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

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; =============================================================================
; TITLE: Array Descending Sort
; DESCRIPTION: Arrange an 8-bit numeric array in descending order using
;              the bubble-exchange technique.
; AUTHOR: Amey Thakur (https://github.com/Amey-Thakur)
; REPOSITORY: https://github.com/Amey-Thakur/8086-ASSEMBLY-LANGUAGE-PROGRAMS
; LICENSE: MIT License
; =============================================================================

.MODEL SMALL
.STACK 100H

; -----------------------------------------------------------------------------
; DATA SEGMENT
; -----------------------------------------------------------------------------
.DATA
    VALUES DB 99H, 12H, 56H, 45H, 36H    ; Random input bytes
    V_LEN  EQU 5
    MSG    DB 'Array successfully sorted in Descending order.$'

; -----------------------------------------------------------------------------
; CODE SEGMENT
; -----------------------------------------------------------------------------
.CODE
START:
    ; Setup Segment
    MOV AX, @DATA
    MOV DS, AX

    MOV CX, V_LEN                       ; Outer loop counter
    DEC CX                              ; N-1 passes

    ; -------------------------------------------------------------------------
    ; DESCENDING BUBBLE LOGIC
    ; -------------------------------------------------------------------------
OUTER_SORT:
    PUSH CX
    LEA SI, VALUES                      ; Start of array

COMPARE_DESC:
    MOV AL, [SI]                        ; Element 1
    MOV BL, [SI+1]                      ; Element 2

    CMP AL, BL                          ; Compare for Descending (AL > BL)
    JAE NO_ACTION                       ; If AL >= BL, carry on

    ; SWAP
    XCHG [SI], BL                       ; Swap in memory directly
    MOV [SI+1], BL

NO_ACTION:
    INC SI                              ; Advance pointer
    LOOP COMPARE_DESC

    POP CX
    LOOP OUTER_SORT                     ; Repeat until sorted

    ; User Notification
    LEA DX, MSG
    MOV AH, 09H
    INT 21H

    ; Exit
    MOV AH, 4CH
    INT 21H

END START

; =============================================================================
; TECHNICAL NOTES
; =============================================================================
; 1. LOGIC:
;    - This is the mirror of the ascending sort.
;    - The 'JAE' (Jump if Above or Equal) is the key control flow here for
;      the descending property.
;    - Final sorted order will be: 99h, 56h, 45h, 36h, 12h.
; = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =