;A7-2.asm
;用功能調用實現子程序設計

STACK1  SEGMENT STACK
         DW 256 DUP(?)
STACK1  ENDS

DDATA	SEGMENT
CSBAK 	DW  ?
IPBAK  	DW  ?
MKBAK 	DB  ?
SW      DW  ?
MES1    DB  'The data in buf1 are:',0AH,0DH,'$'
BUF1	DB	11H,22H,33H,44H,55H,66H,77H,88H,99H,0AAH,0BBH,0CCH,0DDH,0EEH,0FFH,00H
DDATA	ENDS

CODE 	SEGMENT
        ASSUME CS:CODE,DS:DDATA
START   PROC FAR
        MOV AX,DDATA
        MOV DS,AX
  
        MOV AX,0		     ;修改47H號中斷的中斷矢量
        MOV ES,AX
        MOV DI,4*47H            
        MOV AX,ES:[DI]
        MOV IPBAK,AX		;保存原有IP
        MOV AX,OFFSET MYINT	;修改為用戶自定義中斷入口
        CLD
        STOSW
        MOV AX,ES:[DI]		;保存原有CS
        MOV CSBAK,AX
        MOV AX,SEG MYINT
        STOSW
	
	    MOV DX,OFFSET MES1	;顯示提示信息
	    MOV AH,09H
	    INT 21H

	    MOV SI,OFFSET BUF1	;顯示BUF1中的內容
	    MOV CX,10H
	    INT 47H
			
        MOV AX,0		;恢復系統中斷矢量
        MOV ES,AX
        MOV DI,4*47H            
        MOV AX,IPBAK
        CLD
        STOSW
        MOV AX,CSBAK
        STOSW

        MOV AX,4C00H		; 返回dos
        INT 21H
        RET
        ENDP
        
MYINT   PROC FAR		;自定義顯示中斷，入口參數為BL
        PUSH AX
	    PUSH DX
C1:	    MOV	AL,[SI]
	    AND	AL,0F0H		;取高4位
	    SHR	AL,4
	    CMP	AL,0AH		;是否是A以上的數
	    JB	C2		
	    ADD	AL,07H		
C2:	    ADD	AL,30H		
	    MOV	DL,AL		;顯示字符
	    MOV	AH,02H
	    INT	21H
	    MOV	AL,[SI]
	    AND	AL,0FH		;取低4位
	    CMP	AL,0AH
	    JB	C3
	    ADD AL,07H
C3:	    ADD	AL,30H
	    MOV	DL,AL		;顯示字符
	    MOV	AH,02H
	    INT	21H
	    INC	SI
	    LOOP	C1
	    POP	DX
	    POP	AX
        IRET			;中斷返回
        ENDP
CODE ENDS
     END START