这个都是过去DOS时代的汇编源码，虽然已经过去了，但是对于学习汇编还是有帮助的，汇编语言只是程序员一门基础语言，大多人掌握即可，不一定要深入研究.......
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TITLE CALC
CGROUP GROUP CODESEG
CODESEG SEGMENT PARA PUBLIC 'CODE'
ASSUME CS:CGROUP,DS:CGROUP,ES:CGROUP
PUBLIC CALC
ORG 100H
CALC PROC FAR
JMP START
;---------------------------------------------------------------------;
; ;
; DATA AREA ;
; ;
;---------------------------------------------------------------------;
DB 'INTERRUPT NUMBER ='
INT_NUMBER DB 61h
SCREEN_HANDLE DW 0001h
MESSAGE DB 'PEMATH is not resident',13,10
MESSAGE_LEN EQU $-MESSAGE
TAG DB 'PEMATH'
TAG_LEN EQU $-TAG
;---------------------------------------------------------------------;
; ;
; CODE AREA ;
; ;
;---------------------------------------------------------------------;
START:
;---------------------------------------------------------------------;
; TEST FOR PRESENCE OF CALCULATOR ;
;---------------------------------------------------------------------;
SUB AX,AX
MOV ES,AX
SUB BH,BH
MOV BL,INT_NUMBER
SHL BX,1
SHL BX,1
MOV DI,ES:[BX]
MOV ES,ES:[BX+2]
ADD DI,4
LEA SI,TAG
MOV CX,TAG_LEN
REPE CMPSB
JE CALL_CALC
MOV BX,SCREEN_HANDLE
MOV CX,MESSAGE_LEN
LEA DX,MESSAGE
MOV AH,40h
INT 21h
JMP SHORT CALC_EXIT
;---------------------------------------------------------------------;
; CALL CALCULATOR ;
;---------------------------------------------------------------------;
CALL_CALC:
MOV AL,INT_NUMBER
MOV BYTE PTR INT_CODE,AL
DB 0CDh ; INT
INT_CODE:
DB 00h
NOP
NOP
CALC_EXIT:
INT 20h
CALC ENDP
CODESEG ENDS
END CALC