Spectrum ROM: Routine at 06437

06437: THE 'PRINTING CHARACTERS IN A BASIC LINE' SUBROUTINE

All of the character/token codes in a BASIC line are printed by repeatedly calling this subroutine.
OUT_SP_2	06437	LD A,E	The A register will hold 32 for a space or 255 for no-space.
	06438	AND A	Test the value and return if there is not to be a space.
	06439	RET M	Test the value and return if there is not to be a space.
	06440	JR OUT_CHAR	Jump forward to print a space.
This entry point is used by the routine at OUT_NUM_1 to print a line number that may (E=32) or may not (E=255) require leading spaces.
OUT_SP_NO	06442	XOR A	Clear the A register.
The HL register pair holds the line number and the BC register the value for 'repeated subtraction' (-1000, -100 or -10).
OUT_SP_1	06443	ADD HL,BC	The 'trial subtraction'.
	06444	INC A	Count each 'trial'.
	06445	JR C,OUT_SP_1	Jump back until exhausted.
	06447	SBC HL,BC	Restore last 'subtraction' and discount it.
	06449	DEC A	Restore last 'subtraction' and discount it.
	06450	JR Z,OUT_SP_2	If no 'subtractions' were possible jump back to see if a space is to be printed.
	06452	JP OUT_CODE	Otherwise print the digit.
This entry point is used by the routine at OUT_LINE to print a character or token.
OUT_CHAR	06455	CALL NUMERIC	Return carry reset if handling a digit code.
	06458	JR NC,OUT_CH_3	Jump forward to print the digit.
	06460	CP 33	Also print the control characters and 'space'.
	06462	JR C,OUT_CH_3	Also print the control characters and 'space'.
	06464	RES 2,(IY+1)	Signal 'print in K-mode' (reset bit 2 of FLAGS).
	06468	CP 203	Jump forward if dealing with the token 'THEN'.
	06470	JR Z,OUT_CH_3	Jump forward if dealing with the token 'THEN'.
	06472	CP ":"	Jump forward unless dealing with ':'.
	06474	JR NZ,OUT_CH_1	Jump forward unless dealing with ':'.
	06476	BIT 5,(IY+55)	Jump forward to print the ':' if in 'INPUT mode' (bit 5 of FLAGX set).
	06480	JR NZ,OUT_CH_2
	06482	BIT 2,(IY+48)	Jump forward if the ':' is 'not in quotes' (bit 2 of FLAGS2 reset), i.e. an inter-statement marker.
	06486	JR Z,OUT_CH_3
	06488	JR OUT_CH_2	The ':' is inside quotes and can now be printed.
OUT_CH_1	06490	CP "\""	Accept for printing all characters except '"'.
	06492	JR NZ,OUT_CH_2	Accept for printing all characters except '"'.
	06494	PUSH AF	Save the character code whilst changing the 'quote mode'.
	06495	LD A,(23658)	Fetch FLAGS2 and flip bit 2.
	06498	XOR 4	Fetch FLAGS2 and flip bit 2.
	06500	LD (23658),A	Enter the amended value into FLAGS2 and restore the character code.
	06503	POP AF
OUT_CH_2	06504	SET 2,(IY+1)	Signal 'the next character is to be printed in L-mode' (set bit 2 of FLAGS).
OUT_CH_3	06508	RST 16	The present character is printed before returning.
	06509	RET	The present character is printed before returning.
Note: it is the consequence of the tests on the present character that determines whether the next character is to be printed in 'K' or 'L' mode. Also note how the program does not cater for ':' in REM statements.