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BASIC ROM Routines
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BASIC ROM Routines
by Christopher Dewhurst

BASIC IV ROM Routines
By Steve Fewell

I decided to begin something I've been wanting to do for a long time, that is to produce listings of BASIC 4 ROM's routines, together with detailed descriptions of how they work.

Please let me know what you think, and whether you'd like to see more like it. If anyone else wants to have a go at writing up with me then please feel free to post (added CJR: send them to 8BS) your own descriptions of routines from BASIC 4 (or another version of BASIC).

If I've made a mistake, and someone wants to correct/expand on something, then please do so.

Latest addtions:

03/Mar/2004 Addition of keywords: PROC, LOCAL, ENDPROC, FN, and routines Search Subroutine Name in Lookup Table, '=' Return from a Function call, Create lookup reference for Subroutine Name, Add subroutine name to FN/PROC variable lookup table, Call Subroutine, Load variable and push its value to the BASIC stack, Set Variable to value from the BASIC Stack,

19/Jan/2004 Addition of keywords: FOR, NEXT, ON, REPEAT and UNTIL

06/Jan/2004 Addition of the 'Get Line Number & find Program Address of the Line Number' routine and keywords: TRACE, GOSUB, RETURN, GOTO, RESTORE, READ and IF

28/Dec/2003 Greetings during this Christmas and new year period!
This update contains descriptions for the Trigonometry functions!
Addition of keywords: TAN, ACS, ASN, ATN, SIN and COS

05/Oct/2003 Addition of the 'BASIC error handler' routine and keywords: CHAIN, RUN, LOAD, END, CALL, DELETE, RENUMBER, AUTO, USR, EXT, =PTR, BGET, OPENIN, OPENOUT, OPENUP, EOF, INSTR, STRING$, CHR$, SAVE, OSCLI, CLOSE and BPUT

12/Sep/2003 Addition of "'[' - Begin Assembly", "Execute '*'-command", "Execute next command line / program statement", 'skip end of program line' and 'Display current Line Number to screen [for TRACE]' routines and keywords: OLD, EXT= and PTR=

20/Aug/2003 Addition of 'Print Line Number on screen', 'Calculate next Random Number Seed value', 'Output ASCII character/BASIC Token (in ASCII text)' routines and keywords: TIME=, TIME$=, MOVE, DRAW, PLOT, REPORT, VDU, RND, POS, VPOS, EVAL, INT, INKEY, INKEY$, SGN, POINT(, ADVAL, =TIME, =TIME$, LEFT$(, RIGHT$(, MID$(, EDIT, LIST, LISTO

01/Aug/2003 Addition of 'BASIC ROM Startup Initialisations', 'Find positon of Program Line', 'Tokenise command line text', 'Insert line into Program', 'Remove line from program', 'Check program can be read correctly' and 'Detokenise Line Number' routines and keywords HIMEM=, LOMEM=, PAGE=, CLEAR, GCOL, COLOUR and MODE

10/Jun/2003 Addition of 'Assemble Assembly Statement', 'Output character to screen' and 'Extract next field' routines and keywords PRINT, PRINT#, CLG, SOUND, ENVELOPE, WIDTH, INPUT and INPUT#

01/May/2003 Addition of Numeric to ASCII (NUMASC) routine and keywords: NOT, VAL, ASC, ABS, LEN, =PAGE, TOP, COUNT, =LOMEM, =HIMEM, ERL & ERR

09/Apr/2003 Addition of Disassembler program to the analysis disc images, Added LET & DIM keywords, and added &AD36 (get value routine)

24/Mar/2003 Addition of Reference Disk Images, SQR & routine [&9909] to evaluate Variables and Arrays (and get address of the required value/variable parameter block).

28/Feb/2003 First of the Floating-Point Series calculations for functions such as LOG, LN and EXP

BASIC IV Routines

Routine Name	Start Address	Address Range	Comments
BASIC ROM header	8000	8000-8022
BASIC ROM Startup Initialisations	802B	802B-8074
Lookup Subroutine Name in FN/PROC Variable Lookup Table	8075	8075-8084
Get Address of Variable	8085	8085-80CC
Search for Program Line	80CD	80CD-80F8
Integer Division	80F9	80F9-8171
Convert Integer to Floating-Point	8185	8185-81CB	Also includes: 81E0-81E1
Set FWA to 1-byte value	81D5	81D5-81DF
Normalise FWA#2	81E2	81E2-81F6	Also includes: 81CC-81D4
Normalise FWA#1	81F7	81F7-8241
Convert Floating-Point to Integer	8242	8242-826E	Also includes: 8272-8274; 827E-82BC; 82BD-82BF; 82C0-82C3
Integer Reverse Order Complement	82C4	82C4-82DF
Split FWA (into Integer/Fractional part)	82E0	82E0-830C	Also includes: 8275-827D
Calculate next Random Number Seed value	831E	831E-8348
Copy FWB to FWA	8349	8349-8367
Floating-point addition	8368	8368-8455
BASIC Keyword List	8456	8456-8768
BASIC Execution Address List	8769	8769-884C
'[' Begin Assembly	8920	891A-89D3
Assemble Assembly instruction/statement	89EB	89D4-8CD6	Also includes: 884D-891B
Replace untokenised ASCII value with a 1-byte token	8CEB	8CEB-8D03
Tokenise Line Number	8D04	8D04-8D83
Check for Variable name character or digit (in A)	8D84	8D84-8D9A
Increment [and read] pointer (&37, &38)	8DA0	8DA0-8DAE
Tokenise Command Line	8DB2	8DAF-8ED4	Also includes: 8D9B-8D9F
Next non-space Char PTRB	8ED5	8ED5-8EDF	Also includes: 8EEB-8EF0
Next non-space Char PTRA	8EE0	8EE0-8EEA	Also includes: 8CD7-8CEA
CHAIN	8EFB	8EFB-8EFF
OLD	8F00	8F00-8F11
RUN	8F12	8F12-8F1F
LOAD	8F20	8F20-8F24
END	8F25	8F25-8F2C
BASIC ROM Startup initialisations (part 2)	8F2D	8F2D-8F7C
NEW	8F7D	8F7D-8F82	Also includes: BEFE-BF13
Prompt for command line and execute the entered command(s)	8F83	8F83-8FA3
Execute '*'-Command	8FA4	8FA4-8FAD
Execute next command line / program statement	8FAE	8FAE-9049
LET	904A	904A-905F	Also includes: 9072-9085
'=' Return from a Function Call (FN)	9060	9060-9071
STOP	9086	9086-9088
Set String variable	90AB	90AB-9140	Also includes: BE25-BE32
PRINT#	9141	9141-918C	Also includes: BA3C-BA57
PRINT	918D	918D-9229	Also includes: 927A-9293
(PRINT) TAB(	9241	922A-925A	Also includes: 9840-9844
(PRINT) SPC	925B	925B-9266
(PRINT) quote (')	9267	9267-926E
Get Result of expression from BASIC Text pointer A & convert to Integer	926F	926D-9279
CALL	92BE	92BE-9313
DELETE	9317	9314-934C
RENUMBER	9384	934D-9488
AUTO	9489	9489-94B8
DIM	9534	9534-9604	Also includes: 94B9-9502, 9AF6-9B1B, BC43-BC50, BEEF-BEFD
HIMEM=	960F	960F-961F	Also includes: 96B9-96BD
LOMEM=	9620	9620-9633
PAGE=	9634	9634-963D
CLEAR	963E	963E-9645
TRACE	9646	9646-9678
TIME=	9679	9679-968D
TIME$=	968E	968E-96A3
Get Integer result of expression and check for closing bracket	96A7	96A7-96AB
Get Integer result of expression	96AF	96AC-96B3	Also includes: 8EF1-8EF5
Get Integer value at PTR B	96B4	96B4-96B8
Check if Integer and Convert if Float	96BE	96BE-96D9
Get & Check Float value	96DA	96D7-96E3
PROC	96E4	96E4-96FA
LOCAL	9703	96FB-9731
GCOL	9741	9741-9754
COLOUR	9755	9755-975E
MODE	975F	975F-97A1
MOVE	97A2	97A2-97A5
DRAW	97A6	97A6-97B0
PLOT	97B1	97B1-97DF
CLG	97E0	97E0-97E6
CLS	97E7	97E7-97F3
REPORT	97F4	97F4-9807
VDU	980D	9808-983F
Create Lookup Table reference for Subroutine Name	9845	9845-9853
Create new variable name in Variable Pointer table	9854	9854-9882
Allocate space for new variable	9883	9883-98AA
Evaluate variable name & Create if new variable	98AE	98AB-98BF
'?' and '!' address peek/poke operators	98D1	98D1-98DB
'$' address peek/poke operator	98DC	98DC-98EA
Evaluate Variable name and return value address	9909	9909-99AD	Also includes: 98C1-98D0
'!' and '?' address modifier operators	99AE	99AE-99D4
Get address of specified Array element	99FE	99FE-9AE9	Also includes: 9503-952B
Detokenise the requested Line Number and Set IWA to the Line Number value	9B1C	9B1C-9B45
Check for '=', evaluate expression & check end of statement	9B52	9B52-9B5F	Also includes: 9B8E-9B95
ENDPROC	9B9A	9B9A-9BA5
Check for End of Statement	9BA6	9BA6-9BCE	Also includes: 9B96-9B99
Check & skip end of program line	9BCF	9BCF-9C04
IF	9C08	9C05-9C4A
Display current Line number to screen [for TRACE]	9C4B	9C4B-9C64
Compare Float values	9C82	9C65-9CC5
Compare Integer values	9CC9	9CC6-9D01
Compare String values	9D02	9D02-9D2E
Expression Handler	9D3B	9D2F-9D4B	Also includes: 9D7B-9D88, 9DA9-9DB4, 9E4C-9E57, 9FC1-9FDA, A00F-A026
'OR' Operator	9D4C	9D4C-9D65
'EOR' Operator	9D66	9D66-9D7A
'AND' Operator	9D89	9D89-9DA8
'=' and other relational operators	9DB5	9DB5-9DCC
'<' Operator	9DCD	9DCD-9DE0
'<=' Operator	9DE1	9DE1-9DEB
'<>' Operator	9DEC	9DEC-9DF4
'>' Operator	9DF5	9DF5-9E06
'>=' Operator	9E07	9E07-9E0F
String Addition	9E22	9E22-9E4B
'+' Operator	9E58	9E58-9E64	Also includes: 9E91-9EBC
Integer Addition	9E65	9E65-9E90	Also includes: 9E4F-9E57
'-' Operator	9EBD	9EBD-9EC9	Also includes: 9EE7-9F11; ACC7-ACD6
Integer Subtraction	9ECA	9ECA-9EE6
'*' Operator	9F3B	9F12-9F63
Integer Multiplication	9F64	9F64-9FDA
'/' Operator	9FDB	9FDB-9FF4
Integer MOD routine	9FF5	9FF5-9FFC
Integer DIV routine	9FFD	9FFD-A00E
'^' Operator (raise to Power)	A027	A027-A07F
Print Line Number on screen	A085	A081-A0C9	Also includes: 8021-802A
Multiply FWA Mantissa by 10	A26C	A26C-A2BB
NUMASC (convert Numeric value to ASCII value)	A118	A0CA-A2D9	Also Includes:
ASCNUM: Extract Number at PTRB	A2E1	A2DA-A35C
ASCNUM: Handle Exponental values & complete number conversion	A35D	A35D-A3F1
Floating-point Sign	A3F2	A3F2-A40A
Copy FWA to FWB	A40B	A40B-A427
Floating-point multiply by 10	A436	A436-A477	Also Includes: A428-A435
Floating-point divide by 10	A478	A478-A4DF
Unpack FP Variable to FWB	A4E0	A4E0-A50C
Store FWA to Temporary Variable	A50D	A50D-A518
Pack FWA to Variable	A519	A519-A538
Unpack FP Variable to FWA	A541	A539-A56F
Clear FWB	A570	A570-A57E
TAN	A59B	A59B-A5BD
Raise FWA to the power of the integer value in A	A5BE	A5BE-A5E1
Floating-Point Reciple	A5E9	A5E9-A5ED	Also Includes: A589-A591
Floating-Point Division Entry Point	A5EE	A5EE-A5F9
Floating-Point Division	A5FA	A5FA-A689	Also includes: &A5E5 to &A5E8
Floating-Point Subtract Entry Point	A68A	A68A-A68C
Floating-Point Addition Entry Point	A68D	A68D-A694
Round FWA Mantissa to 4 bytes	A695	A695-A6A5	Also includes &A6AB to &A6B3.
Floating-Point Multiply Entry Point	A6A6	A6A6-A6AA
Clear FWA	A6B4	A6B4-A6C4
Floating-Point Multiplication	A6CF	A6CF-A745
LN	A746	A746-A7B4
SQR	A7B5	A7B5-A860
Evaluate continued-fraction expansions Series	A861	A861-A89B	Also includes: A57F-A588 and A592-A59A
ACS	A89C	A89C-A8A0
ASN	A8A1	A8A1-A8C2
ATN	A8C3	A8C3-A90C
SIN	A90D	A90D-A90D
COS	A90E	A90E-A9AC
RAD	A9C8	A9C8-A9CE
LOG	A9CF	A9CF-A9D7
DEG	A9D8	A9D8-A9DE
EXP	A9DF	A9DF-AA11
RND	AA73	AA1E-AA7F
Load Integer from Zero Page Address	AA80	AA80-AA92
NOT	AA93	AA93-AAA2
POS	AAA3	AAA3-AAA8
USR	AAA9	AAA9-AABB
VPOS	AABC	AABC-AAC4
EXT	AAC5	AAC5-AAC8
=PTR	AAC9	AAC9-AAD6
BGET	AAD7	AAD7-AADE
OPENIN	AADF	AADF-AAE2
OPENOUT	AAE3	AAE3-AAE6
OPENUP	AAE7	AAE7-AAFE
PI	AAFF	AAFF-AB04
EVAL	AB05	AB05-AB39
VAL	AB49	AB46-AB4D
Ascnum (ASCII String to Binary Number)	AB4E	AB4E-AB88	Also includes:AB3A-AB45
INT	AB8A	AB8A-ABB2	Also includes: 830D-831D
ASC	ABB3	ABB3-ABC1
INKEY	ABC2	ABC2-ABCB	Also includes: AA12-AA1D
EOF	ABCF	ABCF-ABDA
TRUE	ABDB	ABDB-ABDC
FALSE (Clear IWA)	ABE8	ABDD-ABEB
SGN	ABF5	ABEC-AC0D
POINT(	AC0E	AC0E-AC35
INSTR(	AC36	AC36-ACB3
ABS	ACB7	ACB4-ACBD	Also includes: ACC4-ACC6
Integer Positive	ACBE	ACBE-ACC3
Floating-Point Compliment	ACCA	ACCA-ACD6
Compliment Result	ACD7	ACD7-ACDD
Integer Compliment	ACDE	ACDE-ACF7
Extract next field	ACF8	ACF8-AD18
Extract String	AD19	AD11-AD35
Evaluate Variable/Value/BASIC Function/Open Bracket	AD36	AD36-AD8B
Evaluate expression and check for closing bracket	ADAC	ADAC-ADB6
Extract Hex Integer	ADB7	ADB7-ADEB
ADVAL	ADEC	ADEC-ADF8
TOP	ADF9	ADF9-AE07
=PAGE	AE08	AE08-AE0D
LEN	AE11	AE0E-AE17
IWA = 8-bit or 16-bit Integer	AE1A	AE18-AE24
COUNT	AE25	AE25-AE28
=LOMEM	AE29	AE29-AE2E
=HIMEM	AE2F	AE2F-AE34
ERL	AE35	AE35-AE3A
ERR	AE3B	AE3B-AE3E
GET	AE3F	AE3F-AE43
=TIME	AE44	AE44-AE56
=TIME$	AE57	AE57-AE68
GET$	AE69	AE69-AE72	Also includes: AE8F-AE93
LEFT$(	AE73	AE73-AE73
RIGHT$(	AE74	AE74-AEB2	Also includes: 96A4-96A6
INKEY$	AEB3	AEB3-AEBE
MID$(	AEC5	AEBF-AF1B
STR$	AF1C	AF1C-AF46
STRING$	AF47	AF47-AF82
Add subroutine name to FN/PROC variable lookup table	AF97	AF83-B00B
FN	B017	B017-B067
Call Subroutine	B068	B068-B180
Load Variable & Push its value to the BASIC Stack	B181	B181-B19F
Load Variable	B1A0	B1A0-B1A9
Load IWA with Integer from Address [iin]	B1AA	B1AA-B1C1
Load IWA with 1-byte Integer value	B1C2	B1C2-B1C6
Load FWA with Float Variable (ain)	B1C7	B1C7-B1F6
Load SWA with String Value	B1F7	B1F7-B22E
CHR$	B22F	B22F-B236
BASIC Error handler	B278	B237-B2A5
Reset ON ERROR code pointer	B2A6	B2A6-B2C7
SOUND	B2C8	B2C8-B2EB
ENVELOPE	B2EC	B2EC-B316
WIDTH	B317	B317-B324
Set Numeric variable	B32B	B325-B346	Also includes: B360-B388
Save Integer to Address	B347	B347-B35F
EDIT	B393	B389-B399
LIST	B39A	B39A-B3DC	Also: B3F3-B4F0
LISTO	B3DD	B3DD-B3F2
NEXT	B4F1	B4F1-B5F7
FOR	B618	B618-B6D8
GOSUB	B6D9	B6D9-B6F2
RETURN	B707	B707-B71C
GOTO	B71D	B71D-B738
ON	B75B	B739-B829
Get Line Number & find Program Address of the Line Number	B82A	B82A-B83B
INPUT#	B847	B83C-B8B1
INPUT	B8B6	B8B2-B94C	Also includes: 9299-92BD, BA70-BA91
RESTORE	B94D	B94D-B974
READ	B97D	B975-B9F0	Also includes: BA13-BA16
UNTIL	BA17	BA17-BA3B
REPEAT	BA58	BA58-BA6F
Start new output line	BA92	BA92-BA97
Remove Line Number (specified in the IWA) from the Program	BA98	BA98-BAEA
Tokenise Command Line and Insert Line into Program	BAEB	BAEB-BBAB
Initialise Page 7 & reset Variable pointers, etc...	BBAC	BBAC-BBE7	Also includes: BF14 to BF23
Pop Float from Stack (to &4A,&4B)	BBE8	BBE8-BBF9
Push FWA to Stack	BBFA	BBFA-BC21
Push Integer to BASIC Stack	BC26	BC22-BC42
Push String to Stack	BC51	BC51-BC69
Set Variable to value from the BASIC Stack	BC6A	BC6A-BCD1
Pop String from Stack	BCD2	BCD2-BCE5
Pop Integer from BASIC Stack	BCE6	BCE6-BD05
Pop Integer from BASIC Stack (Zp)	BD08	BD06-BD1D
Check for Stack clash with Heap	BD1E	BD1E-BD30	Also includes: BD34-BD36
Output ASCII character or BASIC Token (in ASCII text) to the screen	BD37	BD37-BD6B	Also includes: BD34-BD36
Output character to the screen	BD92	BD6C-BDC5	Also includes: BD31-BD36
Save Integer to Zero Page Address	BDC6	BDC6-BDD6
Load/Save named file	BDD7	BDD7-BDE4
Check Program can be read correctly	BDE5	BDE5-BE24	Also includes BECF-BEE1
Get Filename and set parameter block Filename and Load address	BE41	BE33-BE54
SAVE	BE55	BE55-BE86
OSCLI	BE87	BE87-BE92
EXT =	BE93	BE93-BE96
PTR =	BE97	BE97-BEAD
CLOSE	BEAE	BEAE-BEBC
BPUT	BEBD	BEBD-BECE
Read byte from I/O processor memory location (at the address contained in the IWA)	BEE2	BEE2-BEEE
Floating Point Constant Table	BF24	BF24-BFFA

Error Messages

Character Set

Memory Map

Glossary

Disassembly
8000 to 9000 HTML TEXT CSV
9000 to A000 HTML TEXT CSV
A000 to B000 HTML TEXT CSV
B000 to C000 HTML TEXT CSV

Reference Disc images

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03/Mar/2004	Addition of keywords: PROC, LOCAL, ENDPROC, FN, and routines Search Subroutine Name in Lookup Table, '=' Return from a Function call, Create lookup reference for Subroutine Name, Add subroutine name to FN/PROC variable lookup table, Call Subroutine, Load variable and push its value to the BASIC stack, Set Variable to value from the BASIC Stack,
19/Jan/2004	Addition of keywords: FOR, NEXT, ON, REPEAT and UNTIL
06/Jan/2004	Addition of the 'Get Line Number & find Program Address of the Line Number' routine and keywords: TRACE, GOSUB, RETURN, GOTO, RESTORE, READ and IF
28/Dec/2003	Greetings during this Christmas and new year period! This update contains descriptions for the Trigonometry functions! Addition of keywords: TAN, ACS, ASN, ATN, SIN and COS
05/Oct/2003	Addition of the 'BASIC error handler' routine and keywords: CHAIN, RUN, LOAD, END, CALL, DELETE, RENUMBER, AUTO, USR, EXT, =PTR, BGET, OPENIN, OPENOUT, OPENUP, EOF, INSTR, STRING$, CHR$, SAVE, OSCLI, CLOSE and BPUT
12/Sep/2003	Addition of "'[' - Begin Assembly", "Execute '*'-command", "Execute next command line / program statement", 'skip end of program line' and 'Display current Line Number to screen [for TRACE]' routines and keywords: OLD, EXT= and PTR=
20/Aug/2003	Addition of 'Print Line Number on screen', 'Calculate next Random Number Seed value', 'Output ASCII character/BASIC Token (in ASCII text)' routines and keywords: TIME=, TIME$=, MOVE, DRAW, PLOT, REPORT, VDU, RND, POS, VPOS, EVAL, INT, INKEY, INKEY$, SGN, POINT(, ADVAL, =TIME, =TIME$, LEFT$(, RIGHT$(, MID$(, EDIT, LIST, LISTO
01/Aug/2003	Addition of 'BASIC ROM Startup Initialisations', 'Find positon of Program Line', 'Tokenise command line text', 'Insert line into Program', 'Remove line from program', 'Check program can be read correctly' and 'Detokenise Line Number' routines and keywords HIMEM=, LOMEM=, PAGE=, CLEAR, GCOL, COLOUR and MODE
10/Jun/2003	Addition of 'Assemble Assembly Statement', 'Output character to screen' and 'Extract next field' routines and keywords PRINT, PRINT#, CLG, SOUND, ENVELOPE, WIDTH, INPUT and INPUT#
01/May/2003	Addition of Numeric to ASCII (NUMASC) routine and keywords: NOT, VAL, ASC, ABS, LEN, =PAGE, TOP, COUNT, =LOMEM, =HIMEM, ERL & ERR
09/Apr/2003	Addition of Disassembler program to the analysis disc images, Added LET & DIM keywords, and added &AD36 (get value routine)
24/Mar/2003	Addition of Reference Disk Images, SQR & routine [&9909] to evaluate Variables and Arrays (and get address of the required value/variable parameter block).
28/Feb/2003	First of the Floating-Point Series calculations for functions such as LOG, LN and EXP