<P> Unix - like systems run on a wide variety of computer architectures . They are used heavily for servers in business, as well as workstations in academic and engineering environments . Free UNIX variants, such as Linux and BSD, are popular in these areas . </P> <P> Four operating systems are certified by The Open Group (holder of the Unix trademark) as Unix . HP's HP - UX and IBM's AIX are both descendants of the original System V Unix and are designed to run only on their respective vendor's hardware . In contrast, Sun Microsystems's Solaris can run on multiple types of hardware, including x86 and Sparc servers, and PCs . Apple's macOS, a replacement for Apple's earlier (non-Unix) Mac OS, is a hybrid kernel - based BSD variant derived from NeXTSTEP, Mach, and FreeBSD . </P> <P> Unix interoperability was sought by establishing the POSIX standard . The POSIX standard can be applied to any operating system, although it was originally created for various Unix variants . </P> <P> A subgroup of the Unix family is the Berkeley Software Distribution family, which includes FreeBSD, NetBSD, and OpenBSD . These operating systems are most commonly found on webservers, although they can also function as a personal computer OS . The Internet owes much of its existence to BSD, as many of the protocols now commonly used by computers to connect, send and receive data over a network were widely implemented and refined in BSD . The World Wide Web was also first demonstrated on a number of computers running an OS based on BSD called NeXTSTEP . </P>

Windows 7 is a single user operating system