Difference between revisions of "AMSDOS Header"
From CPCWiki - THE Amstrad CPC encyclopedia!
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Byte 24 and 25: file length LSB first | Byte 24 and 25: file length LSB first | ||
Byte 26 and 27: execution address for machine code program LSB first | Byte 26 and 27: execution address for machine code program LSB first | ||
| − | Byte 64 and 66: 24 bits file length LSB first | + | Byte 64 and 66: 24 bits file length LSB first. Just a copy, not used! |
Byte 67 and 68: checksum for bytes 00-66 stored LSB first | Byte 67 and 68: checksum for bytes 00-66 stored LSB first | ||
Byte 69 to 127: undefined content, free to use | Byte 69 to 127: undefined content, free to use | ||
| Line 19: | Line 19: | ||
This is only a summary. All details are in [[Firmware Guide]] chapter 9, page 4. | This is only a summary. All details are in [[Firmware Guide]] chapter 9, page 4. | ||
| − | [[Category: | + | [[Category:Disc Operating System]] |
| + | [[Category:Programming]] | ||
Revision as of 11:56, 20 December 2017
In AMSDOS it is possible to store files in two ways: headerless and with a header. Headerless files are often files which were created with OPENOUT and SAVE"filename",a. Programs normally have a file header, which consist of 128 bytes and contain the following data:
Byte 00: User number (value from 0 to 15 or #E5 for deleted entries) Byte 01 to 08: filename (fill unused char with spaces) Byte 09 to 11: Extension (fill unused char with spaces) Byte 16: first block (tape only) Byte 17: first block (tape only) Byte 18: file type (0:basic 1:protected 2:binary) Byte 21 and 22: loading address LSB first Byte 23: first block (tape only?) Byte 24 and 25: file length LSB first Byte 26 and 27: execution address for machine code program LSB first Byte 64 and 66: 24 bits file length LSB first. Just a copy, not used! Byte 67 and 68: checksum for bytes 00-66 stored LSB first Byte 69 to 127: undefined content, free to use
To calculate the checksum just add all bytes from 00 up to and including byte 66 together.
This is only a summary. All details are in Firmware Guide chapter 9, page 4.
