Other

Mainframe operating systems, such as IBM's z/OS, and embedded operating systems suchas VxWorks, eCos, and Palm OS, are usually unrelated to Unix and Windows, except for WindowsCE, Windows NT Embedded 4.0 and Windows XP Embedded which are descendants of Windows,and several *BSDs, and Linux distributions tailored for embedded systems. OpenVMS fromHewlett-Packard (formerly DEC), is still under active development.Older operating systems which are still used in niche markets include the Windows-likeOS/2 from IBM; Mac OS, the non-Unix precursor to Apple's Mac OS X; BeOS; RISC OS; andAmigaOS.

Research and development of new operating systems continues. GNU HURD is designed tobe backwards compatible with Unix, but with enhanced functionality and a microkernelarchitecture. Microsoft Singularity is a research project to develop an operating system with bettermemory protection.