Tandy 200 BASIC tokenized file

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By default on the Tandy 200, the first token of the first line of the BASIC program in RAM is at address 0xA001. For all other Model T computers, including the Model 100, the first token is at 0x8001.
 
By default on the Tandy 200, the first token of the first line of the BASIC program in RAM is at address 0xA001. For all other Model T computers, including the Model 100, the first token is at 0x8001.
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Latest revision as of 04:19, 18 July 2024

File Format
Name Tandy 200 BASIC tokenized file
Ontology
Extension(s) .ba
Released 1983

Tandy 200 BASIC was a version of Microsoft BASIC for the Radio Shack Tandy 200 computer. The tokenizations for the TRS-80 Model 100 and Tandy 102 appear to be identical. In fact, while the research that created this page was done on a Tandy 200, experiments using emulated systems indicate that the tokenized BASIC file format is the same across most of the computers related to the Kyocera Kyotronic-85, with the exception being the models made by NEC.

Which of the Kyotronic-85 Sisters use this format
Computer Model Uses Tandy 200 Tokenization?
Kyocera Kyotronic-85
Olivetti M10
TRS-80 Model 100
Tandy 200
Tandy 102		 Yes
NEC PC-8201
NEC PC-8201A
NEC PC-8300 		No

While the NEC PC-8201/8300 format is not the same, the BASIC it runs (N82 BASIC) is very close and it is expected the tokenization will be similar.

Contents

[edit] Tokens

All BASIC tokens on the Tandy 200 are a single byte with a value from 128 to 255.

Table mapping token values to BASIC keywords
Hex Dec Keyword Notes
80 128 END
81 129 FOR
82 130 NEXT
83 131 DATA
84 132 INPUT
85 133 DIM
86 134 READ
87 135 LET
88 136 GOTO
89 137 RUN
8A 138 IF
8B 139 RESTORE
8C 140 GOSUB
8D 141 RETURN
8E 142 REM
8F 143 STOP
90 144 WIDTH
91 145 ELSE When tokenizing, the Tandy 200 always adds a colon (':') before the ELSE token (3A 91). If the user actually writes :ELSE it is tokenized as 3A 3A 91.
92 146 LINE
93 147 EDIT
94 148 ERROR
95 149 RESUME
96 150 OUT
97 151 ON
98 152 DSKO$
99 153 OPEN
9A 154 CLOSE
9B 155 LOAD Note that LOADM is simply the token for LOAD followed by an ASCII 'M'.
9C 156 MERGE
9D 157 FILES
9E 158 SAVE
9F 159 LFILES
A0 160 LPRINT
A1 161 DEF
A2 162 POKE
A3 163 PRINT
A4 164 CONT
A5 165 LIST
A6 166 LLIST
A7 167 CLEAR
A8 168 CLOAD
A9 169 CSAVE
AA 170 TIME$
AB 171 DATE$
AC 172 DAY$
AD 173 COM
AE 174 MDM
AF 175 KEY
B0 176 CLS
B1 177 BEEP
B2 178 SOUND
B3 179 LCOPY
B4 180 PSET
B5 181 PRESET
B6 182 MOTOR
B7 183 MAX
B8 184 POWER
B9 185 CALL
BA 186 MENU
BB 187 IPL
BC 188 NAME
BD 189 KILL
BE 190 SCREEN
BF 191 NEW
C0 192 TAB(
C1 193 TO
C2 194 USING
C3 195 VARPTR
C4 196 ERL
C5 197 ERR
C6 198 STRING$
C7 199 INSTR
C8 200 DSKI$
C9 201 INKEY$
CA 202 CSRLIN
CB 203 OFF
CC 204 HIMEM
CD 205 THEN
CE 206 NOT
CF 207 STEP
D0 208 +
D1 209 -
D2 210 *
D3 211 /
D4 212 ^
D5 213 AND
D6 214 OR
D7 215 XOR
D8 216 EQV
D9 217 IMP
DA 218 MOD
DB 219 \
DC 220 >
DD 221 =
DE 222 <
DF 223 SGN
E0 224 INT
E1 225 ABS
E2 226 FRE
E3 227 INP
E4 228 LPOS
E5 229 POS
E6 230 SQR
E7 231 RND
E8 232 LOG
E9 233 EXP
EA 234 COS
EB 235 SIN
EC 236 TAN
ED 237 ATN
EE 238 PEEK
EF 239 EOF
F0 240 LOC
F1 241 LOF
F2 242 CINT
F3 243 CSNG
F4 244 CDBL
F5 245 FIX
F6 246 LEN
F7 247 STR$
F8 248 VAL
F9 249 ASC
FA 250 CHR$
FB 251 SPACE$
FC 252 LEFT$
FD 253 RIGHT$
FE 254 MID$
FF 255 ' (QUOTE) When tokenizing, the single quote character expands to three characters: a colon (3A), the byte for REM (8E), and then FF.

[edit] File Format

Tokenised BASIC code is a sequence of tokenized lines. Each tokenized line has the following format:


Format of a single tokenized line
Name Length Description
PL PH 2 bytes Address in RAM of the next line of BASIC; unsigned 16-bit integer, little-endian. In a file, PL PH is merely a placeholder and the value is never used. In RAM, PL PH == 0 marks the end of the tokenized BASIC listing. (See #Details for PL PH.)
LL LH 2 bytes Line number; unsigned 16-bit integer, little-endian.
B0 … Bn Any number of bytes Depending on the high bit, each byte is either a token or an ASCII character.
NULL 1 byte NULL byte (0x00) to signal end of line.

Typically, the list of tokenized lines continues until the end of the file. Once a program is loaded into RAM, the end is signaled by two consecutive NULLs in the location where PL PH would normally start the next line.

[edit] Limits

  • Line numbers can range from 0 to 65529 (but see variances below).
  • Tokenized line length is limited to 256 characters, including the trailing NULL byte. (To do: double check this.)

[edit] Acceptable variances

While Tandy BASIC will never generate such files, it has no problem loading a tokenized program that:

  • Has line numbers out of order; the numerical value of a line number is ignored. Program lines are always LISTed and RUN in the order they appear in the tokenized file.
  • Contains duplicate line numbers; all lines are kept and run in the order found in the file. (GOTO is complicated as search starts at the next line, not the beginning of the program.)
  • Contains a line with zero bytes of data; LIST will show the line number with no text afterward. Does not replace or delete a preexisting line with that number.
  • Contains arbitrary bytes for PL PH; the value of PL PH is always recalculated at LOAD time.
  • Contains line numbers greater than the nominal maximum of 65529; this can be used to store hidden binary data according to John R. Hogerhuis.

Sidenote: while these variances are accepted by actual hardware, emulators may not be able to handle such files. For example, Virtual T (as of version 1.7 in 2022) refuses to load tokenized BASIC programs that have lines out of order, duplicate lines, or bogus values for PL PH.

[edit] Details for PL PH

In a file, the specific values of the 16-bit integer PL PH addresses are artifacts of where the file happened to be in memory before saving. The file's values are never used as Tandy BASIC always recalculates PL PH upon loading a program into RAM.

Although not technically part of the file format, one may want to calculate PL PH for compatibility with broken or persnickety emulators. Expand the section below to see details.

[edit] Calculating PL PH

Once in RAM, PL PH represents the absolute memory address of the next line. According to John Hogerhuis, PL PH is positioned before the line's data so the BASIC interpreter can quickly skip ahead to reach the target line of GOTO, GOSUB, THEN, ELSE, RESTORE, RESUME, RUN, LIST, LLIST, or EDIT.[note 1]) Additionally, the end of a tokenized BASIC listing is marked by the final line's PL PH equal to zero (two NULL bytes).

Note that because the addresses are absolute, not relative, their values depend not only on the program code but on an initial offset. That offset is why identical programs may not have identical checksums (but see the bacmp program).

By default on the Tandy 200, the first token of the first line of the BASIC program in RAM is at address 0xA001. For all other Model T computers, including the Model 100, the first token is at 0x8001.

  1. ↑ Searching begins at the next line in the program. The claim that one can speed up commonly used subroutines by putting them at low numbered lines is plausible as the search would detect immediately that the next line's number was too high and restart the search from the beginning.

[edit] Format documentation

[edit] Other links

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