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| documentations:basic_keywords [2015/02/28 18:08] – external edit 127.0.0.1 | documentations:basic_keywords [2015/03/14 09:04] – [Lines] pulkomandy | ||
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| + | ====== BASIC file format ====== | ||
| + | |||
| + | ===== Header ===== | ||
| + | |||
| + | BASIC sources aren't stored in plain ASCII. To allow faster loading and parsing, they are stored in bytecode format. The file is in standard DECB format, with a single block of type 0xFF. Since internal structures use absolute addresses, it is important to keep that header to know the loading address of the BASIC program. | ||
| + | |||
| + | ^Offset^Description^ | ||
| + | |0|File type = 0xFF| | ||
| + | |1|File size| | ||
| + | |3|Load address| | ||
| + | |||
| + | ===== Lines ===== | ||
| + | |||
| + | A BASIC program is a packed linked list of program lines. | ||
| + | |||
| + | ^Offset^Description^ | ||
| + | |0|Address of next line| | ||
| + | |2|Line number in hex| | ||
| + | |4|NULL-terminated line data| | ||
| + | |||
| + | The end of the listing is marked with a NULL next line pointer. | ||
| + | |||
| + | The line data is a mix of tokens and ASCII characters. The tokens are used to encode all the keywords and functions, but everything else (numbers, strings, comments) is stored in ASCII. | ||
| + | ====== Keyword and token list ====== | ||
| + | |||
| ^Keyword^Description^ | ^Keyword^Description^ | ||
| |''?'' | |''?'' | ||
