.TITLE XFRC
.GLOBL XFRC
XFRC:: MOV	4(R5),R1
	CMP	R1,#-1
	BNE	OKARG
	DEC	(R5)
	JSR	PC,LEN      ;GET 'LEN' FROM CALLING PROGRAM.
	INC	(R5)
	TST	R0
	BPL	OKLEN
ERROR:	CLR	R0
	RTS	PC
OKARG:	MOV	@R1,R0
	BLE	ERROR
OKLEN:	MOV	2(R5),R1       ;MOVE INPUT BASE ADDRS TO R1
       MOV 6(R5),R2       ;MOVE OUTPUT BASE ADDRS TO R2.
	CMP	R1,R2
	BLO	BACK
IO:    MOVB (R1)+,(R2)+   ;OUTPUT=INPUT BYTE BY BYTE.
       SOB R0,IO          ;DONE? NO THEN BACK TO IO. YES? RETURN
	DEC	R0	;-1 MEANS SUCCESS
	RTS	PC
BACK:	ADD	R0,R1
	ADD	R0,R2
LUP:	MOVB	-(R1),-(R2)
	SOB	R0,LUP
	DEC	R0
	RTS	PC
.END