汇编学习笔记25

第25讲，循环程序设计

 

例：

有一组字节数据，从中找出第一个非0的数，输出下标

 

DATA SEGSEMT

ARRAY DB 0,0,0,0,0,02H,…….

COUNT EQU $ – ARRAY

DATA ENDS

 

CODE SEGMENT

  ASSUME CS: CODE, DS: DATA

START:MOV AX, DATA

MOV DS, AX

MOV DI, OFFSET ARRAY

MOV CX, COUNT

DEC DI

AGAIN: INC DI

CMP [DI], 0

LOOPZ AGAIN

MOV DX, DI

OR DL, 30H

DISPLAY: MOV AH, 02H

INT 21H

MOV AH, 4CH

INT 21H

CODE ENDS

END START

例

把字符串中所有大写字母改为小写字母

DATA SEGMENT

STR DB 'HellO WOrlD !!', 0

DATA ENDS

CODE SEGMENT

  ASSUME CS: CODE, DS: DATA

START: MOV AX, DATA

MOV DS, AX

MOV DI, OFFSET STR

AGAIN: MOV AL, [DI]

OR AL, AL

JZ OK

CMP AL, 'A'

JB SKIP

CMP AL, 'Z'

JA SKIP

OR AL 20H

MOV [DI] AL

SKIP: INC DI

JMP AGAIN

OK: MOV AX, 4C00H

INT 21H

CODE ENDS

END START