user-input - 如何在汇编语言中进行字符串输入？

Question

请问，有人知道如何用汇编语言编写字符串输入吗？我正在使用 int 21显示和输入字符。

Answer 1

您可以使用 function 0Ah 读取缓冲输入。给定一个字符串缓冲区 ds:dx它读取一个最长为 255 的字符串。缓冲区布局是:

Byte 0 String length (0-255)
Byte 1 Bytes read (0-255, filled by DOS on return)
Bytes 2-..Length+2 (The character string including newline as read by DOS).

读取字符串然后将其回显给用户的小型 COM 文件的示例:

    org 0x100

start:
    push cs
    pop ds ; COM file, ds = cs

    mov ah, 0x0A ; Function 0Ah Buffered input
    mov dx, string_buf ; ds:dx points to string buffer
    int 0x21

    movzx si, byte [string_buf+1] ; get number of chars read

    mov dx, string_buf + 2 ; start of actual string

    add si, dx ; si points to string + number of chars read
    mov byte [si], '$' ; Terminate string

    mov ah, 0x09 ; Function 09h Print character string
    int 0x21 ; ds:dx points to string

    ; Exit
    mov ax, 0x4c00
    int 0x21

string_buf: 
    db 255 ; size of buffer in characters
    db 0 ; filled by DOS with actual size
    times 255 db 0 ; actual string

请注意，它将覆盖输入行(因此它可能看起来程序没有做任何事情!)

或者，您可以使用 function 01h 并自己循环阅读字符。像这样的东西(请注意，如果输入超过 255 个字符，它会在以后的缓冲区溢出):

    org 0x100

start:
    push cs
    pop ax
    mov ds, ax
    mov es, ax; make sure ds = es = cs

    mov di, string ; es:di points to string
    cld ; clear direction flag (so stosb incremements rather than decrements)
read_loop:
    mov ah, 0x01 ; Function 01h Read character from stdin with echo
    int 0x21
    cmp al, 0x0D ; character is carriage return?
    je read_done ; yes? exit the loop
    stosb ; store the character at es:di and increment di
    jmp read_loop ; loop again
read_done:
    mov al, '$'
    stosb ; 'Make sure the string is '$' terminated

    mov dx, string ; ds:dx points to string
    mov ah, 0x09 ; Function 09h Print character string
    int 0x21

    ; Exit
    mov ax, 0x4c00
    int 0x21

string: 
    times 255 db 0 ; reserve room for 255 characters