Spectrum ROM: Routine at 17F9

17F9: THE 'LIST' ENTRY POINT

The address of this routine is found in the parameter table. The 'main screen' channel will need to be opened.
LIST	17F9	LD A,$02	Use stream +02.
This entry point is used by the routine at LLIST.
LIST_1	17FB	LD (IY+$02),$00	Signal 'an ordinary listing in the main part of the screen' (reset bit 4 of TV-FLAG and all other bits).
	17FF	CALL SYNTAX_Z	Open the channel unless checking syntax.
	1802	CALL NZ,CHAN_OPEN	Open the channel unless checking syntax.
	1805	RST $18	With the present character in the A register see if the stream is to be changed.
	1806	CALL STR_ALTER
	1809	JR C,LIST_4	Jump forward if unchanged.
	180B	RST $18	Is the present character a ';'?
	180C	CP ";"	Is the present character a ';'?
	180E	JR Z,LIST_2	Jump if it is.
	1810	CP ","	Is it a ','?
	1812	JR NZ,LIST_3	Jump if it is not.
LIST_2	1814	RST $20	A numeric expression must follow, e.g. LIST #5,20.
	1815	CALL CLASS_06	A numeric expression must follow, e.g. LIST #5,20.
	1818	JR LIST_5	Jump forward with it.
LIST_3	181A	CALL USE_ZERO	Otherwise use zero and also jump forward.
	181D	JR LIST_5	Otherwise use zero and also jump forward.
Come here if the stream was unaltered.
LIST_4	181F	CALL FETCH_NUM	Fetch any line or use zero if none supplied.
LIST_5	1822	CALL CHECK_END	If checking the syntax of the edit-line move on to the next statement.
	1825	CALL FIND_INT2	Line number to BC.
	1828	LD A,B	High byte to A.
	1829	AND $3F	Limit the high byte to the correct range and pass the whole line number to HL.
	182B	LD H,A
	182C	LD L,C
	182D	LD ($5C49),HL	Set E-PPC and find the address of the start of this line or the first line after it if the actual line does not exist.
	1830	CALL LINE_ADDR
This entry point is used by the routine at AUTO_LIST.
LIST_ALL	1833	LD E,$01	Flag 'before the current line'.
Now the controlling loop for printing a series of lines is entered.
LIST_ALL_1	1835	CALL OUT_LINE	Print the whole of a BASIC line.
	1838	RST $10	This will be a 'carriage return'.
	1839	BIT 4,(IY+$02)	Jump back unless dealing with an automatic listing (bit 4 of TV-FLAG set).
	183D	JR Z,LIST_ALL_1
	183F	LD A,($5C6B)	Also jump back if there is still part of the main screen that can be used (DF-SZ <> S-POSN-hi).
	1842	SUB (IY+$4F)
	1845	JR NZ,LIST_ALL_1
	1847	XOR E	A return can be made at this point if the screen is full and the current line has been printed (E=+00).
	1848	RET Z
	1849	PUSH HL	However if the current line is missing from the listing then S-TOP has to be updated and a further line printed (using scrolling).
	184A	PUSH DE
	184B	LD HL,$5C6C
	184E	CALL LN_FETCH
	1851	POP DE
	1852	POP HL
	1853	JR LIST_ALL_1