PUSH	DE	being used. If it is
		CALL	Z,0C55,PO-SCR	see if the display requires
		POP	DE	to be scrolled.

Now consider the present state of INVERSE & OVER'

		PUSH	BC	Save the position values
		PUSH	HL	and the destination address
				on the machine stack.
		LD	A,(P-FLAG)	Fetch P-FLAG and read bit 0.
		LD	B,+FF	Prepare the 'OVER-mask' in
		RRA		the B register; i.e. OVER 0
		JR	C,0BA4,PR-ALL-2	= +00 & OVER 1 - +FF.
		lNC	B
0BA4	PR-ALL-2	RRA		Read bit 2 of P-FLAG and
		RRA		prepare the 'INVERSE-mask'
		SBC	A,A	in the C register; i.e.
		LD	C,A	INVERSE 0 = +00 & INVERSE
				1 = +FF.
		LD	A,+08	Set the A register to hold
		AND	A	the 'pixel-line' counter and
				clear the carry flag.
		BIT	1,(FLAGS)	Jump forward if handling
		JR	Z,0BB6,PR-ALL-3	the screen.
		SET	1,(FLAGS2)	Signal 'printer buffer no longer
				empty.
		SCP		Set the carry flag to show that
				the printer is being used.
0BB6	PR-ALL-3	EX	DE,HL	Exchange the destination
				address with the base address
				before entering the loop.

The character can now be printed. Eight passes of the loop are made - one for each 'pixel-line'.

0BB7	PR-ALL-4	EX	AF,A'F'	The carry flag is set when using
				the printer. Save this flag in F'.
		LD	A,(DE)	Fetch the existing 'pixel-line'.
		AND	B	Use the 'OVER-mask' and then
		XOR	(HL)	XOR the result with the 'pixel-
				line' of the character form.
		XOR	C	Finally consider the 'INVERSE-
				mask'.
		LD	(DE),A	Enter the result.
		EX	AF,A'F'	Fetch the printer flag and
		JR	C,0BD3,PR-ALL-6	jump forward if required.
		INC	D	Update the destination address
0BC1	PR-ALL-S	INC	HL	Update the 'pixel-line' of
				the character form.
		DEC	A	Decrease the counter and loop
		JR	NZ,0BB7,PR-ALL-4	back unless it is zero.

Once the character has been printed the attribute byte is to set as required.

		EX	DE,HL	Make the H register hold a
		DEC	H	correct high-address for the
				character area.
		BIT	1,(FLAGS)	Set the attribute byte only if
		CALL	Z,0BDB,PO-ATTR	handling the screen.
		POP	HL	Restore the original
		POP	BC	destination address and the
				position values.
		DEC	C	Decrease the column number
		INC	HL	and increase the destination
		RET		address before returning.

When the printer is being used the destination address has to be updated in increments of +20.