Org and end

docs/redcode/parser.md

@@ -10,6 +10,32 @@ The parser performs the following functions:
 * Executes [preprocessor commands](preprocessor)
 * Removes white space and [comments](comments)
 
+## Org and End Directives
+
+By default, warriors are loaded into core with the first instruction as the starting instruction.
+
+The `org` directive allows a different starting address to be specified. The `org` directive should be written on its own line and followed by an address indicating the start address relative to the first address in the warrior.
+
+By convention, the `org` directive is usually placed at the top of the warrior's code.
+
+```
+org 1
+dat #4, #0
+add.ab -1, -1
+```
+
+The above example uses the `org` directive to set the first instruction to the `add` instruction rather than the `dat` instruction.
+
+The `org` directive was introduced in the [ICWS'94](./#standards) standard. Previous standards used the `end` directive instead, which worked in the same way but was placed at the end of the warrior.
+
+```
+dat #4, #0
+add.ab -1, -1
+end 1
+```
+
+Note the `end` and `org` directives are semantically equivalent and either can be used.
+
 ## Defaults
 
 All instructions require a [modifier](modifiers) and two [operands](operands) in order to be loaded into the `Simulator`.  Each operand must have an [addressing mode](addressing_modes) and a number.
@@ -18,11 +44,17 @@ However, it is not necessary to specify modifiers or addressing modes in order f
 
 For example when parsed `mov 0, 1` will become `MOV.I $0, $1`.
 
-Under the [ICWS'94 standard](./#standards), the [direct](addressing_modes#direct) (`$`) addressing mode is always the default addressing mode, and the parser will always insert this if the addressing mode is ommitted.
+### Addressing Modes
+
+The default addressing mode is [direct](addressing_modes#direct) (`$`) for all [opcodes](opcodes) except [dat](opcodes#dat-data). Instructions with the `dat` opcode default to the [immediate](addressing_modes#immediate) (`#`) addressing mode.
+
+### Operands
+
+If an instruction has only a single operand, the `B` operand is defaulted to zero. Only the `dat`, `jmp`, `spl` and `nop` opcodes can have a single operand specified. Failure to specify a `B` operand for other opcodes will result in a syntax error.
 
-Older standards inserted the [immediate](addressing_modes#immediate) (`#`) addressing mode if the opcode of the instruction was [dat](opcodes#dat-data).
+### Modifiers
 
-Which modifier is inserted as a default is dependant upon the instruction's [opcode](opcodes) and `A` and `B` addressing modes as follows:
+Which modifier is inserted as a default is dependant upon the instruction's opcode and `A` and `B` addressing modes as follows:
 
 |Opcode|A-mode|B-mode|Default Modifier|
 |---|---|---|---|
@@ -37,3 +69,10 @@ Which modifier is inserted as a default is dependant upon the instruction's [opc
 ||$@<>{}|any|`.b`|
 |`jmp``jmz``jmn``djn``spl``nop`|any|any|`.b`|
 
+### ORG (Starting address)
+
+If no `ORG` or `END` directive is specified, the `ORG` directive will be used to determine the start address.
+
+If multiple `ORG` or `END` directives are detected, the last one will be used (with `ORG` taking precedence over `END`).
+
+Both these situations will generate a parser warning.

mkdocs.yml

@@ -6,6 +6,7 @@ pages:
    - Intro: corewar/index.md
    - Core: corewar/core.md
    - Warriors: corewar/warriors.md
+   - Loader: corewar/loader.md
 - Redcode Reference:
    - Intro: redcode/index.md
    - Execution: redcode/execution.md