汇编语言实验11

编写子程序，实现大小写转换

data    segment    db  "Beginner`s All-purpose Symbolic Instruction Code.",0data    endscodesg segmentassume cs:codesgstart:    mov ax,data    mov ds,ax    mov si,0    call letterc    mov ax,4c00h    int 21h    ;功能：将一个字符串的小写字母全转换为大写    ;参数：ds:si表示字符串首地址，字符串以0结尾letterc:    mov al,[si]    test al,al    jz lettercend    cmp al,'a'    jl notjump    cmp al,'z'    jg notjump    and al,0dfh    mov [si],alnotjump:    inc si    jmp letterclettercend:    retcodesg endsend start

注意每个字母占一字节，寄存器使用AL，不要写成AX