Bubblesort NASM

[ORG 0x100]
[BITS 16]

;----------------------------------------------------------
;                       CONSTANTS
;----------------------------------------------------------

vidmem      equ 0xb800; Start of VGA text-memory
scrw        equ 80*25   ; Size of video memory in words
eom         equ 0       ; end of message (\0, null character like C)

;----------------------------------------------------------
;                         DATA
; Description:
;   Here we define and reserve all of our global variables
;Contains:
;   int print_start -> position where printing begins
;   char color      -> color attribute (black background, white foreground)
;   char msg[]      -> message to be printed
;   char msg_end    -> termination character for msg
;   int msg_len     -> length of msg
;
;   System data and Protected Mode related data structures
;
;----------------------------------------------------------
[SECTION .data]

;-----------------------------------------------------------------------------
;-------------           APPLICATION RELATED               -------------------
;-----------------------------------------------------------------------------

print_start:    dw 160
color:          db 7
ex_array:       db '987654321'
msg_end:        db eom
array_len   db 9
msg_len:        dw (msg_end - ex_array)

;----------------------------------------------------------
;                         BSS
; Description:
;   Here we define our uninitialized variables
;   Most of the time, it is used for the stack
; Contains:
;   stack 256 bytes long, aligned to 4-byte limit
;   (start address of stack can be divided by 4)
;   stack_end       -> pointer to the next memory address after the stack
;----------------------------------------------------------
[SECTION .bss]
alignb 4

stack:          resb 256
stack_end:

;----------------------------------------------------------
;                         TEXT
; Description:
;   The part of the file containing the code
; Functions:
;   start           -> entry point of the program
;   main            -> implements our algorithm
;   cls             -> Clears the screen
;   printstr        -> Prints our message
;----------------------------------------------------------

[SECTION .text]

start:

; Initialize the stack pointer
                mov ax,cs
                mov ss,ax
                mov sp,stack_end

; Set DS register to current data segment
                mov ax,cs
                mov ds,ax

                call main

; Return to DOS
                mov ax,0x4C00
                int 0x21


;----------------------------------------------------------
; Procedure void main()
;    performs the main part of the program
;    Arguments:
;       none
;    Local Variables:
;       none
;    Returns:
;       nothing
;----------------------------------------------------------

main:

; Make Extra Segment (ES) point to videomemory
                mov ax,vidmem
                mov es,ax

; Calculate where printing stops
                mov dx,scrw
                sub dx,[msg_len]
                sal dx,1

move_msg:
                call cls
        call bubblesort
        call printstr
                ret

;----------------------------------------------------------
; Procedure void cls()
;    clears screen
;    Arguments:
;       none
;    Local Variables:
;       none
;    Returns:
;       nothing
;----------------------------------------------------------

cls:
                mov di,0            ; es:di point to start of vidmem
                mov al,' '          ; Lower byte of each char (char to print) = ' '
                mov ah,[color]      ; Higher byte of each char (color) = white
                mov cx,scrw         ; cx (repeat counter) = number of chars in screen

; Repear for cx times -> Store ax in es:di and increase di by 2
                rep stosw
                ret

;----------------------------------------------------------
; Procedure void printstr()
;    prints msg on screen, by copying each character of msg
;    at videomem starting by offset print_start.
;    Ends copying when it encounters eom
;    Arguments:
;       none
;    Local Variables:
;       none
;    Returns:
;       nothing
;----------------------------------------------------------

printstr:
        push si
        push di
                mov esi,ex_array          ; load si with offset of msg
                mov di,160          ; load di with 160

prints_loop:
                cmp byte [si],eom   ; if current char of msg == eom
                je prints_exit      ;    exit
                movsb               ; else mov[ds:si]->[es:di] - copy char to srceen
                                    ; and increase si and di
                inc di              ; di now points to color byte -> increase more
                jmp prints_loop     ; repeat

prints_exit:    pop di
        pop si

                ret
;-----------------------------BubbleSort-----------------------


bubblesort: push esi
        push edi
        push ebx
        push ax
        push dx

        xor edi,edi
        xor esi,esi
        mov ebx,ex_array
        mov esi, array_len
        inc esi

outerLoop:  dec esi
        mov edi,0
        jz end_outer

innerLoop:  inc edi
        cmp edi,esi
        ja outerLoop
        jmp compare

compare:    mov al,byte [ebx+edi*1-1]
        mov dl, byte [ebx+edi*1]
        cmp al,dl
        jng innerLoop

swap:       mov [ebx+edi*1-1],dl
        mov [ebx+edi*1],al
        jmp innerLoop

end_outer:  pop dx
        pop ax
        pop ebx
        pop edi
        pop esi

        ret

;----------------------------------------------------------
; Procedure void software_delay()
;

software_delay:
                push bx
                push cx

                mov cx,5000
outer_Loop:     mov bx,1024
inner_Loop:     dec bx
                jnz inner_Loop

                loop outer_Loop

                pop cx
                pop bx
                ret

;----------------------------------------------------------

program_end: