h6. [[FileCore]] h6(. » [[FileCore Technical Details|Technical Details]] h6((. » FileCore Disc Descriptor h2. FileCore Disc Descriptor h4(#disc_descriptor_small). File Disc Descriptor (small Disc[1]) |_<^{width:4em}. Offset|_<^{width:8em}. Name|_<^. Meaning| |>^. +0|<^. _Log2Secsize_|<^. Log2 of sector size (Sector size = 2^x)| |>^. +1|<^. _Secspertrack_|<^. Number of sectors per track| |>^. +2|<^. _Heads_|<^. Number of disc heads, if interleaved otherwise -1 (1 for old directories)| |>^. +3|<^. _Density_|<^. "Disc density":#disc_densities| |>^. +4|<^. _IDlen_|<^. Length of id field of a map fragment (in bits)| |>^. +5|<^. _Log2Bpmp_|<^. Log2 of number of bytes per map bits| |>^. +6|<^. _Skew_|<^. Track to track sector skew for random access file allocation| |>^. +7|<^. _Bootoption_|<^. Boot option (as in [[*Opt 4]],n)| |>^. +8|<^. _Lowsector_|<^. Lowest numbered sector + "disc description flags":#disc_description| |>^. +9|<^. _Nzones_|<^. Number of zones in the map| |>^. +A-B|<^. __Zone_Spare__|<^. Number of non-allocation bits between zones| |>^. +C-F|<^. _Root_|<^. Disc address of root directory| |>^. +10-13|<^. __Disc_Size__|<^. Disc size in bytes| |>^. +14-15|<^. __Disc_Id__|<^. [[Disc Cycle ID|Disc cycle ID]]| |>^. +16-1F|<^. __Disc_Name__|<^. Disc name (spaced to 10 chars, no terminator)| |>^. +20-23|<^. _Disctype_|<^. [[File Types|Filetype given to disc]]| |>^. +24-3F|<^. |<^. Reserved, must be 0| h4(#disc_descriptor_large). File Disc Descriptor (Large Disc[2]) |_<^{width:4em}. Offset|_<^{width:8em}. Name|_<^. Meaning| |>^. +0|<^. _Log2Secsize_|<^. Log2 of sector size (Sector size = 2^x)| |>^. +1|<^. _Secspertrack_|<^. Number of sectors per track| |>^. +2|<^. _Heads_|<^. Number of disc heads, if interleaved otherwise -1 (1 for old directories)| |>^. +3|<^. _Density_|<^. "Disc density":#disc_densities| |>^. +4|<^. _IDlen_|<^. Length of id field of a map fragment (in bits)| |>^. +5|<^. _Log2Bpmp_|<^. Log2 of number of bytes per map bits| |>^. +6|<^. _Skew_|<^. Track to track sector skew for random access file allocation| |>^. +7|<^. _Bootoption_|<^. Boot option (as in [[*Opt 4]],n)| |>^. +8|<^. _Lowsector_|<^. Lowest numbered sector + "disc description flags":#disc_description| |>^. +9|<^. _Nzones_|<^. Number of zones in the map| |>^. +A-B|<^. __Zone_Spare__|<^. Number of non-allocation bits between zones| |>^. +C-F|<^. _Root_|<^. Disc address of root directory| |>^. +10-13|<^. __Disc_Size__|<^. Disc size in bytes| |>^. +14-15|<^. __Disc_Id__|<^. [[Disc Cycle ID|Disc cycle ID]]| |>^. +16-1F|<^. __Disc_Name__|<^. Disc name (spaced to 10 chars, no terminator)| |>^. +20-23|<^. _Disctype_|<^. [[File Types|Filetype given to disc]]| |>^. +24-27|<^. __Disc_size2__|<^. High word of disc size| |>^. +28|<^. __Share_size__|<^. "Share Size Information":#share_size| |>^. +29|<^. __Big_flag__|<^. "Big Flag":#big_flag| |>^. +2A-3F|<^. |<^. Reserved, must be 0| h4(#disc_description). Disc Description Flags |_<^{width:4em}. Bits|_<^. Meaning| |<^. 0 - 5|<^. Lowest numbered sector id on a track| |<^. 6|<^. Treat sides as a sequence (not interleaved), if set| |<^. 7|<^. Disc is 40 track, if set| h4(#share_size). Share Size Information |_<^{width:4em}. Bits|_<^. Meaning| |<^. 0 - 3|<^. Log2 share size granularity (in sectors)| |<^. 4 - 7|<^. Reserved, must be zero| h4(#big_flag). Big Flag |_<^{width:4em}. Bits|_<^. Meaning| |<^. 0|<^. Identified as 'Large' disc, if set| |<^. 1 - 7|<^. Reserved, must be zero| h4(#disc_densities). Disc Densities |_<^{width:4em}. #|_<^. Meaning| |<^. 0|<^. Hard disc| |<^. 1|<^. Single density (125 Kbps FM)| |<^. 2|<^. Double density (250 kbps FM)| |<^. 3|<^. Double density (300 kbps FM), i.e. higher rotation speed DD| |<^. 4|<^. Quad density (500 kbps FM)| |<^. 8|<^. Octal density (1000 kbps FM)| h4. Notes There are two different FileCore Disc descriptor formats. The earlier version only supports small hard discs, while the later version supports larger discs. fn1. Small disc are returned on versions prior to RISC OS 3.60 fn2. Large discs are returned on RISC OS 3.60 and later h4. See also * [[Disc Cycle ID]] * [[FileCore]] * [[File Types]]