:address:screen, env:address:programming-environment-data ->
   cursor-column:address:number <- get-address *recipes, cursor-column:offset
   *cursor-column <- copy 0
   # update sandbox editor
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   left:address:number <- get-address *current-sandbox, left:offset
   right:address:number <- get-address *current-sandbox, right:offset
   *left <- add divider, 1
@@ -211,9 +211,9 @@ scenario point-at-multiple-editors [
   trace-until 100/app  # trace too long
   assume-screen 30/width, 5/height
   # initialize both halves of screen
-  1:address:array:character <- new [abc]
-  2:address:array:character <- new [def]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:array:character <- new [def]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # focus on both sides
   assume-console [
     left-click 1, 1
@@ -221,11 +221,11 @@ scenario point-at-multiple-editors [
   ]
   # check cursor column in each
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
-    4:address:editor-data <- get *3:address:programming-environment-data, recipes:offset
-    5:number <- get *4:address:editor-data, cursor-column:offset
-    6:address:editor-data <- get *3:address:programming-environment-data, current-sandbox:offset
-    7:number <- get *6:address:editor-data, cursor-column:offset
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
+    4:address:shared:editor-data <- get *3:address:shared:programming-environment-data, recipes:offset
+    5:number <- get *4:address:shared:editor-data, cursor-column:offset
+    6:address:shared:editor-data <- get *3:address:shared:programming-environment-data, current-sandbox:offset
+    7:number <- get *6:address:shared:editor-data, cursor-column:offset
   ]
   memory-should-contain [
     5 <- 1
@@ -237,10 +237,10 @@ scenario edit-multiple-editors [
   trace-until 100/app  # trace too long
   assume-screen 30/width, 5/height
   # initialize both halves of screen
-  1:address:array:character <- new [abc]
-  2:address:array:character <- new [def]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  render-all screen, 3:address:programming-environment-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:array:character <- new [def]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  render-all screen, 3:address:shared:programming-environment-data
   # type one letter in each of them
   assume-console [
     left-click 1, 1
@@ -249,11 +249,11 @@ scenario edit-multiple-editors [
     type [1]
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
-    4:address:editor-data <- get *3:address:programming-environment-data, recipes:offset
-    5:number <- get *4:address:editor-data, cursor-column:offset
-    6:address:editor-data <- get *3:address:programming-environment-data, current-sandbox:offset
-    7:number <- get *6:address:editor-data, cursor-column:offset
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
+    4:address:shared:editor-data <- get *3:address:shared:programming-environment-data, recipes:offset
+    5:number <- get *4:address:shared:editor-data, cursor-column:offset
+    6:address:shared:editor-data <- get *3:address:shared:programming-environment-data, current-sandbox:offset
+    7:number <- get *6:address:shared:editor-data, cursor-column:offset
   ]
   screen-should-contain [
     .           run (F4)           .  # this line has a different background, but we don't test that yet
@@ -268,7 +268,7 @@ scenario edit-multiple-editors [
   # show the cursor at the right window
   run [
     8:character/cursor <- copy 9251/␣
-    print screen:address:screen, 8:character/cursor
+    print screen:address:shared:screen, 8:character/cursor
   ]
   screen-should-contain [
     .           run (F4)           .
@@ -282,10 +282,10 @@ scenario multiple-editors-cover-only-their-own-areas [
   trace-until 100/app  # trace too long
   assume-screen 60/width, 10/height
   run [
-    1:address:array:character <- new [abc]
-    2:address:array:character <- new [def]
-    3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-    render-all screen, 3:address:programming-environment-data
+    1:address:shared:array:character <- new [abc]
+    2:address:shared:array:character <- new [def]
+    3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+    render-all screen, 3:address:shared:programming-environment-data
   ]
   # divider isn't messed up
   screen-should-contain [
@@ -300,16 +300,16 @@ scenario multiple-editors-cover-only-their-own-areas [
 scenario editor-in-focus-keeps-cursor [
   trace-until 100/app  # trace too long
   assume-screen 30/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:array:character <- new [def]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  render-all screen, 3:address:programming-environment-data
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:array:character <- new [def]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  render-all screen, 3:address:shared:programming-environment-data
   # initialize programming environment and highlight cursor
   assume-console []
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
     4:character/cursor <- copy 9251/␣
-    print screen:address:screen, 4:character/cursor
+    print screen:address:shared:screen, 4:character/cursor
   ]
   # is cursor at the right place?
   screen-should-contain [
@@ -323,9 +323,9 @@ scenario editor-in-focus-keeps-cursor [
     type [z]
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
     4:character/cursor <- copy 9251/␣
-    print screen:address:screen, 4:character/cursor
+    print screen:address:shared:screen, 4:character/cursor
   ]
   # cursor should still be right
   screen-should-contain [
@@ -340,11 +340,11 @@ scenario backspace-in-sandbox-editor-joins-lines [
   trace-until 100/app  # trace too long
   assume-screen 30/width, 5/height
   # initialize sandbox side with two lines
-  1:address:array:character <- new []
-  2:address:array:character <- new [abc
+  1:address:shared:array:character <- new []
+  2:address:shared:array:character <- new [abc
 def]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  render-all screen, 3:address:programming-environment-data
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  render-all screen, 3:address:shared:programming-environment-data
   screen-should-contain [
     .           run (F4)           .
     .               ┊abc           .
@@ -358,9 +358,9 @@ def]
     press backspace
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
     4:character/cursor <- copy 9251/␣
-    print screen:address:screen, 4:character/cursor
+    print screen:address:shared:screen, 4:character/cursor
   ]
   # cursor moves to end of old line
   screen-should-contain [
@@ -371,7 +371,7 @@ def]
   ]
 ]
 
-recipe render-all screen:address:screen, env:address:programming-environment-data -> screen:address:screen [
+recipe render-all screen:address:shared:screen, env:address:shared:programming-environment-data -> screen:address:shared:screen [
   local-scope
   load-ingredients
   trace 10, [app], [render all]
@@ -384,7 +384,7 @@ recipe render-all screen:address:screen, env:address:programming-environment-dat
   button-on-screen?:boolean <- greater-or-equal button-start, 0
   assert button-on-screen?, [screen too narrow for menu]
   screen <- move-cursor screen, 0/row, button-start
-  run-button:address:array:character <- new [ run (F4) ]
+  run-button:address:shared:array:character <- new [ run (F4) ]
   print screen, run-button, 255/white, 161/reddish
   # dotted line down the middle
   trace 11, [app], [render divider]
@@ -396,19 +396,19 @@ recipe render-all screen:address:screen, env:address:programming-environment-dat
   screen <- render-sandbox-side screen, env
   <render-components-end>
   #
-  recipes:address:editor-data <- get *env, recipes:offset
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  recipes:address:shared:editor-data <- get *env, recipes:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   sandbox-in-focus?:boolean <- get *env, sandbox-in-focus?:offset
   screen <- update-cursor screen, recipes, current-sandbox, sandbox-in-focus?
   #
   show-screen screen
 ]
 
-recipe render-recipes screen:address:screen, env:address:programming-environment-data -> screen:address:screen [
+recipe render-recipes screen:address:shared:screen, env:address:shared:programming-environment-data -> screen:address:shared:screen [
   local-scope
   load-ingredients
   trace 11, [app], [render recipes]
-  recipes:address:editor-data <- get *env, recipes:offset
+  recipes:address:shared:editor-data <- get *env, recipes:offset
   # render recipes
   left:number <- get *recipes, left:offset
   right:number <- get *recipes, right:offset
@@ -423,10 +423,10 @@ recipe render-recipes screen:address:screen, env:address:programming-environment
 ]
 
 # replaced in a later layer
-recipe render-sandbox-side screen:address:screen, env:address:programming-environment-data -> screen:address:screen [
+recipe render-sandbox-side screen:address:shared:screen, env:address:shared:programming-environment-data -> screen:address:shared:screen [
   local-scope
   load-ingredients
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   left:number <- get *current-sandbox, left:offset
   right:number <- get *current-sandbox, right:offset
   row:number, column:number, screen, current-sandbox <- render screen, current-sandbox
@@ -438,7 +438,7 @@ recipe render-sandbox-side screen:address:screen, env:address:programming-enviro
   clear-screen-from screen, row, left, left, right
 ]
 
-recipe update-cursor screen:address:screen, recipes:address:editor-data, current-sandbox:address:editor-data, sandbox-in-focus?:boolean -> screen:address:screen [
+recipe update-cursor screen:address:shared:screen, recipes:address:shared:editor-data, current-sandbox:address:shared:editor-data, sandbox-in-focus?:boolean -> screen:address:shared:screen [
   local-scope
   load-ingredients
   {
@@ -456,7 +456,7 @@ recipe update-cursor screen:address:screen, recipes:address:editor-data, current
 
 # print a text 's' to 'editor' in 'color' starting at 'row'
 # clear rest of last line, move cursor to next line
-recipe render screen:address:screen, s:address:array:character, left:number, right:number, color:number, row:number -> row:number, screen:address:screen [
+recipe render screen:address:shared:screen, s:address:shared:array:character, left:number, right:number, color:number, row:number -> row:number, screen:address:shared:screen [
   local-scope
   load-ingredients
   reply-unless s
@@ -517,7 +517,7 @@ recipe render screen:address:screen, s:address:array:character, left:number, rig
 ]
 
 # like 'render' for texts, but with colorization for comments like in the editor
-recipe render-code screen:address:screen, s:address:array:character, left:number, right:number, row:number -> row:number, screen:address:screen [
+recipe render-code screen:address:shared:screen, s:address:shared:array:character, left:number, right:number, row:number -> row:number, screen:address:shared:screen [
   local-scope
   load-ingredients
   reply-unless s
@@ -585,7 +585,7 @@ after <global-type> [
   {
     redraw-screen?:boolean <- equal *c, 12/ctrl-l
     break-unless redraw-screen?
-    screen <- render-all screen, env:address:programming-environment-data
+    screen <- render-all screen, env:address:shared:programming-environment-data
     sync-screen screen
     loop +next-event:label
   }
@@ -606,7 +606,7 @@ after <global-type> [
 
 ## helpers
 
-recipe draw-vertical screen:address:screen, col:number, y:number, bottom:number -> screen:address:screen [
+recipe draw-vertical screen:address:shared:screen, col:number, y:number, bottom:number -> screen:address:shared:screen [
   local-scope
   load-ingredients
   style:character, style-found?:boolean <- next-ingredient
diff --git a/edit/005-sandbox.mu b/edit/005-sandbox.mu
index 3929fb76..3095e865 100644
--- a/edit/005-sandbox.mu
+++ b/edit/005-sandbox.mu
@@ -7,10 +7,10 @@
 recipe! main [
   local-scope
   open-console
-  initial-recipe:address:array:character <- restore [recipes.mu]
-  initial-sandbox:address:array:character <- new []
+  initial-recipe:address:shared:array:character <- restore [recipes.mu]
+  initial-sandbox:address:shared:array:character <- new []
   hide-screen 0/screen
-  env:address:programming-environment-data <- new-programming-environment 0/screen, initial-recipe, initial-sandbox
+  env:address:shared:programming-environment-data <- new-programming-environment 0/screen, initial-recipe, initial-sandbox
   env <- restore-sandboxes env
   render-all 0/screen, env
   event-loop 0/screen, 0/console, env
@@ -18,35 +18,35 @@ recipe! main [
 ]
 
 container programming-environment-data [
-  sandbox:address:sandbox-data  # list of sandboxes, from top to bottom
+  sandbox:address:shared:sandbox-data  # list of sandboxes, from top to bottom
 ]
 
 container sandbox-data [
-  data:address:array:character
-  response:address:array:character
-  expected-response:address:array:character
+  data:address:shared:array:character
+  response:address:shared:array:character
+  expected-response:address:shared:array:character
   # coordinates to track clicks
   starting-row-on-screen:number
   code-ending-row-on-screen:number  # past end of code
   response-starting-row-on-screen:number
-  screen:address:screen  # prints in the sandbox go here
-  next-sandbox:address:sandbox-data
+  screen:address:shared:screen  # prints in the sandbox go here
+  next-sandbox:address:shared:sandbox-data
 ]
 
 scenario run-and-show-results [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
   # recipe editor is empty
-  1:address:array:character <- new []
+  1:address:shared:array:character <- new []
   # sandbox editor contains an instruction without storing outputs
-  2:address:array:character <- new [divide-with-remainder 11, 3]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [divide-with-remainder 11, 3]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the code in the editors
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # check that screen prints the results
   screen-should-contain [
@@ -89,7 +89,7 @@ scenario run-and-show-results [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # check that screen prints the results
   screen-should-contain [
@@ -115,14 +115,14 @@ after <global-keypress> [
     do-run?:boolean <- equal *k, 65532/F4
     break-unless do-run?
 #?     $log [F4 pressed]
-    status:address:array:character <- new [running...  ]
+    status:address:shared:array:character <- new [running...  ]
     screen <- update-status screen, status, 245/grey
     error?:boolean, env, screen <- run-sandboxes env, screen
     # F4 might update warnings and results on both sides
     screen <- render-all screen, env
     {
       break-if error?
-      status:address:array:character <- new [            ]
+      status:address:shared:array:character <- new [            ]
       screen <- update-status screen, status, 245/grey
     }
     screen <- update-cursor screen, recipes, current-sandbox, *sandbox-in-focus?
@@ -130,36 +130,36 @@ after <global-keypress> [
   }
 ]
 
-recipe run-sandboxes env:address:programming-environment-data, screen:address:screen -> errors-found?:boolean, env:address:programming-environment-data, screen:address:screen [
+recipe run-sandboxes env:address:shared:programming-environment-data, screen:address:shared:screen -> errors-found?:boolean, env:address:shared:programming-environment-data, screen:address:shared:screen [
   local-scope
   load-ingredients
   errors-found?:boolean, env, screen <- update-recipes env, screen
   reply-if errors-found?
   # check contents of right editor (sandbox)
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   {
-    sandbox-contents:address:array:character <- editor-contents current-sandbox
+    sandbox-contents:address:shared:array:character <- editor-contents current-sandbox
     break-unless sandbox-contents
     # if contents exist, first save them
     # run them and turn them into a new sandbox-data
-    new-sandbox:address:sandbox-data <- new sandbox-data:type
-    data:address:address:array:character <- get-address *new-sandbox, data:offset
+    new-sandbox:address:shared:sandbox-data <- new sandbox-data:type
+    data:address:address:shared:array:character <- get-address *new-sandbox, data:offset
     *data <- copy sandbox-contents
     # push to head of sandbox list
-    dest:address:address:sandbox-data <- get-address *env, sandbox:offset
-    next:address:address:sandbox-data <- get-address *new-sandbox, next-sandbox:offset
+    dest:address:address:shared:sandbox-data <- get-address *env, sandbox:offset
+    next:address:address:shared:sandbox-data <- get-address *new-sandbox, next-sandbox:offset
     *next <- copy *dest
     *dest <- copy new-sandbox
     # clear sandbox editor
-    init:address:address:duplex-list:character <- get-address *current-sandbox, data:offset
+    init:address:address:shared:duplex-list:character <- get-address *current-sandbox, data:offset
     *init <- push 167/§, 0/tail
-    top-of-screen:address:address:duplex-list:character <- get-address *current-sandbox, top-of-screen:offset
+    top-of-screen:address:address:shared:duplex-list:character <- get-address *current-sandbox, top-of-screen:offset
     *top-of-screen <- copy *init
   }
   # save all sandboxes before running, just in case we die when running
   save-sandboxes env
   # run all sandboxes
-  curr:address:sandbox-data <- get *env, sandbox:offset
+  curr:address:shared:sandbox-data <- get *env, sandbox:offset
   {
     break-unless curr
     curr <- update-sandbox curr
@@ -171,49 +171,49 @@ recipe run-sandboxes env:address:programming-environment-data, screen:address:sc
 
 # copy code from recipe editor, persist, load into mu
 # replaced in a later layer (whereupon errors-found? will actually be set)
-recipe update-recipes env:address:programming-environment-data, screen:address:screen -> errors-found?:boolean, env:address:programming-environment-data, screen:address:screen [
+recipe update-recipes env:address:shared:programming-environment-data, screen:address:shared:screen -> errors-found?:boolean, env:address:shared:programming-environment-data, screen:address:shared:screen [
   local-scope
   load-ingredients
-  recipes:address:editor-data <- get *env, recipes:offset
-  in:address:array:character <- editor-contents recipes
+  recipes:address:shared:editor-data <- get *env, recipes:offset
+  in:address:shared:array:character <- editor-contents recipes
   save [recipes.mu], in  # newlayer: persistence
   reload in
   errors-found? <- copy 0/false
 ]
 
 # replaced in a later layer
-recipe update-sandbox sandbox:address:sandbox-data -> sandbox:address:sandbox-data [
+recipe update-sandbox sandbox:address:shared:sandbox-data -> sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
-  data:address:array:character <- get *sandbox, data:offset
-  response:address:address:array:character <- get-address *sandbox, response:offset
-  fake-screen:address:address:screen <- get-address *sandbox, screen:offset
+  data:address:shared:array:character <- get *sandbox, data:offset
+  response:address:address:shared:array:character <- get-address *sandbox, response:offset
+  fake-screen:address:address:shared:screen <- get-address *sandbox, screen:offset
   *response, _, *fake-screen <- run-interactive data
 ]
 
-recipe update-status screen:address:screen, msg:address:array:character, color:number -> screen:address:screen [
+recipe update-status screen:address:shared:screen, msg:address:shared:array:character, color:number -> screen:address:shared:screen [
   local-scope
   load-ingredients
   screen <- move-cursor screen, 0, 2
   screen <- print screen, msg, color, 238/grey/background
 ]
 
-recipe save-sandboxes env:address:programming-environment-data [
+recipe save-sandboxes env:address:shared:programming-environment-data [
   local-scope
   load-ingredients
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   # first clear previous versions, in case we deleted some sandbox
   $system [rm lesson/[0-9]* >/dev/null 2>/dev/null]  # some shells can't handle '>&'
-  curr:address:sandbox-data <- get *env, sandbox:offset
-  suffix:address:array:character <- new [.out]
+  curr:address:shared:sandbox-data <- get *env, sandbox:offset
+  suffix:address:shared:array:character <- new [.out]
   idx:number <- copy 0
   {
     break-unless curr
-    data:address:array:character <- get *curr, data:offset
-    filename:address:array:character <- to-text idx
+    data:address:shared:array:character <- get *curr, data:offset
+    filename:address:shared:array:character <- to-text idx
     save filename, data
     {
-      expected-response:address:array:character <- get *curr, expected-response:offset
+      expected-response:address:shared:array:character <- get *curr, expected-response:offset
       break-unless expected-response
       filename <- append filename, suffix
       save filename, expected-response
@@ -224,24 +224,24 @@ recipe save-sandboxes env:address:programming-environment-data [
   }
 ]
 
-recipe! render-sandbox-side screen:address:screen, env:address:programming-environment-data -> screen:address:screen [
+recipe! render-sandbox-side screen:address:shared:screen, env:address:shared:programming-environment-data -> screen:address:shared:screen [
   local-scope
   load-ingredients
 #?   $log [render sandbox side]
   trace 11, [app], [render sandbox side]
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   left:number <- get *current-sandbox, left:offset
   right:number <- get *current-sandbox, right:offset
   row:number, column:number, screen, current-sandbox <- render screen, current-sandbox
   clear-screen-from screen, row, column, left, right
   row <- add row, 1
   draw-horizontal screen, row, left, right, 9473/horizontal-double
-  sandbox:address:sandbox-data <- get *env, sandbox:offset
+  sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
   row, screen <- render-sandboxes screen, sandbox, left, right, row
   clear-rest-of-screen screen, row, left, left, right
 ]
 
-recipe render-sandboxes screen:address:screen, sandbox:address:sandbox-data, left:number, right:number, row:number -> row:number, screen:address:screen, sandbox:address:sandbox-data [
+recipe render-sandboxes screen:address:shared:screen, sandbox:address:shared:sandbox-data, left:number, right:number, row:number -> row:number, screen:address:shared:screen, sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
 #?   $log [render sandbox]
@@ -261,16 +261,16 @@ recipe render-sandboxes screen:address:screen, sandbox:address:sandbox-data, lef
   # render sandbox contents
   row <- add row, 1
   screen <- move-cursor screen, row, left
-  sandbox-data:address:array:character <- get *sandbox, data:offset
+  sandbox-data:address:shared:array:character <- get *sandbox, data:offset
   row, screen <- render-code screen, sandbox-data, left, right, row
   code-ending-row:address:number <- get-address *sandbox, code-ending-row-on-screen:offset
   *code-ending-row <- copy row
   # render sandbox warnings, screen or response, in that order
   response-starting-row:address:number <- get-address *sandbox, response-starting-row-on-screen:offset
-  sandbox-response:address:array:character <- get *sandbox, response:offset
+  sandbox-response:address:shared:array:character <- get *sandbox, response:offset
   <render-sandbox-results>
   {
-    sandbox-screen:address:screen <- get *sandbox, screen:offset
+    sandbox-screen:address:shared:screen <- get *sandbox, screen:offset
     empty-screen?:boolean <- fake-screen-is-empty? sandbox-screen
     break-if empty-screen?
     row, screen <- render-screen screen, sandbox-screen, left, right, row
@@ -287,32 +287,32 @@ recipe render-sandboxes screen:address:screen, sandbox:address:sandbox-data, lef
   # draw solid line after sandbox
   draw-horizontal screen, row, left, right, 9473/horizontal-double
   # draw next sandbox
-  next-sandbox:address:sandbox-data <- get *sandbox, next-sandbox:offset
+  next-sandbox:address:shared:sandbox-data <- get *sandbox, next-sandbox:offset
   row, screen <- render-sandboxes screen, next-sandbox, left, right, row
 ]
 
 # assumes programming environment has no sandboxes; restores them from previous session
-recipe restore-sandboxes env:address:programming-environment-data -> env:address:programming-environment-data [
+recipe restore-sandboxes env:address:shared:programming-environment-data -> env:address:shared:programming-environment-data [
   local-scope
   load-ingredients
   # read all scenarios, pushing them to end of a list of scenarios
-  suffix:address:array:character <- new [.out]
+  suffix:address:shared:array:character <- new [.out]
   idx:number <- copy 0
-  curr:address:address:sandbox-data <- get-address *env, sandbox:offset
+  curr:address:address:shared:sandbox-data <- get-address *env, sandbox:offset
   {
-    filename:address:array:character <- to-text idx
-    contents:address:array:character <- restore filename
+    filename:address:shared:array:character <- to-text idx
+    contents:address:shared:array:character <- restore filename
     break-unless contents  # stop at first error; assuming file didn't exist
     # create new sandbox for file
     *curr <- new sandbox-data:type
-    data:address:address:array:character <- get-address **curr, data:offset
+    data:address:address:shared:array:character <- get-address **curr, data:offset
     *data <- copy contents
     # restore expected output for sandbox if it exists
     {
       filename <- append filename, suffix
       contents <- restore filename
       break-unless contents
-      expected-response:address:address:array:character <- get-address **curr, expected-response:offset
+      expected-response:address:address:shared:array:character <- get-address **curr, expected-response:offset
       *expected-response <- copy contents
     }
     +continue
@@ -324,19 +324,19 @@ recipe restore-sandboxes env:address:programming-environment-data -> env:address
 
 # print the fake sandbox screen to 'screen' with appropriate delimiters
 # leave cursor at start of next line
-recipe render-screen screen:address:screen, sandbox-screen:address:screen, left:number, right:number, row:number -> row:number, screen:address:screen [
+recipe render-screen screen:address:shared:screen, sandbox-screen:address:shared:screen, left:number, right:number, row:number -> row:number, screen:address:shared:screen [
   local-scope
   load-ingredients
   reply-unless sandbox-screen
   # print 'screen:'
-  header:address:array:character <- new [screen:]
+  header:address:shared:array:character <- new [screen:]
   row <- render screen, header, left, right, 245/grey, row
   screen <- move-cursor screen, row, left
   # start printing sandbox-screen
   column:number <- copy left
   s-width:number <- screen-width sandbox-screen
   s-height:number <- screen-height sandbox-screen
-  buf:address:array:screen-cell <- get *sandbox-screen, data:offset
+  buf:address:shared:array:screen-cell <- get *sandbox-screen, data:offset
   stop-printing:number <- add left, s-width, 3
   max-column:number <- min stop-printing, right
   i:number <- copy 0
@@ -394,19 +394,19 @@ scenario run-updates-results [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 12/height
   # define a recipe (no indent for the 'add' line below so column numbers are more obvious)
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
 z:number <- add 2, 2
 reply z
 ]]
   # sandbox editor contains an instruction without storing outputs
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the code in the editors
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                                                                                 run (F4)           .
     .                                                  ┊                                                 .
@@ -425,7 +425,7 @@ reply z
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # check that screen updates the result on the right
   screen-should-contain [
@@ -444,16 +444,16 @@ scenario run-instruction-manages-screen-per-sandbox [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 20/height
   # left editor is empty
-  1:address:array:character <- new []
+  1:address:shared:array:character <- new []
   # right editor contains an instruction
-  2:address:array:character <- new [print-integer screen, 4]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [print-integer screen, 4]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the code in the editor
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # check that it prints a little toy screen
   screen-should-contain [
@@ -473,11 +473,11 @@ scenario run-instruction-manages-screen-per-sandbox [
   ]
 ]
 
-recipe editor-contents editor:address:editor-data -> result:address:array:character [
+recipe editor-contents editor:address:shared:editor-data -> result:address:shared:array:character [
   local-scope
   load-ingredients
-  buf:address:buffer <- new-buffer 80
-  curr:address:duplex-list:character <- get *editor, data:offset
+  buf:address:shared:buffer <- new-buffer 80
+  curr:address:shared:duplex-list:character <- get *editor, data:offset
   # skip § sentinel
   assert curr, [editor without data is illegal; must have at least a sentinel]
   curr <- next curr
@@ -494,16 +494,16 @@ recipe editor-contents editor:address:editor-data -> result:address:array:charac
 
 scenario editor-provides-edited-contents [
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
+  1:address:shared:array:character <- new [abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
   assume-console [
     left-click 1, 2
     type [def]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:address:array:character <- editor-contents 2:address:editor-data
-    4:array:character <- copy *3:address:array:character
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:address:shared:array:character <- editor-contents 2:address:shared:editor-data
+    4:array:character <- copy *3:address:shared:array:character
   ]
   memory-should-contain [
     4:array:character <- [abdefc]
diff --git a/edit/006-sandbox-edit.mu b/edit/006-sandbox-edit.mu
index 0e294be3..80ceb2b9 100644
--- a/edit/006-sandbox-edit.mu
+++ b/edit/006-sandbox-edit.mu
@@ -4,17 +4,17 @@ scenario clicking-on-a-sandbox-moves-it-to-editor [
   trace-until 100/app  # trace too long
   assume-screen 40/width, 10/height
   # basic recipe
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   reply 4
 ]]
   # run it
-  2:address:array:character <- new [foo]
+  2:address:shared:array:character <- new [foo]
   assume-console [
     press F4
   ]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                     run (F4)           .
     .                    ┊                   .
@@ -30,7 +30,7 @@ recipe foo [
     left-click 3, 30
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # it pops back into editor
   screen-should-contain [
@@ -48,7 +48,7 @@ recipe foo [
     type [0]
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                     run (F4)           .
@@ -69,7 +69,7 @@ after <global-touch> [
     click-column:number <- get *t, column:offset
     on-sandbox-side?:boolean <- greater-or-equal click-column, sandbox-left-margin
     break-unless on-sandbox-side?
-    first-sandbox:address:sandbox-data <- get *env, sandbox:offset
+    first-sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
     break-unless first-sandbox
     first-sandbox-begins:number <- get *first-sandbox, starting-row-on-screen:offset
     click-row:number <- get *t, row:offset
@@ -78,8 +78,8 @@ after <global-touch> [
     empty-sandbox-editor?:boolean <- empty-editor? current-sandbox
     break-unless empty-sandbox-editor?  # don't clobber existing contents
     # identify the sandbox to edit and remove it from the sandbox list
-    sandbox:address:sandbox-data <- extract-sandbox env, click-row
-    text:address:array:character <- get *sandbox, data:offset
+    sandbox:address:shared:sandbox-data <- extract-sandbox env, click-row
+    text:address:shared:array:character <- get *sandbox, data:offset
     current-sandbox <- insert-text current-sandbox, text
     hide-screen screen
     screen <- render-sandbox-side screen, env
@@ -89,24 +89,24 @@ after <global-touch> [
   }
 ]
 
-recipe empty-editor? editor:address:editor-data -> result:boolean [
+recipe empty-editor? editor:address:shared:editor-data -> result:boolean [
   local-scope
   load-ingredients
-  head:address:duplex-list:character <- get *editor, data:offset
-  first:address:duplex-list:character <- next head
+  head:address:shared:duplex-list:character <- get *editor, data:offset
+  first:address:shared:duplex-list:character <- next head
   result <- not first
 ]
 
-recipe extract-sandbox env:address:programming-environment-data, click-row:number -> result:address:sandbox-data, env:address:programming-environment-data [
+recipe extract-sandbox env:address:shared:programming-environment-data, click-row:number -> result:address:shared:sandbox-data, env:address:shared:programming-environment-data [
   local-scope
   load-ingredients
   # assert click-row >= sandbox.starting-row-on-screen
-  sandbox:address:address:sandbox-data <- get-address *env, sandbox:offset
+  sandbox:address:address:shared:sandbox-data <- get-address *env, sandbox:offset
   start:number <- get **sandbox, starting-row-on-screen:offset
   clicked-on-sandboxes?:boolean <- greater-or-equal click-row, start
   assert clicked-on-sandboxes?, [extract-sandbox called on click to sandbox editor]
   {
-    next-sandbox:address:sandbox-data <- get **sandbox, next-sandbox:offset
+    next-sandbox:address:shared:sandbox-data <- get **sandbox, next-sandbox:offset
     break-unless next-sandbox
     # if click-row < sandbox.next-sandbox.starting-row-on-screen, break
     next-start:number <- get *next-sandbox, starting-row-on-screen:offset
@@ -127,15 +127,15 @@ scenario sandbox-with-print-can-be-edited [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 20/height
   # left editor is empty
-  1:address:array:character <- new []
+  1:address:shared:array:character <- new []
   # right editor contains an instruction
-  2:address:array:character <- new [print-integer screen, 4]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [print-integer screen, 4]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the sandbox
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                                                                                 run (F4)           .
     .                                                  ┊                                                 .
@@ -156,7 +156,7 @@ scenario sandbox-with-print-can-be-edited [
     left-click 3, 70
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                                                                                 run (F4)           .
diff --git a/edit/007-sandbox-delete.mu b/edit/007-sandbox-delete.mu
index e9d28ffa..95b6042f 100644
--- a/edit/007-sandbox-delete.mu
+++ b/edit/007-sandbox-delete.mu
@@ -3,9 +3,9 @@
 scenario deleting-sandboxes [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
-  1:address:array:character <- new []
-  2:address:array:character <- new []
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  1:address:shared:array:character <- new []
+  2:address:shared:array:character <- new []
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run a few commands
   assume-console [
     left-click 1, 80
@@ -14,7 +14,7 @@ scenario deleting-sandboxes [
     type [add 2, 2]
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                                                                                 run (F4)           .
     .                                                  ┊                                                 .
@@ -35,7 +35,7 @@ scenario deleting-sandboxes [
     left-click 7, 99
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                                                                                 run (F4)           .
@@ -53,7 +53,7 @@ scenario deleting-sandboxes [
     left-click 3, 99
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                                                                                 run (F4)           .
@@ -77,17 +77,17 @@ after <global-touch> [
   }
 ]
 
-recipe delete-sandbox t:touch-event, env:address:programming-environment-data -> was-delete?:boolean, env:address:programming-environment-data [
+recipe delete-sandbox t:touch-event, env:address:shared:programming-environment-data -> was-delete?:boolean, env:address:shared:programming-environment-data [
   local-scope
   load-ingredients
   click-column:number <- get t, column:offset
-  current-sandbox:address:editor-data <- get *env, current-sandbox:offset
+  current-sandbox:address:shared:editor-data <- get *env, current-sandbox:offset
   right:number <- get *current-sandbox, right:offset
   at-right?:boolean <- equal click-column, right
   reply-unless at-right?, 0/false
   click-row:number <- get t, row:offset
-  prev:address:address:sandbox-data <- get-address *env, sandbox:offset
-  curr:address:sandbox-data <- get *env, sandbox:offset
+  prev:address:address:shared:sandbox-data <- get-address *env, sandbox:offset
+  curr:address:shared:sandbox-data <- get *env, sandbox:offset
   {
     break-unless curr
     # more sandboxes to check
diff --git a/edit/008-sandbox-test.mu b/edit/008-sandbox-test.mu
index 77cac2ce..b15eb37e 100644
--- a/edit/008-sandbox-test.mu
+++ b/edit/008-sandbox-test.mu
@@ -4,17 +4,17 @@ scenario sandbox-click-on-result-toggles-color-to-green [
   trace-until 100/app  # trace too long
   assume-screen 40/width, 10/height
   # basic recipe
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   reply 4
 ]]
   # run it
-  2:address:array:character <- new [foo]
+  2:address:shared:array:character <- new [foo]
   assume-console [
     press F4
   ]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                     run (F4)           .
     .                    ┊                   .
@@ -30,7 +30,7 @@ recipe foo [
     left-click 5, 21
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # color toggles to green
   screen-should-contain-in-color 2/green, [
@@ -46,7 +46,7 @@ recipe foo [
   # cursor should remain unmoved
   run [
     4:character/cursor <- copy 9251/␣
-    print screen:address:screen, 4:character/cursor
+    print screen:address:shared:screen, 4:character/cursor
   ]
   screen-should-contain [
     .                     run (F4)           .
@@ -67,7 +67,7 @@ recipe foo [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # result turns red
   screen-should-contain-in-color 1/red, [
@@ -90,14 +90,14 @@ after <global-touch> [
     click-column:number <- get *t, column:offset
     on-sandbox-side?:boolean <- greater-or-equal click-column, sandbox-left-margin
     break-unless on-sandbox-side?
-    first-sandbox:address:sandbox-data <- get *env, sandbox:offset
+    first-sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
     break-unless first-sandbox
     first-sandbox-begins:number <- get *first-sandbox, starting-row-on-screen:offset
     click-row:number <- get *t, row:offset
     below-sandbox-editor?:boolean <- greater-or-equal click-row, first-sandbox-begins
     break-unless below-sandbox-editor?
     # identify the sandbox whose output is being clicked on
-    sandbox:address:sandbox-data <- find-click-in-sandbox-output env, click-row
+    sandbox:address:shared:sandbox-data <- find-click-in-sandbox-output env, click-row
     break-unless sandbox
     # toggle its expected-response, and save session
     sandbox <- toggle-expected-response sandbox
@@ -111,17 +111,17 @@ after <global-touch> [
   }
 ]
 
-recipe find-click-in-sandbox-output env:address:programming-environment-data, click-row:number -> sandbox:address:sandbox-data [
+recipe find-click-in-sandbox-output env:address:shared:programming-environment-data, click-row:number -> sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
   # assert click-row >= sandbox.starting-row-on-screen
-  sandbox:address:sandbox-data <- get *env, sandbox:offset
+  sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
   start:number <- get *sandbox, starting-row-on-screen:offset
   clicked-on-sandboxes?:boolean <- greater-or-equal click-row, start
   assert clicked-on-sandboxes?, [extract-sandbox called on click to sandbox editor]
   # while click-row < sandbox.next-sandbox.starting-row-on-screen
   {
-    next-sandbox:address:sandbox-data <- get *sandbox, next-sandbox:offset
+    next-sandbox:address:shared:sandbox-data <- get *sandbox, next-sandbox:offset
     break-unless next-sandbox
     next-start:number <- get *next-sandbox, starting-row-on-screen:offset
     found?:boolean <- lesser-than click-row, next-start
@@ -137,10 +137,10 @@ recipe find-click-in-sandbox-output env:address:programming-environment-data, cl
   reply sandbox
 ]
 
-recipe toggle-expected-response sandbox:address:sandbox-data -> sandbox:address:sandbox-data [
+recipe toggle-expected-response sandbox:address:shared:sandbox-data -> sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
-  expected-response:address:address:array:character <- get-address *sandbox, expected-response:offset
+  expected-response:address:address:shared:array:character <- get-address *sandbox, expected-response:offset
   {
     # if expected-response is set, reset
     break-unless *expected-response
@@ -148,7 +148,7 @@ recipe toggle-expected-response sandbox:address:sandbox-data -> sandbox:address:
     reply sandbox/same-as-ingredient:0
   }
   # if not, current response is the expected response
-  response:address:array:character <- get *sandbox, response:offset
+  response:address:shared:array:character <- get *sandbox, response:offset
   *expected-response <- copy response
 ]
 
@@ -156,7 +156,7 @@ recipe toggle-expected-response sandbox:address:sandbox-data -> sandbox:address:
 after <render-sandbox-response> [
   {
     break-unless sandbox-response
-    expected-response:address:array:character <- get *sandbox, expected-response:offset
+    expected-response:address:shared:array:character <- get *sandbox, expected-response:offset
     break-unless expected-response  # fall-through to print in grey
     response-is-expected?:boolean <- equal expected-response, sandbox-response
     {
diff --git a/edit/009-sandbox-trace.mu b/edit/009-sandbox-trace.mu
index 03bde749..92d46bc0 100644
--- a/edit/009-sandbox-trace.mu
+++ b/edit/009-sandbox-trace.mu
@@ -4,17 +4,17 @@ scenario sandbox-click-on-code-toggles-app-trace [
   trace-until 100/app  # trace too long
   assume-screen 40/width, 10/height
   # basic recipe
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   stash [abc]
 ]]
   # run it
-  2:address:array:character <- new [foo]
+  2:address:shared:array:character <- new [foo]
   assume-console [
     press F4
   ]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                     run (F4)           .
     .                    ┊                   .
@@ -29,9 +29,9 @@ recipe foo [
     left-click 4, 21
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
     4:character/cursor-icon <- copy 9251/␣
-    print screen:address:screen, 4:character/cursor-icon
+    print screen:address:shared:screen, 4:character/cursor-icon
   ]
   # trace now printed and cursor shouldn't have budged
   screen-should-contain [
@@ -59,8 +59,8 @@ recipe foo [
     left-click 4, 25
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
-    print screen:address:screen, 4:character/cursor-icon
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
+    print screen:address:shared:screen, 4:character/cursor-icon
   ]
   # trace hidden again
   screen-should-contain [
@@ -78,18 +78,18 @@ scenario sandbox-shows-app-trace-and-result [
   trace-until 100/app  # trace too long
   assume-screen 40/width, 10/height
   # basic recipe
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   stash [abc]
   reply 4 
 ]]
   # run it
-  2:address:array:character <- new [foo]
+  2:address:shared:array:character <- new [foo]
   assume-console [
     press F4
   ]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   screen-should-contain [
     .                     run (F4)           .
     .                    ┊                   .
@@ -105,7 +105,7 @@ recipe foo [
     left-click 4, 21
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # trace now printed above result
   screen-should-contain [
@@ -122,18 +122,18 @@ recipe foo [
 ]
 
 container sandbox-data [
-  trace:address:array:character
+  trace:address:shared:array:character
   display-trace?:boolean
 ]
 
 # replaced in a later layer
-recipe! update-sandbox sandbox:address:sandbox-data -> sandbox:address:sandbox-data [
+recipe! update-sandbox sandbox:address:shared:sandbox-data -> sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
-  data:address:array:character <- get *sandbox, data:offset
-  response:address:address:array:character <- get-address *sandbox, response:offset
-  trace:address:address:array:character <- get-address *sandbox, trace:offset
-  fake-screen:address:address:screen <- get-address *sandbox, screen:offset
+  data:address:shared:array:character <- get *sandbox, data:offset
+  response:address:address:shared:array:character <- get-address *sandbox, response:offset
+  trace:address:address:shared:array:character <- get-address *sandbox, trace:offset
+  fake-screen:address:address:shared:screen <- get-address *sandbox, screen:offset
   *response, _, *fake-screen, *trace <- run-interactive data
 ]
 
@@ -145,14 +145,14 @@ after <global-touch> [
     click-column:number <- get *t, column:offset
     on-sandbox-side?:boolean <- greater-or-equal click-column, sandbox-left-margin
     break-unless on-sandbox-side?
-    first-sandbox:address:sandbox-data <- get *env, sandbox:offset
+    first-sandbox:address:shared:sandbox-data <- get *env, sandbox:offset
     break-unless first-sandbox
     first-sandbox-begins:number <- get *first-sandbox, starting-row-on-screen:offset
     click-row:number <- get *t, row:offset
     below-sandbox-editor?:boolean <- greater-or-equal click-row, first-sandbox-begins
     break-unless below-sandbox-editor?
     # identify the sandbox whose code is being clicked on
-    sandbox:address:sandbox-data <- find-click-in-sandbox-code env, click-row
+    sandbox:address:shared:sandbox-data <- find-click-in-sandbox-code env, click-row
     break-unless sandbox
     # toggle its display-trace? property
     x:address:boolean <- get-address *sandbox, display-trace?:offset
@@ -166,7 +166,7 @@ after <global-touch> [
   }
 ]
 
-recipe find-click-in-sandbox-code env:address:programming-environment-data, click-row:number -> sandbox:address:sandbox-data [
+recipe find-click-in-sandbox-code env:address:shared:programming-environment-data, click-row:number -> sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
   # assert click-row >= sandbox.starting-row-on-screen
@@ -176,7 +176,7 @@ recipe find-click-in-sandbox-code env:address:programming-environment-data, clic
   assert clicked-on-sandboxes?, [extract-sandbox called on click to sandbox editor]
   # while click-row < sandbox.next-sandbox.starting-row-on-screen
   {
-    next-sandbox:address:sandbox-data <- get *sandbox, next-sandbox:offset
+    next-sandbox:address:shared:sandbox-data <- get *sandbox, next-sandbox:offset
     break-unless next-sandbox
     next-start:number <- get *next-sandbox, starting-row-on-screen:offset
     found?:boolean <- lesser-than click-row, next-start
@@ -202,7 +202,7 @@ after <render-sandbox-results> [
   {
     display-trace?:boolean <- get *sandbox, display-trace?:offset
     break-unless display-trace?
-    sandbox-trace:address:array:character <- get *sandbox, trace:offset
+    sandbox-trace:address:shared:array:character <- get *sandbox, trace:offset
     break-unless sandbox-trace  # nothing to print; move on
     row, screen <- render screen, sandbox-trace, left, right, 245/grey, row
   }
diff --git a/edit/010-warnings.mu b/edit/010-warnings.mu
index 6bfa3e3e..61cac2d2 100644
--- a/edit/010-warnings.mu
+++ b/edit/010-warnings.mu
@@ -1,23 +1,23 @@
 ## handling malformed programs
 
 container programming-environment-data [
-  recipe-warnings:address:array:character
+  recipe-warnings:address:shared:array:character
 ]
 
 # copy code from recipe editor, persist, load into mu, save any warnings
-recipe! update-recipes env:address:programming-environment-data, screen:address:screen -> errors-found?:boolean, env:address:programming-environment-data, screen:address:screen [
+recipe! update-recipes env:address:shared:programming-environment-data, screen:address:shared:screen -> errors-found?:boolean, env:address:shared:programming-environment-data, screen:address:shared:screen [
   local-scope
   load-ingredients
 #?   $log [update recipes]
-  recipes:address:editor-data <- get *env, recipes:offset
-  in:address:array:character <- editor-contents recipes
+  recipes:address:shared:editor-data <- get *env, recipes:offset
+  in:address:shared:array:character <- editor-contents recipes
   save [recipes.mu], in
-  recipe-warnings:address:address:array:character <- get-address *env, recipe-warnings:offset
+  recipe-warnings:address:address:shared:array:character <- get-address *env, recipe-warnings:offset
   *recipe-warnings <- reload in
   # if recipe editor has errors, stop
   {
     break-unless *recipe-warnings
-    status:address:array:character <- new [errors found]
+    status:address:shared:array:character <- new [errors found]
     update-status screen, status, 1/red
     errors-found? <- copy 1/true
     reply
@@ -27,35 +27,35 @@ recipe! update-recipes env:address:programming-environment-data, screen:address:
 
 before <render-components-end> [
   trace 11, [app], [render status]
-  recipe-warnings:address:array:character <- get *env, recipe-warnings:offset
+  recipe-warnings:address:shared:array:character <- get *env, recipe-warnings:offset
   {
     break-unless recipe-warnings
-    status:address:array:character <- new [errors found]
+    status:address:shared:array:character <- new [errors found]
     update-status screen, status, 1/red
   }
 ]
 
 before <render-recipe-components-end> [
   {
-    recipe-warnings:address:array:character <- get *env, recipe-warnings:offset
+    recipe-warnings:address:shared:array:character <- get *env, recipe-warnings:offset
     break-unless recipe-warnings
     row, screen <- render screen, recipe-warnings, left, right, 1/red, row
   }
 ]
 
 container sandbox-data [
-  warnings:address:array:character
+  warnings:address:shared:array:character
 ]
 
-recipe! update-sandbox sandbox:address:sandbox-data -> sandbox:address:sandbox-data [
+recipe! update-sandbox sandbox:address:shared:sandbox-data -> sandbox:address:shared:sandbox-data [
   local-scope
   load-ingredients
 #?   $log [update sandbox]
-  data:address:array:character <- get *sandbox, data:offset
-  response:address:address:array:character <- get-address *sandbox, response:offset
-  warnings:address:address:array:character <- get-address *sandbox, warnings:offset
-  trace:address:address:array:character <- get-address *sandbox, trace:offset
-  fake-screen:address:address:screen <- get-address *sandbox, screen:offset
+  data:address:shared:array:character <- get *sandbox, data:offset
+  response:address:address:shared:array:character <- get-address *sandbox, response:offset
+  warnings:address:address:shared:array:character <- get-address *sandbox, warnings:offset
+  trace:address:address:shared:array:character <- get-address *sandbox, trace:offset
+  fake-screen:address:address:shared:screen <- get-address *sandbox, screen:offset
 #?   $print [run-interactive], 10/newline
   *response, *warnings, *fake-screen, *trace, completed?:boolean <- run-interactive data
   {
@@ -70,7 +70,7 @@ recipe! update-sandbox sandbox:address:sandbox-data -> sandbox:address:sandbox-d
 # make sure we render any trace
 after <render-sandbox-trace-done> [
   {
-    sandbox-warnings:address:array:character <- get *sandbox, warnings:offset
+    sandbox-warnings:address:shared:array:character <- get *sandbox, warnings:offset
     break-unless sandbox-warnings
     *response-starting-row <- copy 0  # no response
     row, screen <- render screen, sandbox-warnings, left, right, 1/red, row
@@ -82,17 +82,17 @@ after <render-sandbox-trace-done> [
 scenario run-shows-warnings-in-get [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   get 123:number, foo:offset
 ]]
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
@@ -122,14 +122,14 @@ recipe foo [
 scenario run-hides-warnings-from-past-sandboxes [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
-  1:address:array:character <- new []
-  2:address:array:character <- new [get foo, x:offset]  # invalid
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  1:address:shared:array:character <- new []
+  2:address:shared:array:character <- new [get foo, x:offset]  # invalid
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4  # generate error
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   assume-console [
     left-click 3, 80
@@ -138,7 +138,7 @@ scenario run-hides-warnings-from-past-sandboxes [
     press F4  # error should disappear
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                                                                                 run (F4)           .
@@ -156,18 +156,18 @@ scenario run-updates-warnings-for-shape-shifting-recipes [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
   # define a shape-shifting recipe with an error
-  1:address:array:character <- new [recipe foo x:_elem -> z:_elem [
+  1:address:shared:array:character <- new [recipe foo x:_elem -> z:_elem [
 local-scope
 load-ingredients
 z <- add x, [a]
 ]]
-  2:address:array:character <- new [foo 2]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo 2]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                                                                                 run (F4)           .
@@ -185,7 +185,7 @@ z <- add x, [a]
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # error should remain unchanged
   screen-should-contain [
@@ -205,24 +205,24 @@ scenario run-avoids-spurious-warnings-on-reloading-shape-shifting-recipes [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
   # overload a well-known shape-shifting recipe
-  1:address:array:character <- new [recipe length l:address:list:_elem -> n:number [
+  1:address:shared:array:character <- new [recipe length l:address:shared:list:_elem -> n:number [
 ]]
   # call code that uses other variants of it, but not it itself
-  2:address:array:character <- new [x:address:list:number <- copy 0
+  2:address:shared:array:character <- new [x:address:shared:list:number <- copy 0
 to-text x]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run it once
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   # no errors anywhere on screen (can't check anything else, since to-text will return an address)
   screen-should-contain-in-color 1/red, [
     .                                                                                                    .
     .                                                                                                    .
     .                                                                                                    .
     .                                                                                                    .
-    .                                                                         <-                         .
+    .                                                                                <-                  .
     .                                                                                                    .
     .                                                                                                    .
     .                                                                                                    .
@@ -239,7 +239,7 @@ to-text x]
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # still no errors
   screen-should-contain-in-color 1/red, [
@@ -247,7 +247,7 @@ to-text x]
     .                                                                                                    .
     .                                                                                                    .
     .                                                                                                    .
-    .                                                                         <-                         .
+    .                                                                                <-                  .
     .                                                                                                    .
     .                                                                                                    .
     .                                                                                                    .
@@ -264,17 +264,17 @@ to-text x]
 scenario run-shows-missing-type-warnings [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   x <- copy 0
 ]]
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
@@ -290,18 +290,18 @@ scenario run-shows-unbalanced-bracket-warnings [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
   # recipe is incomplete (unbalanced '[')
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo «
   x <- copy 0
 ]
-  replace 1:address:array:character, 171/«, 91  # '['
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  replace 1:address:shared:array:character, 171/«, 91  # '['
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
@@ -318,28 +318,28 @@ recipe foo «
 scenario run-shows-get-on-non-container-warnings [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
-  x:address:point <- new point:type
-  get x:address:point, 1:offset
+  x:address:shared:point <- new point:type
+  get x:address:shared:point, 1:offset
 ]]
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
     .                                                  ┊foo                                              .
     .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.
-    .  x:address:point <- new point:type               ┊                                                 .
-    .  get x:address:point, 1:offset                   ┊                                                 .
+    .  x:address:shared:point <- new point:type        ┊                                                 .
+    .  get x:address:shared:point, 1:offset            ┊                                                 .
     .]                                                 ┊                                                 .
     .foo: first ingredient of 'get' should be a contai↩┊                                                 .
-    .ner, but got x:address:point                      ┊                                                 .
+    .ner, but got x:address:shared:point               ┊                                                 .
     .┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┈┊                                                 .
     .                                                  ┊                                                 .
   ]
@@ -348,27 +348,27 @@ recipe foo [
 scenario run-shows-non-literal-get-argument-warnings [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 15/height
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   x:number <- copy 0
-  y:address:point <- new point:type
-  get *y:address:point, x:number
+  y:address:shared:point <- new point:type
+  get *y:address:shared:point, x:number
 ]]
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
     .                                                  ┊foo                                              .
     .recipe foo [                                      ┊━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━.
     .  x:number <- copy 0                              ┊                                                 .
-    .  y:address:point <- new point:type               ┊                                                 .
-    .  get *y:address:point, x:number                  ┊                                                 .
+    .  y:address:shared:point <- new point:type        ┊                                                 .
+    .  get *y:address:shared:point, x:number           ┊                                                 .
     .]                                                 ┊                                                 .
     .foo: expected ingredient 1 of 'get' to have type ↩┊                                                 .
     .'offset'; got x:number                            ┊                                                 .
@@ -383,17 +383,17 @@ scenario run-shows-warnings-everytime [
   trace-until 100/app  # trace too long
   # try to run a file with an error
   assume-screen 100/width, 15/height
-  1:address:array:character <- new [ 
+  1:address:shared:array:character <- new [ 
 recipe foo [
   x:number <- copy y:number
 ]]
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
@@ -410,7 +410,7 @@ recipe foo [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .  errors found                                                                   run (F4)           .
@@ -428,16 +428,16 @@ scenario run-instruction-and-print-warnings [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 10/height
   # left editor is empty
-  1:address:array:character <- new []
+  1:address:shared:array:character <- new []
   # right editor contains an illegal instruction
-  2:address:array:character <- new [get 1234:number, foo:offset]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [get 1234:number, foo:offset]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the code in the editors
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # check that screen prints error message in red
   screen-should-contain [
@@ -491,17 +491,17 @@ scenario run-instruction-and-print-warnings-only-once [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 10/height
   # left editor is empty
-  1:address:array:character <- new []
+  1:address:shared:array:character <- new []
   # right editor contains an illegal instruction
-  2:address:array:character <- new [get 1234:number, foo:offset]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [get 1234:number, foo:offset]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the code in the editors multiple times
   assume-console [
     press F4
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # check that screen prints error message just once
   screen-should-contain [
@@ -522,20 +522,20 @@ scenario sandbox-can-handle-infinite-loop [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 20/height
   # left editor is empty
-  1:address:array:character <- new [recipe foo [
+  1:address:shared:array:character <- new [recipe foo [
   {
     loop
   }
 ]]
   # right editor contains an instruction
-  2:address:array:character <- new [foo]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run the sandbox
   assume-console [
     press F4
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   screen-should-contain [
     .                                                                                 run (F4)           .
@@ -553,7 +553,7 @@ scenario sandbox-with-warnings-shows-trace [
   trace-until 100/app  # trace too long
   assume-screen 100/width, 10/height
   # generate a stash and a warning
-  1:address:array:character <- new [recipe foo [
+  1:address:shared:array:character <- new [recipe foo [
 local-scope
 a:number <- next-ingredient
 b:number <- next-ingredient
@@ -561,13 +561,13 @@ stash [dividing by], b
 _, c:number <- divide-with-remainder a, b
 reply b
 ]]
-  2:address:array:character <- new [foo 4, 0]
-  3:address:programming-environment-data <- new-programming-environment screen:address:screen, 1:address:array:character, 2:address:array:character
+  2:address:shared:array:character <- new [foo 4, 0]
+  3:address:shared:programming-environment-data <- new-programming-environment screen:address:shared:screen, 1:address:shared:array:character, 2:address:shared:array:character
   # run
   assume-console [
     press F4
   ]
-  event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+  event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   # screen prints error message
   screen-should-contain [
     .                                                                                 run (F4)           .
@@ -585,7 +585,7 @@ reply b
     left-click 4, 55
   ]
   run [
-    event-loop screen:address:screen, console:address:console, 3:address:programming-environment-data
+    event-loop screen:address:shared:screen, console:address:shared:console, 3:address:shared:programming-environment-data
   ]
   # screen should expand trace
   screen-should-contain [
diff --git a/edit/011-editor-undo.mu b/edit/011-editor-undo.mu
index 4939013e..82362dd9 100644
--- a/edit/011-editor-undo.mu
+++ b/edit/011-editor-undo.mu
@@ -11,13 +11,13 @@ exclusive-container operation [
 container insert-operation [
   before-row:number
   before-column:number
-  before-top-of-screen:address:duplex-list:character
+  before-top-of-screen:address:shared:duplex-list:character
   after-row:number
   after-column:number
-  after-top-of-screen:address:duplex-list:character
+  after-top-of-screen:address:shared:duplex-list:character
   # inserted text is from 'insert-from' until 'insert-until'; list doesn't have to terminate
-  insert-from:address:duplex-list:character
-  insert-until:address:duplex-list:character
+  insert-from:address:shared:duplex-list:character
+  insert-until:address:shared:duplex-list:character
   tag:number  # event causing this operation; might be used to coalesce runs of similar events
     # 0: no coalesce (enter+indent)
     # 1: regular alphanumeric characters
@@ -26,10 +26,10 @@ container insert-operation [
 container move-operation [
   before-row:number
   before-column:number
-  before-top-of-screen:address:duplex-list:character
+  before-top-of-screen:address:shared:duplex-list:character
   after-row:number
   after-column:number
-  after-top-of-screen:address:duplex-list:character
+  after-top-of-screen:address:shared:duplex-list:character
   tag:number  # event causing this operation; might be used to coalesce runs of similar events
     # 0: no coalesce (touch events, etc)
     # 1: left arrow
@@ -41,13 +41,13 @@ container move-operation [
 container delete-operation [
   before-row:number
   before-column:number
-  before-top-of-screen:address:duplex-list:character
+  before-top-of-screen:address:shared:duplex-list:character
   after-row:number
   after-column:number
-  after-top-of-screen:address:duplex-list:character
-  deleted-text:address:duplex-list:character
-  delete-from:address:duplex-list:character
-  delete-until:address:duplex-list:character
+  after-top-of-screen:address:shared:duplex-list:character
+  deleted-text:address:shared:duplex-list:character
+  delete-from:address:shared:duplex-list:character
+  delete-until:address:shared:duplex-list:character
   tag:number  # event causing this operation; might be used to coalesce runs of similar events
     # 0: no coalesce (ctrl-k, ctrl-u)
     # 1: backspace
@@ -56,8 +56,8 @@ container delete-operation [
 
 # every editor accumulates a list of operations to undo/redo
 container editor-data [
-  undo:address:list:address:operation
-  redo:address:list:address:operation
+  undo:address:shared:list:address:shared:operation
+  redo:address:shared:list:address:shared:operation
 ]
 
 # ctrl-z - undo operation
@@ -65,11 +65,11 @@ after <handle-special-character> [
   {
     undo?:boolean <- equal *c, 26/ctrl-z
     break-unless undo?
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
     break-unless *undo
-    op:address:operation <- first *undo
+    op:address:shared:operation <- first *undo
     *undo <- rest *undo
-    redo:address:address:list:address:operation <- get-address *editor, redo:offset
+    redo:address:address:shared:list:address:shared:operation <- get-address *editor, redo:offset
     *redo <- push op, *redo
     <handle-undo>
     reply screen/same-as-ingredient:0, editor/same-as-ingredient:1, 1/go-render
@@ -81,11 +81,11 @@ after <handle-special-character> [
   {
     redo?:boolean <- equal *c, 25/ctrl-y
     break-unless redo?
-    redo:address:address:list:address:operation <- get-address *editor, redo:offset
+    redo:address:address:shared:list:address:shared:operation <- get-address *editor, redo:offset
     break-unless *redo
-    op:address:operation <- first *redo
+    op:address:shared:operation <- first *redo
     *redo <- rest *redo
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
     *undo <- push op, *undo
     <handle-redo>
     reply screen/same-as-ingredient:0, editor/same-as-ingredient:1, 1/go-render
@@ -97,19 +97,19 @@ after <handle-special-character> [
 scenario editor-can-undo-typing [
   # create an editor and type a character
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [0]
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # character should be gone
   screen-should-contain [
@@ -123,7 +123,7 @@ scenario editor-can-undo-typing [
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -135,34 +135,34 @@ scenario editor-can-undo-typing [
 
 # save operation to undo
 after <insert-character-begin> [
-  top-before:address:duplex-list:character <- get *editor, top-of-screen:offset
-  cursor-before:address:duplex-list:character <- copy *before-cursor
+  top-before:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+  cursor-before:address:shared:duplex-list:character <- copy *before-cursor
 ]
 before <insert-character-end> [
-  top-after:address:duplex-list:character <- get *editor, top-of-screen:offset
-  undo:address:address:list:address:operation <- get-address *editor, undo:offset
+  top-after:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+  undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
   {
     # if previous operation was an insert, coalesce this operation with it
     break-unless *undo
-    op:address:operation <- first *undo
-    typing:address:insert-operation <- maybe-convert *op, typing:variant
+    op:address:shared:operation <- first *undo
+    typing:address:shared:insert-operation <- maybe-convert *op, typing:variant
     break-unless typing
     previous-coalesce-tag:number <- get *typing, tag:offset
     break-unless previous-coalesce-tag
-    insert-until:address:address:duplex-list:character <- get-address *typing, insert-until:offset
+    insert-until:address:address:shared:duplex-list:character <- get-address *typing, insert-until:offset
     *insert-until <- next *before-cursor
     after-row:address:number <- get-address *typing, after-row:offset
     *after-row <- copy *cursor-row
     after-column:address:number <- get-address *typing, after-column:offset
     *after-column <- copy *cursor-column
-    after-top:address:address:duplex-list:character <- get-address *typing, after-top-of-screen:offset
+    after-top:address:address:shared:duplex-list:character <- get-address *typing, after-top-of-screen:offset
     *after-top <- get *editor, top-of-screen:offset
     break +done-adding-insert-operation:label
   }
   # if not, create a new operation
-  insert-from:address:duplex-list:character <- next cursor-before
-  insert-to:address:duplex-list:character <- next insert-from
-  op:address:operation <- new operation:type
+  insert-from:address:shared:duplex-list:character <- next cursor-before
+  insert-to:address:shared:duplex-list:character <- next insert-from
+  op:address:shared:operation <- new operation:type
   *op <- merge 0/insert-operation, save-row/before, save-column/before, top-before, *cursor-row/after, *cursor-column/after, top-after, insert-from, insert-to, 1/coalesce
   editor <- add-operation editor, op
   +done-adding-insert-operation
@@ -172,15 +172,15 @@ before <insert-character-end> [
 after <insert-enter-begin> [
   cursor-row-before:number <- copy *cursor-row
   cursor-column-before:number <- copy *cursor-column
-  top-before:address:duplex-list:character <- get *editor, top-of-screen:offset
-  cursor-before:address:duplex-list:character <- copy *before-cursor
+  top-before:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+  cursor-before:address:shared:duplex-list:character <- copy *before-cursor
 ]
 before <insert-enter-end> [
-  top-after:address:duplex-list:character <- get *editor, top-of-screen:offset
+  top-after:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
   # never coalesce
-  insert-from:address:duplex-list:character <- next cursor-before
-  insert-to:address:duplex-list:character <- next *before-cursor
-  op:address:operation <- new operation:type
+  insert-from:address:shared:duplex-list:character <- next cursor-before
+  insert-to:address:shared:duplex-list:character <- next *before-cursor
+  op:address:shared:operation <- new operation:type
   *op <- merge 0/insert-operation, cursor-row-before, cursor-column-before, top-before, *cursor-row/after, *cursor-column/after, top-after, insert-from, insert-to, 0/never-coalesce
   editor <- add-operation editor, op
 ]
@@ -189,28 +189,28 @@ before <insert-enter-end> [
 # redo stack, because it's now obsolete.
 # Beware: since we're counting cursor moves as operations, this means just
 # moving the cursor can lose work on the undo stack.
-recipe add-operation editor:address:editor-data, op:address:operation -> editor:address:editor-data [
+recipe add-operation editor:address:shared:editor-data, op:address:shared:operation -> editor:address:shared:editor-data [
   local-scope
   load-ingredients
-  undo:address:address:list:address:operation <- get-address *editor, undo:offset
+  undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
   *undo <- push op *undo
-  redo:address:address:list:address:operation <- get-address *editor, redo:offset
+  redo:address:address:shared:list:address:shared:operation <- get-address *editor, redo:offset
   *redo <- copy 0
   reply editor/same-as-ingredient:0
 ]
 
 after <handle-undo> [
   {
-    typing:address:insert-operation <- maybe-convert *op, typing:variant
+    typing:address:shared:insert-operation <- maybe-convert *op, typing:variant
     break-unless typing
-    start:address:duplex-list:character <- get *typing, insert-from:offset
-    end:address:duplex-list:character <- get *typing, insert-until:offset
+    start:address:shared:duplex-list:character <- get *typing, insert-from:offset
+    end:address:shared:duplex-list:character <- get *typing, insert-until:offset
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     *before-cursor <- prev start
     remove-between *before-cursor, end
     *cursor-row <- get *typing, before-row:offset
     *cursor-column <- get *typing, before-column:offset
-    top:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+    top:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
     *top <- get *typing, before-top-of-screen:offset
   }
 ]
@@ -218,19 +218,19 @@ after <handle-undo> [
 scenario editor-can-undo-typing-multiple [
   # create an editor and type multiple characters
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [012]
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # all characters must be gone
   screen-should-contain [
@@ -244,14 +244,14 @@ scenario editor-can-undo-typing-multiple [
 scenario editor-can-undo-typing-multiple-2 [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [a]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [a]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # type some characters
   assume-console [
     type [012]
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .012a      .
@@ -263,7 +263,7 @@ scenario editor-can-undo-typing-multiple-2 [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # back to original text
   screen-should-contain [
@@ -277,7 +277,7 @@ scenario editor-can-undo-typing-multiple-2 [
     type [3]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -290,15 +290,15 @@ scenario editor-can-undo-typing-multiple-2 [
 scenario editor-can-undo-typing-enter [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [  abc]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [  abc]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # new line
   assume-console [
     left-click 1, 8
     press enter
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .  abc     .
@@ -307,8 +307,8 @@ scenario editor-can-undo-typing-enter [
     .          .
   ]
   # line is indented
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 2
     4 <- 2
@@ -318,10 +318,10 @@ scenario editor-can-undo-typing-enter [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 5
@@ -338,7 +338,7 @@ scenario editor-can-undo-typing-enter [
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -353,14 +353,14 @@ scenario editor-can-undo-typing-enter [
 scenario editor-redo-typing [
   # create an editor, type something, undo
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [a]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new [a]
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [012]
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .a         .
@@ -372,7 +372,7 @@ scenario editor-redo-typing [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # all characters must be back
   screen-should-contain [
@@ -386,7 +386,7 @@ scenario editor-redo-typing [
     type [3]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -398,15 +398,15 @@ scenario editor-redo-typing [
 
 after <handle-redo> [
   {
-    typing:address:insert-operation <- maybe-convert *op, typing:variant
+    typing:address:shared:insert-operation <- maybe-convert *op, typing:variant
     break-unless typing
-    insert-from:address:duplex-list:character <- get *typing, insert-from:offset  # ignore insert-to because it's already been spliced away
+    insert-from:address:shared:duplex-list:character <- get *typing, insert-from:offset  # ignore insert-to because it's already been spliced away
     # assert insert-to matches next(*before-cursor)
     insert-range *before-cursor, insert-from
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     *cursor-row <- get *typing, after-row:offset
     *cursor-column <- get *typing, after-column:offset
-    top:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+    top:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
     *top <- get *typing, after-top-of-screen:offset
   }
 ]
@@ -414,14 +414,14 @@ after <handle-redo> [
 scenario editor-redo-typing-empty [
   # create an editor, type something, undo
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [012]
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .          .
@@ -433,7 +433,7 @@ scenario editor-redo-typing-empty [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # all characters must be back
   screen-should-contain [
@@ -447,7 +447,7 @@ scenario editor-redo-typing-empty [
     type [3]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -460,21 +460,21 @@ scenario editor-redo-typing-empty [
 scenario editor-work-clears-redo-stack [
   # create an editor with some text, do some work, undo
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [1]
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # do some more work
   assume-console [
     type [0]
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .0abc      .
@@ -487,7 +487,7 @@ ghi]
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # nothing should happen
   screen-should-contain [
@@ -502,9 +502,9 @@ ghi]
 scenario editor-can-redo-typing-and-enter-and-tab [
   # create an editor
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # insert some text and tabs, hit enter, some more text and tabs
   assume-console [
     press tab
@@ -515,7 +515,7 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press tab
     type [efg]
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .  ab  cd  .
@@ -523,8 +523,8 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 2
     4 <- 7
@@ -534,11 +534,11 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # typing in second line deleted, but not indent
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 2
     4 <- 2
@@ -555,11 +555,11 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # indent and newline deleted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 8
@@ -575,11 +575,11 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # empty screen
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 0
@@ -595,11 +595,11 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # first line inserted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 8
@@ -615,11 +615,11 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # newline and indent inserted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 2
     4 <- 2
@@ -636,11 +636,11 @@ scenario editor-can-redo-typing-and-enter-and-tab [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # indent and newline deleted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 2
     4 <- 7
@@ -659,24 +659,24 @@ scenario editor-can-redo-typing-and-enter-and-tab [
 scenario editor-can-undo-touch [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor
   assume-console [
     left-click 3, 1
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # click undone
   memory-should-contain [
@@ -688,7 +688,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -702,20 +702,20 @@ ghi]
 after <move-cursor-begin> [
   before-cursor-row:number <- get *editor, cursor-row:offset
   before-cursor-column:number <- get *editor, cursor-column:offset
-  before-top-of-screen:address:duplex-list:character <- get *editor, top-of-screen:offset
+  before-top-of-screen:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
 ]
 before <move-cursor-end> [
   after-cursor-row:number <- get *editor, cursor-row:offset
   after-cursor-column:number <- get *editor, cursor-column:offset
-  after-top-of-screen:address:duplex-list:character <- get *editor, top-of-screen:offset
+  after-top-of-screen:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
   {
     break-unless undo-coalesce-tag
     # if previous operation was also a move, and also had the same coalesce
     # tag, coalesce with it
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
     break-unless *undo
-    op:address:operation <- first *undo
-    move:address:move-operation <- maybe-convert *op, move:variant
+    op:address:shared:operation <- first *undo
+    move:address:shared:move-operation <- maybe-convert *op, move:variant
     break-unless move
     previous-coalesce-tag:number <- get *move, tag:offset
     coalesce?:boolean <- equal undo-coalesce-tag, previous-coalesce-tag
@@ -724,11 +724,11 @@ before <move-cursor-end> [
     *after-row <- copy after-cursor-row
     after-column:address:number <- get-address *move, after-column:offset
     *after-column <- copy after-cursor-column
-    after-top:address:address:duplex-list:character <- get-address *move, after-top-of-screen:offset
+    after-top:address:address:shared:duplex-list:character <- get-address *move, after-top-of-screen:offset
     *after-top <- get *editor, top-of-screen:offset
     break +done-adding-move-operation:label
   }
-  op:address:operation <- new operation:type
+  op:address:shared:operation <- new operation:type
   *op <- merge 1/move-operation, before-cursor-row, before-cursor-column, before-top-of-screen, after-cursor-row, after-cursor-column, after-top-of-screen, undo-coalesce-tag
   editor <- add-operation editor, op
   +done-adding-move-operation
@@ -736,10 +736,10 @@ before <move-cursor-end> [
 
 after <handle-undo> [
   {
-    move:address:move-operation <- maybe-convert *op, move:variant
+    move:address:shared:move-operation <- maybe-convert *op, move:variant
     break-unless move
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
-    top:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+    top:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
     *cursor-row <- get *move, before-row:offset
     *cursor-column <- get *move, before-column:offset
     *top <- get *move, before-top-of-screen:offset
@@ -750,18 +750,18 @@ scenario editor-can-undo-scroll [
   # screen has 1 line for menu + 3 lines
   assume-screen 5/width, 4/height
   # editor contains a wrapped line
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 cdefgh]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 5/right
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 5/right
   # position cursor at end of screen and try to move right
   assume-console [
     left-click 3, 3
     press right-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   # screen scrolls
   screen-should-contain [
     .     .
@@ -778,9 +778,9 @@ cdefgh]
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moved back
   memory-should-contain [
@@ -799,7 +799,7 @@ cdefgh]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .     .
@@ -812,25 +812,25 @@ cdefgh]
 scenario editor-can-undo-left-arrow [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor
   assume-console [
     left-click 3, 1
     press left-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -842,7 +842,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -856,19 +856,19 @@ ghi]
 scenario editor-can-undo-up-arrow [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor
   assume-console [
     left-click 3, 1
     press up-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 2
     4 <- 1
@@ -878,9 +878,9 @@ ghi]
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -892,7 +892,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -906,25 +906,25 @@ ghi]
 scenario editor-can-undo-down-arrow [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor
   assume-console [
     left-click 2, 1
     press down-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -936,7 +936,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -950,27 +950,27 @@ ghi]
 scenario editor-can-undo-ctrl-f [
   # create an editor with multiple pages of text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
 e
 f]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # scroll the page
   assume-console [
     press ctrl-f
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen should again show page 1
   screen-should-contain [
@@ -985,27 +985,27 @@ f]
 scenario editor-can-undo-page-down [
   # create an editor with multiple pages of text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
 e
 f]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # scroll the page
   assume-console [
     press page-down
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen should again show page 1
   screen-should-contain [
@@ -1020,28 +1020,28 @@ f]
 scenario editor-can-undo-ctrl-b [
   # create an editor with multiple pages of text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
 e
 f]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # scroll the page down and up
   assume-console [
     press page-down
     press ctrl-b
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen should again show page 2
   screen-should-contain [
@@ -1056,28 +1056,28 @@ f]
 scenario editor-can-undo-page-up [
   # create an editor with multiple pages of text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [a
+  1:address:shared:array:character <- new [a
 b
 c
 d
 e
 f]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # scroll the page down and up
   assume-console [
     press page-down
     press page-up
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen should again show page 2
   screen-should-contain [
@@ -1092,25 +1092,25 @@ f]
 scenario editor-can-undo-ctrl-a [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor, then to start of line
   assume-console [
     left-click 2, 1
     press ctrl-a
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -1122,7 +1122,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1136,25 +1136,25 @@ ghi]
 scenario editor-can-undo-home [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor, then to start of line
   assume-console [
     left-click 2, 1
     press home
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -1166,7 +1166,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1180,25 +1180,25 @@ ghi]
 scenario editor-can-undo-ctrl-e [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor, then to start of line
   assume-console [
     left-click 2, 1
     press ctrl-e
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -1210,7 +1210,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1224,25 +1224,25 @@ ghi]
 scenario editor-can-undo-end [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor, then to start of line
   assume-console [
     left-click 2, 1
     press end
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # undo
   assume-console [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves back
   memory-should-contain [
@@ -1254,7 +1254,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1268,17 +1268,17 @@ ghi]
 scenario editor-separates-undo-insert-from-undo-cursor-move [
   # create an editor, type some text, move the cursor, type some more text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     type [abc]
     left-click 1, 1
     type [d]
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   screen-should-contain [
     .          .
     .adbc      .
@@ -1294,9 +1294,9 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # last letter typed is deleted
   screen-should-contain [
@@ -1314,9 +1314,9 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # no change to screen; cursor moves
   screen-should-contain [
@@ -1334,9 +1334,9 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # screen empty
   screen-should-contain [
@@ -1354,9 +1354,9 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # first insert
   screen-should-contain [
@@ -1374,9 +1374,9 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves
   screen-should-contain [
@@ -1394,9 +1394,9 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # second insert
   screen-should-contain [
@@ -1414,11 +1414,11 @@ scenario editor-separates-undo-insert-from-undo-cursor-move [
 scenario editor-can-undo-multiple-arrows-in-the-same-direction [
   # create an editor with some text
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # move the cursor
   assume-console [
     left-click 2, 1
@@ -1426,9 +1426,9 @@ ghi]
     press right-arrow
     press up-arrow
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 3
@@ -1438,9 +1438,9 @@ ghi]
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # up-arrow is undone
   memory-should-contain [
@@ -1452,9 +1452,9 @@ ghi]
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # both right-arrows are undone
   memory-should-contain [
@@ -1468,24 +1468,24 @@ ghi]
 scenario editor-redo-touch [
   # create an editor with some text, click on a character, undo
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def
 ghi]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   assume-console [
     left-click 3, 1
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   # redo
   assume-console [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
-    3:number <- get *2:address:editor-data, cursor-row:offset
-    4:number <- get *2:address:editor-data, cursor-column:offset
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
+    3:number <- get *2:address:shared:editor-data, cursor-row:offset
+    4:number <- get *2:address:shared:editor-data, cursor-column:offset
   ]
   # cursor moves to left-click
   memory-should-contain [
@@ -1497,7 +1497,7 @@ ghi]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1510,12 +1510,12 @@ ghi]
 
 after <handle-redo> [
   {
-    move:address:move-operation <- maybe-convert *op, move:variant
+    move:address:shared:move-operation <- maybe-convert *op, move:variant
     break-unless move
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     *cursor-row <- get *move, after-row:offset
     *cursor-column <- get *move, after-column:offset
-    top:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+    top:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
     *top <- get *move, after-top-of-screen:offset
   }
 ]
@@ -1525,24 +1525,24 @@ after <handle-redo> [
 scenario editor-can-undo-and-redo-backspace [
   # create an editor
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # insert some text and hit backspace
   assume-console [
     type [abc]
     press backspace
     press backspace
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .a         .
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1552,10 +1552,10 @@ scenario editor-can-undo-and-redo-backspace [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 3
@@ -1571,10 +1571,10 @@ scenario editor-can-undo-and-redo-backspace [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1589,38 +1589,38 @@ scenario editor-can-undo-and-redo-backspace [
 
 # save operation to undo
 after <backspace-character-begin> [
-  top-before:address:duplex-list:character <- get *editor, top-of-screen:offset
+  top-before:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
 ]
 before <backspace-character-end> [
   {
     break-unless backspaced-cell  # backspace failed; don't add an undo operation
-    top-after:address:duplex-list:character <- get *editor, top-of-screen:offset
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
+    top-after:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
     {
       # if previous operation was an insert, coalesce this operation with it
       break-unless *undo
-      op:address:operation <- first *undo
-      deletion:address:delete-operation <- maybe-convert *op, delete:variant
+      op:address:shared:operation <- first *undo
+      deletion:address:shared:delete-operation <- maybe-convert *op, delete:variant
       break-unless deletion
       previous-coalesce-tag:number <- get *deletion, tag:offset
       coalesce?:boolean <- equal previous-coalesce-tag, 1/coalesce-backspace
       break-unless coalesce?
-      delete-from:address:address:duplex-list:character <- get-address *deletion, delete-from:offset
+      delete-from:address:address:shared:duplex-list:character <- get-address *deletion, delete-from:offset
       *delete-from <- copy *before-cursor
-      backspaced-so-far:address:address:duplex-list:character <- get-address *deletion, deleted-text:offset
+      backspaced-so-far:address:address:shared:duplex-list:character <- get-address *deletion, deleted-text:offset
       insert-range backspaced-cell, *backspaced-so-far
       *backspaced-so-far <- copy backspaced-cell
       after-row:address:number <- get-address *deletion, after-row:offset
       *after-row <- copy *cursor-row
       after-column:address:number <- get-address *deletion, after-column:offset
       *after-column <- copy *cursor-column
-      after-top:address:address:duplex-list:character <- get-address *deletion, after-top-of-screen:offset
+      after-top:address:address:shared:duplex-list:character <- get-address *deletion, after-top-of-screen:offset
       *after-top <- get *editor, top-of-screen:offset
       break +done-adding-backspace-operation:label
     }
     # if not, create a new operation
-    op:address:operation <- new operation:type
-    deleted-until:address:duplex-list:character <- next *before-cursor
+    op:address:shared:operation <- new operation:type
+    deleted-until:address:shared:duplex-list:character <- next *before-cursor
     *op <- merge 2/delete-operation, save-row/before, save-column/before, top-before, *cursor-row/after, *cursor-column/after, top-after, backspaced-cell/deleted, *before-cursor/delete-from, deleted-until, 1/coalesce-backspace
     editor <- add-operation editor, op
     +done-adding-backspace-operation
@@ -1629,34 +1629,34 @@ before <backspace-character-end> [
 
 after <handle-undo> [
   {
-    deletion:address:delete-operation <- maybe-convert *op, delete:variant
+    deletion:address:shared:delete-operation <- maybe-convert *op, delete:variant
     break-unless deletion
-    start2:address:address:duplex-list:character <- get-address *editor, data:offset
-    anchor:address:duplex-list:character <- get *deletion, delete-from:offset
+    start2:address:address:shared:duplex-list:character <- get-address *editor, data:offset
+    anchor:address:shared:duplex-list:character <- get *deletion, delete-from:offset
     break-unless anchor
-    deleted:address:duplex-list:character <- get *deletion, deleted-text:offset
-    old-cursor:address:duplex-list:character <- last deleted
+    deleted:address:shared:duplex-list:character <- get *deletion, deleted-text:offset
+    old-cursor:address:shared:duplex-list:character <- last deleted
     insert-range anchor, deleted
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     *before-cursor <- copy old-cursor
     *cursor-row <- get *deletion, before-row:offset
     *cursor-column <- get *deletion, before-column:offset
-    top:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+    top:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
     *top <- get *deletion, before-top-of-screen:offset
   }
 ]
 
 after <handle-redo> [
   {
-    deletion:address:delete-operation <- maybe-convert *op, delete:variant
+    deletion:address:shared:delete-operation <- maybe-convert *op, delete:variant
     break-unless deletion
-    start:address:duplex-list:character <- get *deletion, delete-from:offset
-    end:address:duplex-list:character <- get *deletion, delete-until:offset
+    start:address:shared:duplex-list:character <- get *deletion, delete-from:offset
+    end:address:shared:duplex-list:character <- get *deletion, delete-until:offset
     remove-between start, end
     # assert cursor-row/cursor-column/top-of-screen match after-row/after-column/after-top-of-screen
     *cursor-row <- get *deletion, after-row:offset
     *cursor-column <- get *deletion, after-column:offset
-    top:address:address:duplex-list:character <- get-address *editor, top-of-screen:offset
+    top:address:address:shared:duplex-list:character <- get-address *editor, top-of-screen:offset
     *top <- get *deletion, after-top-of-screen:offset
   }
 ]
@@ -1666,9 +1666,9 @@ after <handle-redo> [
 scenario editor-can-undo-and-redo-delete [
   # create an editor
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # insert some text and hit delete and backspace a few times
   assume-console [
     type [abcdef]
@@ -1678,15 +1678,15 @@ scenario editor-can-undo-and-redo-delete [
     press delete
     press delete
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .af        .
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1696,10 +1696,10 @@ scenario editor-can-undo-and-redo-delete [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1715,10 +1715,10 @@ scenario editor-can-undo-and-redo-delete [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 2
@@ -1734,10 +1734,10 @@ scenario editor-can-undo-and-redo-delete [
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 2
@@ -1753,11 +1753,11 @@ scenario editor-can-undo-and-redo-delete [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # first line inserted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 2
@@ -1773,11 +1773,11 @@ scenario editor-can-undo-and-redo-delete [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # first line inserted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1793,11 +1793,11 @@ scenario editor-can-undo-and-redo-delete [
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # first line inserted
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1811,37 +1811,37 @@ scenario editor-can-undo-and-redo-delete [
 ]
 
 after <delete-character-begin> [
-  top-before:address:duplex-list:character <- get *editor, top-of-screen:offset
+  top-before:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
 ]
 before <delete-character-end> [
   {
     break-unless deleted-cell  # delete failed; don't add an undo operation
-    top-after:address:duplex-list:character <- get *editor, top-of-screen:offset
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
+    top-after:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
     {
       # if previous operation was an insert, coalesce this operation with it
       break-unless *undo
-      op:address:operation <- first *undo
-      deletion:address:delete-operation <- maybe-convert *op, delete:variant
+      op:address:shared:operation <- first *undo
+      deletion:address:shared:delete-operation <- maybe-convert *op, delete:variant
       break-unless deletion
       previous-coalesce-tag:number <- get *deletion, tag:offset
       coalesce?:boolean <- equal previous-coalesce-tag, 2/coalesce-delete
       break-unless coalesce?
-      delete-until:address:address:duplex-list:character <- get-address *deletion, delete-until:offset
+      delete-until:address:address:shared:duplex-list:character <- get-address *deletion, delete-until:offset
       *delete-until <- next *before-cursor
-      deleted-so-far:address:address:duplex-list:character <- get-address *deletion, deleted-text:offset
+      deleted-so-far:address:address:shared:duplex-list:character <- get-address *deletion, deleted-text:offset
       *deleted-so-far <- append *deleted-so-far, deleted-cell
       after-row:address:number <- get-address *deletion, after-row:offset
       *after-row <- copy *cursor-row
       after-column:address:number <- get-address *deletion, after-column:offset
       *after-column <- copy *cursor-column
-      after-top:address:address:duplex-list:character <- get-address *deletion, after-top-of-screen:offset
+      after-top:address:address:shared:duplex-list:character <- get-address *deletion, after-top-of-screen:offset
       *after-top <- get *editor, top-of-screen:offset
       break +done-adding-delete-operation:label
     }
     # if not, create a new operation
-    op:address:operation <- new operation:type
-    deleted-until:address:duplex-list:character <- next *before-cursor
+    op:address:shared:operation <- new operation:type
+    deleted-until:address:shared:duplex-list:character <- next *before-cursor
     *op <- merge 2/delete-operation, save-row/before, save-column/before, top-before, *cursor-row/after, *cursor-column/after, top-after, deleted-cell/deleted, *before-cursor/delete-from, deleted-until, 2/coalesce-delete
     editor <- add-operation editor, op
     +done-adding-delete-operation
@@ -1853,16 +1853,16 @@ before <delete-character-end> [
 scenario editor-can-undo-and-redo-ctrl-k [
   # create an editor
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # insert some text and hit delete and backspace a few times
   assume-console [
     left-click 1, 1
     press ctrl-k
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .a         .
@@ -1870,8 +1870,8 @@ def]
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1881,7 +1881,7 @@ def]
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1890,8 +1890,8 @@ def]
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1901,7 +1901,7 @@ def]
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # first line inserted
   screen-should-contain [
@@ -1911,8 +1911,8 @@ def]
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 1
@@ -1922,7 +1922,7 @@ def]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1934,15 +1934,15 @@ def]
 ]
 
 after <delete-to-end-of-line-begin> [
-  top-before:address:duplex-list:character <- get *editor, top-of-screen:offset
+  top-before:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
 ]
 before <delete-to-end-of-line-end> [
   {
     break-unless deleted-cells  # delete failed; don't add an undo operation
-    top-after:address:duplex-list:character <- get *editor, top-of-screen:offset
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
-    op:address:operation <- new operation:type
-    deleted-until:address:duplex-list:character <- next *before-cursor
+    top-after:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
+    op:address:shared:operation <- new operation:type
+    deleted-until:address:shared:duplex-list:character <- next *before-cursor
     *op <- merge 2/delete-operation, save-row/before, save-column/before, top-before, *cursor-row/after, *cursor-column/after, top-after, deleted-cells/deleted, *before-cursor/delete-from, deleted-until, 0/never-coalesce
     editor <- add-operation editor, op
     +done-adding-delete-operation
@@ -1954,16 +1954,16 @@ before <delete-to-end-of-line-end> [
 scenario editor-can-undo-and-redo-ctrl-u [
   # create an editor
   assume-screen 10/width, 5/height
-  1:address:array:character <- new [abc
+  1:address:shared:array:character <- new [abc
 def]
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # insert some text and hit delete and backspace a few times
   assume-console [
     left-click 1, 2
     press ctrl-u
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .c         .
@@ -1971,8 +1971,8 @@ def]
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 0
@@ -1982,7 +1982,7 @@ def]
     press ctrl-z
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -1991,8 +1991,8 @@ def]
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 2
@@ -2002,7 +2002,7 @@ def]
     press ctrl-y
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   # first line inserted
   screen-should-contain [
@@ -2012,8 +2012,8 @@ def]
     .┈┈┈┈┈┈┈┈┈┈.
     .          .
   ]
-  3:number <- get *2:address:editor-data, cursor-row:offset
-  4:number <- get *2:address:editor-data, cursor-column:offset
+  3:number <- get *2:address:shared:editor-data, cursor-row:offset
+  4:number <- get *2:address:shared:editor-data, cursor-column:offset
   memory-should-contain [
     3 <- 1
     4 <- 0
@@ -2023,7 +2023,7 @@ def]
     type [1]
   ]
   run [
-    editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+    editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   ]
   screen-should-contain [
     .          .
@@ -2035,15 +2035,15 @@ def]
 ]
 
 after <delete-to-start-of-line-begin> [
-  top-before:address:duplex-list:character <- get *editor, top-of-screen:offset
+  top-before:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
 ]
 before <delete-to-start-of-line-end> [
   {
     break-unless deleted-cells  # delete failed; don't add an undo operation
-    top-after:address:duplex-list:character <- get *editor, top-of-screen:offset
-    undo:address:address:list:address:operation <- get-address *editor, undo:offset
-    op:address:operation <- new operation:type
-    deleted-until:address:duplex-list:character <- next *before-cursor
+    top-after:address:shared:duplex-list:character <- get *editor, top-of-screen:offset
+    undo:address:address:shared:list:address:shared:operation <- get-address *editor, undo:offset
+    op:address:shared:operation <- new operation:type
+    deleted-until:address:shared:duplex-list:character <- next *before-cursor
     *op <- merge 2/delete-operation, save-row/before, save-column/before, top-before, *cursor-row/after, *cursor-column/after, top-after, deleted-cells/deleted, *before-cursor/delete-from, deleted-until, 0/never-coalesce
     editor <- add-operation editor, op
     +done-adding-delete-operation
@@ -2053,16 +2053,16 @@ before <delete-to-start-of-line-end> [
 scenario editor-can-undo-and-redo-ctrl-u-2 [
   # create an editor
   assume-screen 10/width, 5/height
-  1:address:array:character <- new []
-  2:address:editor-data <- new-editor 1:address:array:character, screen:address:screen, 0/left, 10/right
-  editor-render screen, 2:address:editor-data
+  1:address:shared:array:character <- new []
+  2:address:shared:editor-data <- new-editor 1:address:shared:array:character, screen:address:shared:screen, 0/left, 10/right
+  editor-render screen, 2:address:shared:editor-data
   # insert some text and hit delete and backspace a few times
   assume-console [
     type [abc]
     press ctrl-u
     press ctrl-z
   ]
-  editor-event-loop screen:address:screen, console:address:console, 2:address:editor-data
+  editor-event-loop screen:address:shared:screen, console:address:shared:console, 2:address:shared:editor-data
   screen-should-contain [
     .          .
     .abc       .