Assembly - Sort Bubbles to Sort Row

Question

I am writing a program in assembly using tasm. My task is to write a program that will use bubble sort to sort the entered string alphabetically. Ex. if you type hello he should write ehllo. I wrote a letter asking you to enter a string and sort it (I think it works okey to the end, where it should print the result, but in the end it just writes my .data once and ends its work) PS sorry for the bad English

.model small .stack 100h .data request db 'This program is using bubblesort to get alphabetical order of your enterd string', 0Dh, 0Ah, 'Enter your string:', 0Dh, 0Ah, '$' result db 0Dh, 0Ah, 'Result:', 0Dh, 0Ah, '$' buffer db 100, ?, 100 dup (0) .code start: MOV ax, @data MOV ds, ax MOV ah, 09h MOV dx, offset request int 21h MOV dx, offset buffer MOV ah, 0Ah INT 21h MOV si, offset buffer INC si MOV bh, [si] INC si sort: mov cx, [si] mov bx, [si] nextelement: mov ax, [bx+si] cmp ax, [bx+si+1] jge noswap xchg ax, [bx+si+1] mov ax, [bx+si] noswap: inc si cmp cx, si jl nextelement loop nextelement MOV ah, 09h MOV dx, offset result int 21h char: LODSB MOV ah, 2 MOV dl, al INT 21h DEC bh JZ ending JMP char ending: MOV ax, 4c00h INT 21h end start 

Answer 1

1) To sort the bubbles you need two nested loops. The outer loop resets the initial parameters for the inner loop until there is nothing to replace.

2) Sort characters . These are 8-bit values ​​(bytes). You cannot load them directly into a 16-bit register ( mov ax, [bx+si] ).

3) [bx+si] and [bx+si+1] : it is so wrong that I can not explain the error :-).

Instead of fixing the code, I wrote an example from scratch: after an illustration in http://en.wikipedia.org/wiki/Bubble_sort :

 .MODEL small .STACK 1000h ; Don't skimp with stack! .DATA Struct0A EQU $ ; Buffer for INT 21h/0Ah (max,got,buf) max db 100 ; Maximum characters buffer can hold (incl. CR (0Dh)) got db 0 ; Number of characters actually read, (excl. CR (0Dh)) buf db 100 dup (0) ; Actual characters read, including the final carriage return (0Dh) Linefeed db 13, 10, '$' GetString db 'Enter string: $' .CODE start: mov ax, @DATA ; Initialize DS mov ds, ax ; Input String mov ah, 09h mov dx, OFFSET GetString int 21h mov dx, OFFSET Struct0A mov ah, 0Ah INT 21h mov si, OFFSET buf ; Base for [si + bx] xor bx, bx ; Prepare BX for following byte load mov bl, got ; Load length of string = 0Dh at the end mov BYTE PTR [si + bx], '$' ; Delimiter for int 21h / 09h outer: dec bx ; The last character is already at the right place jz done ; No characters left = done mov cx, bx ; CX: loop variable mov si, OFFSET buf xor dl, dl ; DL (hasSwapped) = false inner: mov ax, [si] ; Load **two** characters cmp al, ah ; AL: 1. char, AH: 2. char jbe S1 ; AL <= AH - no change mov dl, 1 ; hasSwapped = true xchg al, ah ; Swap characters mov [si], ax ; Store swapped characters S1: inc si ; Next pair of characters loop inner test dl, dl ; hasSwapped == true? jnz outer ; yes: once more done: ; Print result mov dx, OFFSET Linefeed mov ah, 09h int 21h mov dx, OFFSET buf mov ah, 09h int 21h mov ax, 4C00h int 21h END start 

And here is another “animated” illustration:

https://www.youtube.com/watch?v=lyZQPjUT5B4