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[[Category:Cpctech.org]]
<div style="border: 1px solid rgb(228, 222, 222); margin: 0px 0px 5px; padding: 0.5em 1em; background-color: rgb(249, 249, 249);"><center>'''''This article originally came from Kevin Thackers' archive at [http://www.cpctech.org.uk http://www.cpctech.org.uk].'''''</center></div>
|-
| 1
| 0Drive Definition Byte
|-
| 1
|}
The drive definition byte is as follows: {| border="1"|-! Bit ! Description|-| 3 | Double-stepped if set|-| 2| Head when not double-sided|-| 1 | Unused|-| 0| Double-sided when set|} If the image is double-sided, alternate heads are stored for each cylinder. ARC files written by older versions of Xexor have the following header(ie. XA and DDB missing):
{| border="1"
|-
| 14
| Sector has Deleted Data Address Mark if set (DDAM)
|-
| 13
| Sector data is present if set (not empty)
|}
Sector data is also assumed to be present if bit 14 is set, regardless of bit 13.
== Compression scheme ==
