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| -rw-r--r-- | subx/Readme.md | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/subx/Readme.md b/subx/Readme.md index d9a6cde4..f0c99421 100644 --- a/subx/Readme.md +++ b/subx/Readme.md @@ -87,8 +87,8 @@ computer. (Think of the name as short for "sub-x86".) Instructions operate on a few registers: * 6 general-purpose 32-bit registers: EAX, EBX, ECX, EDX, ESI and EDI -* 2 additional 32-bit registers: ESP and EBP, I suggest you only use these to - manage the call stack. +* 2 additional 32-bit registers: ESP and EBP (I suggest you only use these to + manage the call stack.) * 3 bit-size _flag_ registers for conditional branching: - zero/equal flag ZF - sign flag SF @@ -260,12 +260,12 @@ Instruction arguments must specify their type, from: - displacement: `/disp8` or `/disp32` - immediate: `/imm8` or `/imm32` -Different instructions (opcodes) require different operands. SubX will +Different instructions (opcodes) require different arguments. SubX will validate each instruction in your programs, and raise an error anytime you -miss or spuriously add an operand. +miss or spuriously add an argument. -I recommend you order operands consistently in your programs. SubX allows -operands in any order, but only because that's simplest to explain/implement. +I recommend you order arguments consistently in your programs. SubX allows +arguments in any order, but only because that's simplest to explain/implement. Switching order from instruction to instruction is likely to add to the reader's burden. Here's the order I've been using after opcodes: @@ -274,9 +274,9 @@ reader's burden. Here's the order I've been using after opcodes: /subop /mod /rm32 /base /index /scale /r32 /displacement /immediate ``` -Instructions can refer to labels in displacement or immediate operands, and -they'll obtain a value based on the address of the label: immediate operands -will contain the address directly, while displacement operands will contain +Instructions can refer to labels in displacement or immediate arguments, and +they'll obtain a value based on the address of the label: immediate arguments +will contain the address directly, while displacement arguments will contain the difference between the address and the address of the current instruction. The latter is mostly useful for `jump` and `call` instructions. @@ -302,9 +302,9 @@ to call it is up to you. I try to keep things simple so that there's less work to do when I eventually implement SubX in SubX. But there _is_ one convenience: instructions can -provide a string literal surrounded by quotes (`"`) in an `imm32` operand. +provide a string literal surrounded by quotes (`"`) in an `imm32` argument. SubX will transparently copy it to the `data` segment and replace it with its -address. Strings are the only place where a SubX operand is allowed to contain +address. Strings are the only place where a SubX word is allowed to contain spaces. That should be enough information for writing SubX programs. The `examples/` |