PAGE    ,132

	       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