1. The other major versions of the Unix operating system apart from BSD. Developed by AT&T. Later versions of Unix such as SunOS combined the best features of System V and BSD Unix.

2. A supplier of Unix open systems for Intel x86 processors. They supply products from SCO and Solaris and offer general support for Unix, TCP/IP, and Internet. They serve and create third-party WWW pages and provide on-line support for commercial and non-commercial applications.

See also System V Interface Definition.