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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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;* HELLOMO.ASM illustrates old techniques of multiple-module
;* programming. It uses full segment definitions, pushes arguments
;* and calls procedures explicitly, sets up its own stack frame,
;* and shares data using PUBLIC and EXTERN.
;*
;* To build the program, paste HELLOMO.ASM and PUTSTRO.ASM into
;* separate files, compile both, and link. For a similar example
;* that uses new techniques such as INVOKE, PROTO, and extended
;* PROC, see HELLOM.ASM.
;*
;* Shows:   Instructions  - call
;*          Directives    - SEGMENT     ENDS       GROUP
;*                          PUBLIC      EXTERN     END
;*          DOS Functions - 4Ch (Exit Program with Return Code)
 
        .DOSSEG                         ; Force DOS segment order
DGROUP  GROUP   _DATA, STACK            ; Stack and data in DGROUP
 
STACK   SEGMENT PARA STACK 'STACK'
        DB      100h DUP (?)            ; 256-byte stack
STACK   ENDS
 
_DATA   SEGMENT WORD PUBLIC 'DATA'      ; Data segment with string data
msg     DB      "Hello, world.", 13, 10, 0      ; Null-terminated string
_DATA   ENDS
 
_TEXT   SEGMENT WORD PUBLIC 'CODE'      ; Code segment
        ASSUME  cs:_TEXT, ds:DGROUP, ss:DGROUP
start:
        mov     ax, DGROUP              ; Initialize data segment
        mov     ds, ax
 
        EXTERN  C putstr:NEAR           ; Declare as C external near symbol
        mov     ax, OFFSET msg          ; Load address of data and
        push    ax                      ;  push as function argument
        call    putstr                  ; Call function
 
        mov     ax, 4C00h               ; Exit functions with 0 in AL
        int     21h                     ; Exit Program with Return Code
 
_TEXT   ENDS
        END     start                   ; Specify label of start address
                                    -♦-