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

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; =============================================================================
; TITLE: Basic Procedure Execution
; DESCRIPTION: Demonstrate the use of subroutines to avoid code duplication
;              for repetitive tasks like numeric scaling.
; AUTHOR: Amey Thakur (https://github.com/Amey-Thakur)
; REPOSITORY: https://github.com/Amey-Thakur/8086-ASSEMBLY-LANGUAGE-PROGRAMS
; LICENSE: MIT License
; =============================================================================

ORG 100H                            ; Standard COM entry point

; -----------------------------------------------------------------------------
; MAIN EXECUTION FLOW
; -----------------------------------------------------------------------------
START:
    MOV AL, 01H                         ; Initial value
    MOV BL, 02H                         ; Scaling factor

    ; Repeatedly double the value in AL by invoking the M2 procedure
    CALL M2                             ; AL = 2
    CALL M2                             ; AL = 4
    CALL M2                             ; AL = 8
    CALL M2                             ; AL = 16

    ; Return back to the shell
    RET

; -----------------------------------------------------------------------------
; SUBROUTINE: M2
; Description: Multiplies AL by BL. Result returns in AX.
; -----------------------------------------------------------------------------
M2 PROC
    MUL BL                              ; Multiply accumulator by BL
    RET                                 ; Jump back to the caller (POP IP)
M2 ENDP

END

; =============================================================================
; TECHNICAL NOTES
; =============================================================================
; 1. PROCEDURES:
;    - Procedures (Procs) encapsulate reusable logic.
;    - The 'CALL' instruction pushes the IP (Instruction Pointer) onto the stack.
;    - The 'RET' instruction pops that address back into the IP to resume flow.
;    - This reduces the binary size compared to inline macro expansion.
; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =