;                 PDS DEMONSTRATION PROGRAM
;
;THIS PROGRAM ADDS TWO NUMBERS IN PACKED BCD FORMAT, AND CONVERTS THE
;SUM TO AN ASCII STRING.  THE TWO NUMBERS ARE STORED IN CONSECUTIVE
;MEMORY BYTES AS:
;
;R0 ->  FIRST BYTE  = LEAST AND NEXT LEAST SIGNIFICANT DIGITS OF AUGEND
;       SECOND BYTE = NEXT TWO MOST SIGNIFICANT DIGITS OF AUGEND
;       THIRD BYTE  = MOST AND NEXT MOST SIGNIFICANT DIGITS OF AUGEND
;       FOURTH BYTE = \
;       FIFTH BYTE  =  >  SAME FOR ADDEND
;       SIXTH BYTE  = /
;
;THE RESULT IS RETURNED IN A STRING POINTER TO BY R1.
;
;*************************************************************************
	ORG	0040H
	ROX	EQU	00H	;PSEUDONYM FOR R0
DEMO:	MOV	R1,#BUFFER	;GET POINTER TO RESULTS AREA
	MOV	R1,#03		;SET BCD DIGITS COUNTER
	CLR	CY		;GET READY FOR ADDITION ACCTION
	PUSH	ROX		;SAVE PARAMETER POINTER
LOOP:	MOV	A,@R0		;GET TWO BCK DIGITS FROM AUGEND
	INC	RO		;POINT TO CORRESPONDING DIGITS IN ADDEND
	INC	R0		;  ("INC" DOESN'T AFFECT CARRY FLAG)
	INC	R0
	ADDC	A,@R0		;ADD THE TWO TOGETHER
	DA	A		;ADJUST FOR DECIMAL ARITHMETIC
	PUSKH	ACC		;SAVE RESULT
	ANL	A,#0FH		;GET LOWER DIGIIT
	ORL	A,#30H		;CONVERT LOWER DIGIT TO ASCII
	MV	@R1,A		;PUT INTO
	INC	R1		;POINT TO NEXT RESULT BUFFER LOCATION
	POP	ACC		;GET BACK RESULT O ADDITION
	SWAP	A		;GET UPPER DIGIT
;DELETE THIS COMMENT
	ANL	A,#0FH
	ORL	A,#30H		;CONVERT TO ASCII
	MOV	@R1,A		;PUT INTO RESULT BUFFER
	INC	R1		;POINT TO NEXT RESULT BUFFER LOCATION
	DEC	R0		;POINT TO NEXT TWO BCD DIGITS IN AUGEND
	DEC	R0		;  ("DEC" DOESEN'T AFFECT CARRY FLAG)
	DJNZ	R2,LOOP		;LAST PAIR OF BCD DIGITS ADDED?
				;  NO--ADD TWO MORE
				;  YES--CHECK LAST DIGIT OF SUM