8086-ASSEMBLY-LANGUAGE-PROGRAMS/Source Code/Introduction/hello_world_string.asm at main · Amey-Thakur/8086-ASSEMBLY-LANGUAGE-PROGRAMS · GitHub

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; =============================================================================
; TITLE: Hello World (Segmented EXE style)
; DESCRIPTION: Standard multi-segment application structure displaying
;              a string using DOS services.
; AUTHOR: Amey Thakur (https://github.com/Amey-Thakur)
; REPOSITORY: https://github.com/Amey-Thakur/8086-ASSEMBLY-LANGUAGE-PROGRAMS
; LICENSE: MIT License
; =============================================================================

; -----------------------------------------------------------------------------
; DATA SEGMENT
; -----------------------------------------------------------------------------
DATA SEGMENT
    MSG DB "Hello, World!$"
DATA ENDS

; -----------------------------------------------------------------------------
; CODE SEGMENT
; -----------------------------------------------------------------------------
CODE SEGMENT
    ASSUME CS:CODE, DS:DATA

START:
    ; Standard Initialization for Segmented EXE
    MOV AX, DATA                    ; Load segment address of DATA
    MOV DS, AX                      ; Point DS to it

    ; Prepare string output
    LEA DX, MSG                     ; Load offset of the string
    MOV AH, 09H                     ; DOS function: display string
    INT 21H                         ; Call DOS system services

EXIT:
    ; Terminate process (Standard DOS Exit)
    MOV AX, 4C00H                   ; AH=4Ch (Exit), AL=00h (Return Code)
    INT 21H                         ; Return control to MS-DOS

CODE ENDS

END START

; =============================================================================
; TECHNICAL NOTES
; =============================================================================
; 1. ARCHITECTURE:
;    - EXE files can have multiple segments (Code, Data, Stack).
;    - 'ASSUME' tells the assembler which segment register points where.
;    - 'MOV DS, AX' is required because you cannot move immediate values
;      directly into segment registers.
; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =