APF Imagination Machine BASIC tokenized file
The APF Imagination Machine was a late-1970s home computer platform. It was actually a game console with an add-on available to turn it into a full-fledged computer, with keyboard and tape drive. A floppy disk drive was also available. As with most computers of the time, it came with a version of the BASIC programming language built in.
APF BASIC programs were stored in a tokenized format. Byte values with the high bit set (#128-#255) were used to store tokens, with "high bit clear" values (#0-#127) used for literal ASCII characters.
BASIC lines were separated by the carriage return (hex 0D). In memory and perhaps on tape, they started with a two-byte address of the next program line in memory (big-endian, unlike the little-endian format used for addresses in most other personal computers); this part was apparently skipped in the disk format. The next two bytes contained the line number; unlike most other BASICs which used binary integers for this, APF BASIC used packed BCD code, where each "nybble" (half-byte) stood for one decimal digit. (Basically, if you read the hexadecimal dump of the bytes, interpret it as a decimal number with 0-9 standing for those digits and A-F never used.) Then the tokenized commands and literal characters of the program line followed.
Contents |
Tokens
Blank values indicate either that the token is unused or is used for something unknown. The manual shows both RND and LEN assigned to position 176 (decimal), apparently a misprint; 172 is skipped there, and is probably actually one of these.
| Hex | Dec | Token meaning |
|---|---|---|
| 80 | 128 | GOSUB |
| 81 | 129 | LET |
| 82 | 130 | DATA |
| 83 | 131 | INPUT |
| 84 | 132 | DIM |
| 85 | 133 | FOR |
| 86 | 134 | RETURN |
| 87 | 135 | THEN |
| 88 | 136 | ON |
| 89 | 137 | GOTO |
| 8A | 138 | TO |
| 8B | 139 | RESTORE |
| 8C | 140 | IF |
| 8D | 141 | STEP |
| 8E | 142 | STOP |
| 8F | 143 | READ |
| 90 | 144 | NEXT |
| 91 | 145 | |
| 92 | 146 | END |
| 93 | 147 | LIST |
| 94 | 148 | REM |
| 95 | 149 | USING |
| 96 | 150 | CSAVE |
| 97 | 151 | CLOAD |
| 98 | 152 | POKE |
| 99 | 153 | PLOT |
| 9A | 154 | HLIN |
| 9B | 155 | VLIN |
| 9C | 156 | COLOR |
| 9D | 157 | SHAPE |
| 9E | 158 | EDIT |
| 9F | 159 | SAVE |
| A0 | 160 | INIT |
| A1 | 161 | RUN |
| A2 | 162 | OPEN |
| A3 | 163 | CLOSE |
| A4 | 164 | MUSIC |
| A5 | 165 | CALL |
| A6 | 166 | DIR |
| A7 | 167 | TAB |
| A8 | 168 | SPC |
| A9 | 169 | INT |
| AA | 170 | ABS |
| AB | 171 | SGN |
| AC | 172 | RND or LEN? |
| AD | 173 | PEEK |
| AE | 174 | CHR$ |
| AF | 175 | ASC |
| B0 | 176 | RND or LEN? |
| B1 | 177 | KEY$ |
