DISKDEFS(5) File formats DISKDEFS(5) NAME diskdefs - CP/M disk and file system format definitions DESCRIPTION The diskdefs file contains CP/M format descriptions, because CP/M in gen- eral does not store those in the file system and there are no standards of any kind. A diskdefs file consists of one or more entries of the format: diskdef name seclen size tracks count sectrk count blocksize size maxdir count [dirblks count] boottrk number [bootsec number] [skew number] [skewtab sector[,sector]...] [os 2.2|3|isx|p2dos|zsys] [offset size] [logicalextents count] [extentsize size] [libdsk:format name] end skew and skewtab must only be used exclusively. Comments are marked with a leading hash or semicolon and extend to the end of the line. It is possible to reserve space after the directory beyond maxdir using an inflated DPB ALV0. If the format makes use of that, dirblks must be set. bootsec contains the total number of sectors used by the boot area. This is for CP/M systems that map multiple logical tracks onto a physical track. While raw disk images can be configured for doing the same, accessing libdsk images needs to be done by physical tracks. The extentsize only needs to be set for systems that have been patches to use extents less than 16384 bytes, which unaltered CP/M does not allow, e.g. 320 blocks of 1024 bytes, which results in 16-bit block numbers and 8 blocks per extent. SEE ALSO cpm(5) CP/M tools March 15, 2026 DISKDEFS(5)
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