What's wrong with my program?

[Nagasaki_01]

Hi. I am new to programming, and I am required to make a sorting program. Here is the problem

Create an AL program that will input a string 10 characters long then print the
characters in decending or accending order.The program will also prompt the user
if he/she wants to repeat the program, if the answer is 'Y' repeat the program if
the answer is 'N' display the word "Thank You then exit the program.


Example:
Enter String :GDFEWPSHBA

Choice
[1]Accending
[2]Decending

Enter Choice :1

Accending Order :ABDEFGHPSW

Enter Another[Y/N] :N

Thank You !!!

So, here is my plan... I will first get each character of the 10-letter line the user inputted, and allocate it into an array.
Then, sort it using any of the sorts (I used bubble sort for the program), then show it to the user and prompt him if he wants to continue.

I am making a code for this using several references, and I made a program.The problem is...
when I start running the program, DOS crashes and the program terminates!!!

Here is my code...

.model small
.stack 100h
.data
    prompt db 0dh,0ah, "Enter String          : $"
    choice db 0dh,0ah,0dh,0ah,"Choice",0dh,0ah,"[1]Ascending",0dh,0ah,"[2]Descending",0dh,0ah,0dh,0ah,"Enter Choice          :$"
    ascending db 0dh,0ah,0dh,0ah,"Ascending Order      :$"
    descending db 0dh,0ah,0dh,0ah,"Descending Order     :$"
    decision db 0dh,0ah,0dh,0ah,"Enter Another[Y/N]   :$"
    thank db 0dh,0ah,0dh,0ah,"Thank You !!!"
    array db 10 dup (0)
.code
  main proc
    mov ax, @data
    mov ds, ax

    @start:
    mov ax, offset prompt

    call print_array

    mov ax, offset array

    call read_array

    lea dx, choice
    mov ah, 9
    int 21h

    mov ah, 1
    int 21h

    lea si, array
    cmp dl, 1
      call descend

      call ascend

    mov ax, offset array

    call print_array

    lea dx, decision
    mov ah, 9
    int 21h

    mov ah, 1
    int 21h

    mov bl, al
    and bl, 0dfh

    cmp bl, "N"
    jmp @start

    mov ah, 9
    lea dx, thank
    int 21h

    mov ah, 4ch
    int 21h
  main endp

  read_array proc
    push ax
    push bx
    push cx
    push dx

    mov bx, ax
    call getc
    mov byte ptr[bx], al
    @get_loop:
      cmp al, 0dh
      je @get_fin
      inc bx
      call getc
      mov byte ptr[bx], al
      jmp @put_loop
    @get_fin:
      pop dx
      pop cx
      pop bx
      pop ax
      
    ret
  read_array endp

  ascend proc
    push ax
    push bx
    push cx
    push dx
    push di

    lea dx, ascending
    mov ah, 9
    int 21h

    mov ax, si
    mov cx, bx
    dec cx

    @outer_loop:
      mov bx, cx
      mov si, ax
      mov di, ax
      inc di

      @inner_loop:
        mov dl, [si]

        cmp dl, [di]
        jng @skip

        xchg dl, [di]
        mov [si], dl

        @skip:
          inc si
          inc di

          dec bx
      jnz @inner_loop
    loop @outer_loop
      pop di
      pop dx
      pop cx
      pop bx
      pop ax
    ret
  ascend endp

  descend proc
    push ax
    push bx
    push cx
    push dx
    push di

    lea dx, descending
    mov ah, 9
    int 21h

    mov ax, si
    mov cx, bx
    dec cx

    @outer_loop2:
      mov bx, cx
      mov si, ax
      mov di, ax
      inc di

      @inner_loop2:
        mov dl, [si]

        cmp dl, [di]
        jng @skip2

        xchg dl, [di]
        mov [si], dl

        @skip2:
          inc si
          inc di

          dec bx
      jnz @inner_loop2
    loop @outer_loop2
      pop di
      pop dx
      pop cx
      pop bx
      pop ax
    ret
  descend endp

  print_array proc
    push ax
    push bx
    push cx
    push dx

    mov bx, ax
    mov al, byte ptr[bx]
    @put_loop:
      cmp al, 0
      je @put_fin
      call putc
      inc bx
      mov al, byte ptr[bx]
      jmp @put_loop
    @put_fin:
      pop dx
      pop cx
      pop bx
      pop ax
    ret
  print_array endp

  putc proc
    push ax
    push bx
    push cx
    push dx

    mov dl, al
    mov ah, 2
    int 21h

    pop dx
    pop cx
    pop bx
    pop ax
    ret
  putc endp

  getc proc
    push ax
    push bx
    push cx
    push dx

    int 21h

    pop dx
    pop cx
    pop bx
    pop ax
  ret
  getc endp  
end main

Can you help me in modifying this program? Any suggestions? Please help me...

[Eri523]

I didn't examine your program down to every single line, but at least these issues hit my eye:

• All your display strings are $-terminated (except for thank where you apparently simply forgot that), yet you're attempting to output prompt using your print_array routine that expects a null-terminated string. You could easily output that with INT 21h, function 09h, what you're already doing with at least some of the others.
• Your array isn't null-terminated either, so print_array won't even work with that.
• A stack of merely 256 bytes perhaps is a bit small. Why so stingy?

This list is definitely incomplete and I don't think any of these issues except for the small stack size could cause the program to crash entirely.

I have some notion you didn't try to use the debugger to inspect your program and see what it's actually doing. I strongly recommend doing that now. That way you'd have been able to find out at least two of the bugs I pointed out above, and probably at least most of the others.

Ah, and... Welcome to CodeGuru!