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$ |
See also
- APF Imagination Machine data cassette
- APF Imagination Machine floppy disk
- APF Imagination Machine disk file system