This is a version of MS-DOS branded for the ITT XTRA personal computer.
This version added support for 10 MB hard disk drives and tree-structure filing system.
During its life, several competing products were released for the x86 platform, and MS-DOS itself would go through eight versions, until development ceased in 2000. Ultimately it was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI.