在汇编中反转字符串 (TASM)

Question

我是汇编语言的新手，我在反转字符串时遇到问题。

例如：

原始字符串："ABCD"
反转后："DCBA"

我也想将反转后的字符串放入我使用的相同变量名中，而不是使用新的。我考虑过使用堆栈，这是我编写的代码，但我不知道我的错误在哪里：

IDEAL 
MODEL small
STACK 1000h

DATASEG

first db 'ABCD', 0

CODESEG

start:
    mov ax, @data
    mov ds, ax
    mov si, 0
    mov di, 0

loop_start:
    mov ax, [first+si]
    inc si
    test ax, ax
    jz done1ax

    push ax
    jmp loop_start

done1ax:
        pop ax
        mov [first+di], ax
        inc di
        cmp di, si
        JL done1ax

 mov dl, 10
 mov ah, 2
 int 21h
 ret

END start

Answer 1

让我详细说明@Michael 的评论：

IDEAL
MODEL small
STACK 1000h

DATASEG

first db 'ABCD', 0

CODESEG

start:
    mov ax, @data
    mov ds, ax
    xor si, si              ; mov si, 0
    xor di, di              ; mov di, 0

loop_start:
    mov al, [first+si]
    inc si
    test al, al
    jz done1ax

    push ax                 ; pushes implicit `AL`
    jmp loop_start

done1ax:
    pop ax                  ; pops `AL` and `AH`, `AH` isn't used
    mov [first+di], al
    inc di
    cmp di, si
    jb done1ax              ; jl is signed comparison: 8000h < 7FFFh

mov ah, 40h                 ; WriteFile
mov bx, 1                   ; STDOUT
mov cx, 4                   ; Number of bytes to write
mov dx, OFFSET first        ; Data to write
int 21h

mov ax, 4C00h               ; Return 0
int 21h

END start

在汇编中反转字符串 (TASM)

reversing a string in assembly (TASM)

assembly

tasm