【汇编语言】王爽第三版 - 实验11

把以0结尾的字符串小写转大写 

DATAS SEGMENT
    ;此处输入数据段代码
    db "Beginner's All-purpose Symbolic Instruction Code.",0

DATAS ENDS

STACKS SEGMENT
    ;此处输入堆栈段代码
STACKS ENDS

CODES SEGMENT
    ASSUME CS:CODES,DS:DATAS,SS:STACKS
START:
    MOV AX,DATAS
    MOV DS,AX
    ;此处输入代码段代码
    MOV SI,0
    MOV CX,0
    CALL letterc  
    MOV AH,4CH
    INT 21H

letterc: 
push cx
push si

s:mov CL,[SI]
jcxz over
cmp CL,61h
jb s0
cmp CL,7ah
ja s0
and byte ptr [SI],11011111b
inc SI
jmp s

s0:inc si
   jmp short s
over:
pop si
pop cx
ret



CODES ENDS
    END START