DOS XL is a Disk Operating System (DOS) written by Paul Laughton, Mark Rose, Bill Wilkinson and Mike Peters and produced by Optimized Systems Software (OSS) for Atari 8-bit microcomputers. It was designed to be compatible with Atari DOS which came shipped with Atari's disk-drives.
DOS XL from OSS is the sucessor of OS/A+ DOS. This command line DOS was delivered together with the Indus GT Drive and many OSS Language Products.