【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