System Variables

Status/width	Address	Mnemonic	Description
X2	$5B52	OLDHL	Temporary register store while switching ROMs.
X2	$5B54	OLDBC	Temporary register store while switching ROMs.
X2	$5B56	OLDAF	Temporary register store while switching ROMs.
N2	$5B58	TARGET	Subroutine address in ROM 3.
X2	$5B5A	RETADDR	Return address in ROM 1.
X1	$5B5C	BANKM	Copy of last byte output to Memory Paging Control ($7FFD / 32765). This byte must be kept up to date with the last value output to the port if interrupts are enabled.
X1	$5B5D	RAMRST	RST 8 instruction. Used by ROM 1 to report old errors to ROM 3.
N1	$5B5E	RAMERR	Error number passed from ROM 1 to ROM 3. Also used by SAVE/LOAD as temporary drive store.
2	$5B5F	BAUD	RS232 bit period in T states/26. Set by FORMAT LINE.
N2	$5B61	SERFL	Second-character-received-flag, and data.
N1	$5B63	COL	Current column from 1 to WIDTH.
1	$5B64	WIDTH	Paper column width. Defaults to 80.
1	$5B65	TVPARS	Number of inline parameters expected by RS232.
1	$5B66	FLAGS3	Various flags. Bits 0, 1, 6 and 7 unlikely to be useful. Bit 2 is set when tokens are to be expanded on printing. Bit 3 is set if print output is RS232. The default (at reset) is Centronics. Bit 4 is set if a disk interface is present. Bit 5 is set if drive B: is present.
X1	$5B67	BANK678	Copy of last byte output to Plus 3 Memory Paging Control ($1FFD / 8189). This byte must be kept up to date with the last value output to the port if interrupts are enabled.
*N1	$5B68	FLAGN	Flags for the NextOS system.
*N1	$5B69	MAXBNK	Maxmium available RAM bank number.
X2	$5B6A	OLDSP	Old SP (stack pointer) when TSTACK is in use.
X2	$5B6C	SYNRET	Return address for ONERR.
5	$5B6E	LASTV	Last value printed by calculator.
*1	$5B73	TILEBNKL	Tiles bank for Lores.
*1	$5B74	TILEML	Tilemap bank for Lores.
*1	$5B75	TILEBNK2	Tiles bank for layer2.
*X1	$5B77	NXTBNK	Bank containing NXTLIN.
*1	$5B78	DATABNK	Bank containing DATADD.
1	$5B79	LODDRV	Holds 'T' if LOAD, VERIFY, MERGE are from tape, otherwise holds 'A', 'B' or 'M'.
1	$5B7A	SAVDRV	Holds 'T' if SAVE is to tape, otherwise holds 'A', 'B' or 'M'.
1	$5B7B	L2SOFT	Soft copy of Layer 2 Access Port ($123B / 4667)
2	$5B7C	TILEWL	Width of lo-res tilemap
2	$5B7E	TILEW2	Width of layer2 tilemap
2	5B80H	TILEOFFL	Offset in bank for lo-res tilemap
2	$5B82	TILEOFF2	Offset in bank for layer2 tilemap
2	$5B84	COORDSL	x,y coords of last point plotted (lo-res)
2	$5B86	COORDS2	x,y coords of last point (layer 2)
2	$5B88	COORDSULA	x,y coords of last point (standard)
2	$5B8A	COORDSHR	x,y coords of last point (hi-res)
2	$5B8C	COORDSHC	x,y coords of last point (hi-colour)
1	$5B8E	INKL	INK colour for lo-res mode
1	$5B8F	INK2	INK colour for layer2 mode
1	5B90H	ATTRULA	Attributes for standard mode
1	$5B91	INKHR	INK colour for hi-res mode
1	$5B92	ATTRHC	Attributes for hi-colour mode
1	$5B93	INKMASK	Softcopy of Enhanced ULA Ink Color Mask ($42) (or 0)
N8	$5B94	STRIP1	Stripe one bitmap
N8	$5B9C	STRIP2	Stripe two bitmap
X91	$5BFF	TSTACK	Temporary stack grows down from here. Used when RAM page 7 is switched in at top of memory (while executing the editor or calling +3DOS). It may safely go down to $5B9D (and across STRIP1 and STRIP2 if necessary).
N8	$5C00	KSTATE	Used in reading the keyboard.
N1	$5C08	LASTK	Stores newly pressed key.
1	$5C09	REPDEL	Time (in 50ths of a second) that a key must be held down before it repeats.
1	$5C0A	REPPER	Delay (in 50ths of a second) between successive repeats of a key held downs.
N2	$5C0B	DEFADD	Address of arguments of user defined function (if one is being evaluated), otherwise 0.
Nl	$5C0D	K DATA	Stores 2nd byte of colour controls entered from keyboard.
N1	$5C0E	TVDATA	Stores bytes of colour, AT and TAB controls going to TV.
X38	$5C10	STRMS	Addresses of channels attached to streams.
2	$5C36	CHARS	256 less than address of character set (which starts with space and carries on to (C)). Normally in ROM, but you can set up your down in RAM and make CHARS point to it.
1	$5C38	RASP	Length of warning buzz.
1	$5C39	PIP	Length of keyboard click.
1	$5C3A	ERRNR	1 less than the report code. Starts off at 255 (for -1) so 'PEEK 23610' gives 255.
X1	$5C3B	FLAGS	Various flags to control the BASIC system.
X1	$5C3C	TVFLAG	Flags associated with the TV.
X2	$5C3D	ERRSP	Address of item on machine stack to be used as error return.
N2	$5C3F	LISTSP	Address of return address from automatic listing.
N1	$5C41	MODE	Specifies 'K', 'L', 'C', 'E' or 'G' cursor.
2	$5C42	NEWPPC	Line to be jumped to.
1	$5C44	NSPPC	Statement number in line to be jumped to. Poking first NEWPPC and then NSPPC forces a jump to a specified statement in a line.
2	$5C45	PPC	Line number of statement currently being executed.
1	$5C47	SUBPPC	Number within line of statement currently being executed.
1	$5C48	BORDCR	Border colour multiplied by 8; also contains the attributes normally used for the lower half of the screen.
2	$5C49	E PPC	Number of current line (with program cursor).
X2	$5C4B	VARS	Address of variables.
N2	$5C4D	DEST	Address of variable in assignment.
X2	$5C4F	CHANS	Address of channel data.
X2	$5C51	CURCHL	Address of information currently being used for input and output.
X2	$5C53	PROG	Address of BASIC program.
X2	$5C57	NXTLIN	Address of next line in program.
X2	$5C57	DATADD	Address of terminator of last DATA item.
X2	$5C59	E LINE	Address of command being typed in.
2	$5C5B	K CUR	Address of cursor.
X2	$5C5D	CH ADD	Address of the next character to be interpreted - the character after the argument of PEEK, or the NEWLINE at the end of a POKE statement.
2	$5C5F	X PTR	Address of the character after the [] marker.
X2	$5C61	WORKSP	Address of temporary work space.
X2	$5C63	STKBOT	Address of bottom of calculator stack.
X2	$5C65	STKEND	Address of start of spare space.
N1	$5C67	BREG	Calculator's B register.
N2	$5C68	MEM	Address of area used for calculator's memory
1	$5C6A	FLAGS2	More flags. (Bit 3 set when CAPS SHIFT or CAPS LOCK is on.)
X1	$5C6B	DF SZ	The number of lines (including one blank line) in the lower part of the screen.
2	$5C6C	S TOP	The number of the top program line in automatic listings.
2	$5C6E	OLDPPC	Line number to which CONTINUE jumps.
1	$5C70	OSPPC	Number within line of statement to which CONTINUE jumps.
N1	$5C71	FLAGX	Various flags.
N2	$5C72	STRLEN	Length of string type destination in assignment.
N2	$5C74	T ADDR	Address of next item in syntax table (very unlikely to be useful).
2	$5C76	SEED	The seed for RND. This is the variable that is set by RANDOMIZE.
3	$5C78	FRAMES	3 byte (least significant byte first), frame counter incremented every 20ms.
2	$5C7B	UDG	Address of first user-defined graphic
1	$5C7D	COORDS	X-coordinate of last point plotted.
1	$5C7E		Y-coordinate of last point plotted.
*1	$5C7F	GMODE	Graphical layer/mode flags.
X2	5C80h	PRCC	Full address of next position for LPRINT to print at (in ZX printer buffer). Legal values 5B00 - 5B1F.
2	$5C82	ECHO E	33-column number and 24-line number (in lower half) of end of input buffer.
2	$5C84	DF CC	Address in display file of PRINT position.
2	$5C86	DF CCL	Like DF CC for lower part of screen.
X1	$5C88	S POSN	33-column number for PRINT position.
X1	$5C89		24-line number for PRINT position.
X2	$5C8A	SPOSNL	Like S POSN for lower part.
1	$5C8C	SCR CT	Counts scrolls - it is always 1 more than the number of scrolls that will be done before stopping with 'scroll'?
1	$5C8D	ATTR P	Permanent current colours, etc., (as set up by colour statements).
1	$5C8E	MASK P	Used for transparent colours, etc. Any bit that is 1 shows that the corresponding attribute bit is taken not from ATTR P, but from what is already on the screen.
N1	$5C8F	ATTR T	Temporary current colours, etc., (as set up by colour items).
N1	5C90h	MASK T	Like MASK P, but temporary.
1	$5C91	P FLAG	More flags.
N30	$5C92	MEMBOT	Calculator's memory area - used to store numbers that cannot conveniently be put on the calculator stack.
2	$5CB0	NMIADD	Holds the address of the users NMI service routine.
2	$5CB2	RAMTOP	Address of last byte of BASIC system area.
2	$5CB4	P RAMT	Address of last byte of physical RAM.