System V release of the AT&T Unix originally created by Dennis Richie and Ken Thompson. Sometimes referred to as SRV. After V, they stopped changing the system number and started versioning the V release. The last release from AT&T was System V Release 4, commonly known as SVR4. SCO claims to have continued on, with System V Release 7 being their latest release. Solaris is an example of a SysV-based Unix. Linux will seem like SysV to someone familiar to BSD, but like BSD to someone familiar to SysV. See also BSD and this excellent article by Dru Lavigne at ONLamp for more information on differences between SysV and BSD systems.