X-DDOS is a floppy disc and hard disc operating system from the german company Dobbertin Industrie Electronic. It provides 0.7 MB floppy disc formats for B drives and allows to access the [[Dobbertin Harddisc]] HD20. X-DDOS is delivered as a 16 KB EPROM with a lot of software and a manual.
X-DDOS has the ROM name 'XDDOS ROM' but shows a sign-on message of "X-DDOS 2.10 (C)1990 Dobbertin GmbH" * X-DDOS can be used as a rom 7 replacement.
== RSX commands ==
* XD-DOS 2.0 and 2.10 support the [[Dobbertin Harddisc|HD-20]] hard disc drive.
* XD-DOS auto detects if the HD20 is connected. A message "* Harddisc not active *" is displayed if it is not. This is shown below the ROM sign on message.
* XD-DOS maps the HD20 to four partitions with 5120 KB each. Each partition is accessed by using the logical drive letters D, E, F and G.