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1 files changed, 40 insertions, 0 deletions

diff --git a/linux/apps/ex5.subx b/linux/apps/ex5.subx
new file mode 100644
index 00000000..220a4246
--- /dev/null
+++ b/linux/apps/ex5.subx
@@ -0,0 +1,40 @@
+# Read a character from stdin, save it to a local on the stack, write it to stdout.
+#
+# To run:
+#   $ bootstrap/bootstrap translate apps/ex5.subx -o ex5
+#   $ bootstrap/bootstrap run ex5
+
+== code
+#   instruction                     effective address                                                   register    displacement    immediate
+# . op          subop               mod             rm32          base        index         scale       r32
+# . 1-3 bytes   3 bits              2 bits          3 bits        3 bits      3 bits        2 bits      2 bits      0/1/2/4 bytes   0/1/2/4 bytes
+
+Entry:
+
+    # allocate x on the stack
+    81          5/subop/subtract    3/mod/direct    4/rm32/esp    .           .             .           .           .               4/imm32           # subtract from esp
+
+    # read(stdin, x, 1)
+    # . fd = 0 (stdin)
+    bb/copy-to-ebx  0/imm32
+    # . data = x (location to write result to)
+    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none              1/r32/ecx   4/disp8         .                 # copy esp+4 to ecx
+    # . size = 1 character
+    ba/copy-to-edx  1/imm32
+    # . syscall
+    e8/call  syscall_read/disp32
+
+    # syscall(write, stdout, x, 1)
+    # . fd = 1 (stdout)
+    bb/copy-to-ebx  1/imm32
+    # . data = x (location to read from)
+    8d/copy-address                 1/mod/*+disp8   4/rm32/sib    4/base/esp  4/index/none              1/r32/ecx   4/disp8         .                 # copy esp+4 to ecx
+    # . size = 1 character
+    ba/copy-to-edx  1/imm32
+    # . syscall
+    e8/call  syscall_write/disp32
+
+    # exit(ebx)
+    e8/call  syscall_exit/disp32
+
+# . . vim:nowrap:textwidth=0