---
name: "diskdefs"
section: "5"
platform: "linux"
package: "cpmtools"
version: "2.23-7"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/diskdefs"
---

# diskdefs(5)

CP/M disk and file system format definitions

## NAME

diskdefs - CP/M disk and file system format definitions

## DESCRIPTION

The diskdefs file contains CP/M format descriptions, because CP/M in general 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]
  [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.

## SEE ALSO

[*cpm*(5)](/cpm/5.md)