A multiuser, multitasking operating system that is widely used as the master control program in workstations and servers. The Open Group holds the trademark for the UNIX name (spelled in upper case) on behalf of the industry and provides compliance certification to the UNIX standard (see Single UNIX Specification).
Myriad commercial applications run on Unix servers, and most websites run under Linux, a Unix variant. Over the years, there have been many different Unix versions, and, except for the PC world, where Windows dominates, almost every hardware vendor offers Unix either as its primary or secondary operating system. Sun was singularly instrumental in commercializing Unix with its Solaris OS (formerly SunOS), and HP, IBM, SCO and Digital (before it was acquired by Compaq) were also Unix promoters.
From the Telephone Company
Both Unix and the C programming language were developed by AT&T, dating back to the early 1970s. Unix and C were freely distributed to government and academic institutions, causing it to be ported to a wider variety of machine families than any other operating system. As a result, Unix became synonymous with "open systems" and thrives today on virtually every hardware platform. See AT&T.
Command Lines and GUIs
The Unix OS is made up of the kernel, file system and a shell, which is the command line interface with more than 600 commands for manipulating data and text. The major user interface shells are the original Bourne shell, C shell and Korn shell. Many commands are cryptic, but just as Windows hid the DOS prompt from users, graphical interfaces provide a Windows-like look into Unix and Linux. Linux desktops offer various GUIs, and many pundits claim that Apple created the best GUI for Unix with its OS X operating system, which is also Unix based. See Unix history, Mac OS X and Linux.
Unix Is Everywhere
Unix components are world class standards. The Internet runs on Unix protocols such as TCP/IP for network transfer and SMTP for e-mail. NFS provides file sharing, Kerberos provides network security, and X Window lets users execute programs remotely in a mostly Unix environment. See POSIX, BSD Unix, USENIX and UDI.
Versions of Unix that are compliant with The Open Group's UNIX specifications include Sun's Solaris, HP's HP-UX, IBM's AIX and z/OS and SCO's UnixWare. See Open Group, Solaris, HP-UX, AIX, z/OS, Mac OS X and Linux.
In the following illustrations, notice how many workstations and servers have run and still run under Unix.
Almost All Unix
Except for Windows, all these operating systems are Unix based. This list described the various versions of the Prince PDF converter software from YesLogic Pty. Ltd. (www.princexml.com).