0A80	PO-CHANGE	LD	HL,(CURCHL)	HL will point to the 'output'
				routine address.
		LD	(HL),E	Enter the new 'output'
		INC	HL	routine address and thereby
		LD	(HL),D	force the next character code
		RET		to be considered as an operand.

Once the operands have been collected the routine continues.

0A87	PO-CONT	LD	DE,+09F4	Restore the original address
		CALL	0A80,PO-CHANGE	for PRINT-OUT (+09F4).
		LD	HL,(TVDATA)	Fetch the control code and the
				first operand if there are indeed
				two operands.
		LD	D,A	The 'last' operand and the
		LD	A,L	control code are moved.
		CP	+16	Jump forward if handling
		JP	C,2211,CO-TEMPS	INK to OVER.
		JR	NZ,0AC2,PO-TAB	Jump forward if handling TAB.

Now deal with the AT control character.

		LD	B,H	The line number.
		LD	C,D	The column number.
		LD	A,+1F	Reverse the column number;
		SUB	C	i.e. +00 - +1F becomes +1F -
				+00.
		JR	C,0AAC,PO-AT-ERR	Must be in range.
		ADD	A,+02	Add in the offset to give
		LD	C,A	C holding +21 - +22.
		BIT	1,(FLAGS)	Jump forward if handling the
		JR	NZ,0ABF,PO-AT-SET	printer.
		LD	A,+16	Reverse the line number;
		SUB	B	i.e. +00 - +15 becomes +16 -
				+01.
0AAC	PO-AT-ERR	JP	C,1E9F,REPORT-B	If appropriate jump forward.
		INC	A	The range +16 - +01 becomes
		LD	B,A	+17 - +02.
		INC	B	Andnow +18 - +03.
		BIT	0,(TV-FLAG)	If printing in the lower part
		JP	NZ,0C55,PO-SCR	of the screen then consider
				whether scrolling is needed.
		CP	(DF-SZ)	Give report 5 - Out of screen,
		JP	C,0C86,REPORT-5	if required.
0ABF	PO-AT-SET	JP	0D09,CL-SET	Return via CL-SET & PO-STORE.

And the TAB control character.

0AC2	PO-TAB	LD	A,H	Fetch the first operand.
OAC3	PO-FILL	CALL	0B03,PO-FETCH	The current print position.
		ADD	A,C	Add the current column value.
		DEC	A	Find how many 'spaces', modulo
		AND	+1F	32, are required and return
		RET	Z	if the result is zero.
		LD	D,A	Use 0 as the counter.
		SET	0,(FLAGS)	Suppress 'leading space'.
0A00	PO-SPACE	LD	A,+20	Print 'D number' of
		CALL	0C3B,PO-SAVE	spaces.
		DEC	D
		JR	NZ,0AD0,PO-SPACE
		RET		Now finished.

PRINTABLE CHARACTER CODES.
The required character (or characters) is printed by calling PO-ANY followed by PO-STORE.