;* MAKE A BITMAP BY COMPARING TWO FILES

.Z80			;Z80 NMEMONICS

	LD	HL,3000h		;ONE FILE
	LD	DE,4000h		;THE OTHER FILE
	LD	BC,8000h		;BYTE OF THE BITMAP
	LD	A,8			;BIT COUNT
	LD	(7FFFh),A		;STORE BIT COUNT


BITCK:	LD	A,(DE)
	CP	(HL)
	ld	a,(bc)			;get byte being assembled in bit map
	JR	Z,SAME
	SET	7,a			;make high bit a 1
	JR	BYTECK
SAME:	RES	7,a			;make high bit a 0
BYTECK:	ld	(bc),a			;store assembled byte back into bit map
	ld	a,(7FFFh)		;count of bits done
	dec	a
	JR	NZ,samebt		;if 8 bits not done in this byte
	set	3,a			;make count 8 again
	inc	bc			;point to next byte in bit map
samebt:	ld	(7FFFh),a		;store bit count

	ld	a,(bc)			;get byte being assembled in bit map
	SRA	a			;shift all bits right one place
	ld	(bc),a			;store assembled byte back into bit map

	INC	HL			;one file
	INC	DE			;the other file

	LD	A,H			;file began at 3000 h
	cp	40H			;SET TO DO 1000 H BYTES
	jr	nz,bitck
	JP	Z,0			;WARM BOOT

	end