ADD al，"0"有什么作用?为什么在打印整数之前使用它? [英] What does ADD al, '0' do, and why use it before printing an integer digit?

问题描述

我是汇编语言编程的新手
我搜索了二进制搜索程序，并找到了它，然后尝试理解该程序.它工作正常，但我无法理解代码的成功部分:

I am a novice in assembly language programming
I searched for binary search program and found this and I tried understand the program. It's working fine but I couldn't understand the success part of the code:

什么是ADD al,'0'，什么是mov res,al?

.model small
.stack 100h
.data
    ARR DW 1000H,2000H,3000H,4000H,5000H,6000H
    LEN DW ($-ARR)/2
    KEY EQU 2000H
    SUC DB "KEY IS FOUND AT$"
    FAILURE DB "KEY IS NOT FOUND$"
    RES DB "POSITION",13,10,"$"
.CODE
    START:
        MOV AX,@data
        MOV DS,AX
        MOV BX,00           ;LOW
        MOV DX,LEN          ;HIGH
        MOV CX,KEY          ;KEY
    AGAIN:
        CMP BX,DX
        JA FAIL
        MOV AX,BX
        ADD AX,DX
        SHR AX,1
        MOV SI,AX
        ADD SI,SI
        CMP CX,ARR[SI]
        JAE BIG             
        DEC AX          
        MOV DX,AX
        JMP AGAIN
    BIG:
        JE SUCCESS      
        INC AX          
        MOV BX,AX
    JMP AGAIN
    SUCCESS:
        ADD AL,01
        ADD AL,'0'
        MOV RES,AL
        LEA DX SUC
        JMP DISP
    FAIL:
        LEA DX,FAILURE
    DISP:
        MOV AH,09H
        INT 21H
        MOV AH,4CH
        INT 21H
    END START

推荐答案

add al, '0'将一些1位数字转换为相应的ASCII码，以便在成功时将其作为结果值显示在屏幕上.

add al, '0' converts some 1 digit number to the corresponding ASCII code in order to display it at the screen as a result value on success.

mov res, al将寄存器AL的值存储在变量RES的第一个字节中.只要RES指向字符串'POSITION',13,10,'$'，AL的值将存储在该字符串的字符'P'的顶部，并且如果例如AL = 33h，则该字符串变为'3OSITION',13,10,'$'.

mov res, al stores the value of the register AL in the first byte of the variable RES. As long as RES points to a string 'POSITION',13,10,'$', the value of AL will be stored on top of the character 'P' of this string and if, for example AL=33h, the string becomes '3OSITION',13,10,'$'.

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