GW-BASIC tokenized file

File Format
Name	GW-BASIC tokenized file
Ontology	Electronic File Formats Source code Tokenized BASIC GW-BASIC tokenized file
Extension(s)	.bas
Released	1981

GW-BASIC tokenized files stored programs in the version of the BASIC programming language used on IBM PC compatibles in the days when interpreted BASIC was regularly included on personal computers as shipped from the factory. Originally the IBM PC had versions of BASIC called BASIC and BASICA, the latter being an "advanced" BASIC with a few more features. Part of it was in ROM, and part was loaded from disk. Other manufacturers' PC compatibles (or "clones") didn't have the ROM BASIC, but used a BASIC from Microsoft which was compatible to it, and went by a few manufacturer-specific names but was generically known as GW-BASIC (with varying claims existing about what the GW stands for, either the initials of a Microsoft employee (Greg Whitten) involved in adapting it from Bill Gates' original CP/M BASIC, or possibly for "Gee Whiz").

Like most BASICs of its era, BASIC/BASICA/GW-BASIC used a tokenized format to save its programs, rather than plain-text source code. Printable ASCII characters (space through tilde) generally stood for themselves (except when part of a multi-byte sequence), but other bytes had different meanings. The "high-bit" bytes from #128-#255 stood for the various BASIC commands (some as single bytes, others as part of two-byte sequences), while some of the control characters had special meanings including signifying the start of a binary-encoded sequence encapsulating a numeric constant. A null (#0) byte marked the end of a program line, and some header bytes were used at the start of the line to encode the line number and some byte offsets.

Tokens

Blanks are unused, or at least unknown.

As noted, some of the tokens are preceded or followed by other bytes representing other symbols which are suppressed on listing the program (so they are "invisible"). These are presumably there to make parsing by the interpreter easier.

Hex	Dec	Token meaning
80	128
81	129	END
82	130	FOR
83	131	NEXT
84	132	DATA
85	133	INPUT
86	134	DIM
87	135	READ
88	136	LET
89	137	GOTO
8A	138	RUN
8B	139	IF
8C	140	RESTORE
8D	141	GOSUB
8E	142	RETURN
8F	143	REM
90	144	STOP
91	145	PRINT
92	146	CLEAR
93	147	LIST
94	148	NEW
95	149	ON
96	150	WAIT
97	151	DEF
98	152	POKE
99	153	CONT
9A	154
9B	155
9C	156	OUT
9D	157	LPRINT
9E	158	LLIST
9F	159
A0	160	WIDTH
A1	161	ELSE (stored with invisible colon, 3A, before it)
A2	162	TRON
A3	163	TROFF
A4	164	SWAP
A5	165	ERASE
A6	166	EDIT
A7	167	ERROR
A8	168	RESUME
A9	169	DELETE
AA	170	AUTO
AB	171	RENUM
AC	172	DEFSTR
AD	173	DEFINT
AE	174	DEFSNG
AF	175	DEFDBL
B0	176	LINE
B1	177	WHILE (stored with invisible plus, E9, after it)
B2	178	WEND
B3	179	CALL
B4	180
B5	181
B6	182
B7	183	WRITE
B8	184	OPTION
B9	185	RANDOMIZE
BA	186	OPEN
BB	187	CLOSE
BC	188	LOAD
BD	189	MERGE
BE	190	SAVE
BF	191	COLOR
C0	192	CLS
C1	193	MOTOR
C2	194	BSAVE
C3	195	BLOAD
C4	196	SOUND
C5	197	BEEP
C6	198	PSET
C7	199	PRESET
C8	200	SCREEM
C9	201	KEY
CA	202	LOCATE
CB	203
CC	204	TO
CD	205	THEN
CE	206	TAB(
CF	207	STEP
D0	208	USR
D1	209	FN
D2	210	SPC(
D3	211	NOT
D4	212	ERL
D5	213	ERR
D6	214	STRING$
D7	215	USING
D8	216	INSTR
D9	217	' (stored with invisible ":REM", 3A 8F, before it)
DA	218	VARPTR
DB	219	CSRLIN
DC	220	POINT
DD	221	OFF
DE	222	INKEY$
DF	223
E0	224
E1	225
E2	226
E3	227
E4	228
E5	229
E6	230	>
E7	231	=
E8	232	<
E9	233	+
EA	234	-
EB	235	*
EC	236	/
ED	237	^
EE	238	AND
EF	239	OR
E0	240	XOR
F1	241	EQV
F2	242	IMP
F3	243	MOD
F4	244	\
F5	245
F6	246
F7	247
F8	248
F9	249
FA	250
FB	251
FC	252
FD	253	(signals that next byte represents token from List 2)
FE	254	(signals that next byte represents token from List 3)
FF	255	(signals that next byte represents token from List 4)

List 2: 2nd-byte tokens following FD

These are preceded by a FD (hex) byte.

Hex	Dec	Token meaning
81	129	CVI
82	130	CVS
83	131	CVD
84	132	MKI$
85	133	MKS$
86	134	MKD$
87	135
88	136
89	137
8A	138
8B	139	EXTERR

List 3: 2nd-byte tokens following FE

These are preceded by a FE (hex) byte.

Hex	Dec	Token meaning
81	129	FILES
82	130	FIELD
83	131	SYSTEM
84	132	NAME
85	133	LSET
86	134	RSET
87	135	KILL
88	136	PUT
89	137	GET
8A	138	RESET
8B	139	COMMON
8C	140	CHAIN
8D	141	DATE$
8E	142	TIME$
8F	143	PAINT
90	144	COM
91	145	CIRCLE
92	146	DRAW
93	147	PLAY
94	148	TIMER
95	149	ERDEV
96	150	IOCTL
97	151	CHDIR
98	152	MKDIR
99	153	RMDIR
9A	154	SHELL
9B	155	ENVIRON
9C	156	VIEW
9D	157	WINDOW
9E	158	PMAP
9F	159	PALETTE
A0	160	LCOPY
A1	161	CALLS
A2	162
A3	163
A4	164	NOISE (PCjr), DEBUG (Sperry PC)
A5	165	PCOPY (PCjr, EGA system)
A6	166	TERM (PCjr)
A7	167	LOCK
A8	168	UNLOCK

List 4: 2nd-byte tokens following FF

These are preceded by a FF (hex) byte.

Hex	Dec	Token meaning
81	129	LEFT$
82	130	RIGHT$
83	131	MID$
84	132	SGN
85	133	INT
86	134	ABS
87	135	SQR
88	136	RND
89	137	SIN
8A	138	LOG
8B	139	EXP
8C	140	COS
8D	141	TAN
8E	142	ATN
8F	143	FRE
90	144	INP
91	145	POS
92	146	LEN
93	147	STR$
94	148	VAL
95	149	ASC
96	150	CHR$
97	151	PEEK
98	152	SPACE$
99	153	OCT$
9A	154	HEX$
9B	155	LPOS
9C	156	CINT
9D	157	CSNG
9E	158	CDBL
9F	159	FIX
A0	160	PEN
A1	161	STICK
A2	162	STRIG
A3	163	EOF
A4	164	LOC
A5	165	LOF

Format documentation

• GW-BASIC tokenised program format

Sample files

• Many files on Between Heaven and Hell Version II CD, such as /200/104/*.bas

Other links and references

• Wikipedia article: GW-BASIC