a1.asm

A1.asm 显示程序实验 STACK1 SEGMENT STACK DW 256 DUP(?) STACK1 ENDS DATA SEGMENT USE16 MES1 DB

;A1.asm
;显示程序实验

STACK1  SEGMENT STACK
         DW 256 DUP(?)
STACK1  ENDS

DATA	SEGMENT	USE16
MES1    DB   'Show a as hex:',0AH,0DH,'$'
SD      DB   'a'
DATA	ENDS

CODE	SEGMENT	USE16
	      ASSUME	CS:CODE,DS:DATA
	      
START: MOV 	AX,DATA
       MOV	DS,AX

       MOV  DX,OFFSET MES1         ;show message
	   MOV	AH,09H		
	   INT 	21H		

	   MOV	SI,OFFSET SD
	   MOV	AL,DS:[SI]
	   AND	AL,0F0H			
	   ;取高4位
	   SHR	AL,4
	   CMP	AL,0AH			;是否是A以上的数
	   JB	C2		
	   ADD	AL,07H		
C2:	   ADD	AL,30H		
	   MOV	DL,AL			;show character 
	   MOV	AH,02H
	   INT	21H
	   MOV	AL,DS:[SI]
	   AND	AL,0FH			;取低4位
	   CMP	AL,0AH
	   JB	C3
	   ADD 	AL,07H
C3:	   ADD	AL,30H
	   MOV	DL,AL			;show character 
	   MOV	AH,02H
	   INT	21H

	   MOV	AX,4C00H		;go back to dos
	   INT	21H
CODE  ENDS
	   END	START