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Anatomy of assembly code

The assembler processes the source file one line at a time. Lines are trimmed before processing so leading spaces and tab characters can be inserted for better formatting if desired. Each line could be one of the following types:

- Blank line                : Will be ignored
- Comment                      : Starts with semicolon (;)
- Instruction               : Syntactically valid Hieritage/1 instruction
- Label                     : Symbolic address. Start with colon (:)
- Symbol definition         : In the form SYMBOL equ VALUE, or: #define SYMBOL = VALUE
- Origin directive             : In the form #org ADDRESS
- Data directive            : In the form #data EXPRESSION
- Output Format directive   : In the form #format FORMAT
- Include directive         : In the form #include FILE_NAME

Comments cannot appear in a line that is not a comment. Following is an example of acceptable assembly code.

; Listing #1
; ----------------------------------------------------
; HERITAGE/1 -- SAMPLE ASSEMBLY CODE
; ----------------------------------------------------
; This code implements INT 7 both vector and handler code
;   for copying BUFF_SIZE words from BUFF_SRC to BUFF_DES
;
#format H12
#include vectors.equ
        INT_7_CODE      equ     0x0400
        BUFF_SRC        equ     0x4000
        BUFF_DES        equ     0x0800
        BUFF_SIZE       equ     0x0020
    
#org    INT_7_VECTOR
#data   INT_7_CODE

#org    INT_7_CODE
         mvi        c,    BUFF_SIZE
         mvi        d,     BUFF_SRC
         mvi        e,    BUFF_DES
:LOOP
         ldx        a, d
         stoxa, e
         inc        d
         inc        e
         dec        c
         jnz        LOOP
         jp        QUIT

; garbage, just to justify the forward jump
#data    0xffff            

:QUIT
    ret