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Overview of Unix Operating SystemLast revision August 2, 2004 Strictly speaking, the term Unix Operating System refers only to those operating systems that have passed the Unix standards test of the X-Open Foundation, which owns the Unix trademark. X-Open acquired the trademark and standards from AT&T, the original creator of Unix. In practice, Unix refers to any operating system that provides the programs, commands, and programming interfaces normally found on official Unix. There are two main variants of Unix, which have roots in the same original source code from the 1970s and 1980s: System V (AT&T) and Berkeley Unix, whose last version is called 4.4BSD. There is also one important Unix work-alike-- Linux -- that looks like Unix to most users and programmers, but has a totally separate origin and shares no source code with official Unix. Also, note that the core of the new MacOS X is straight Berkeley Unix. To the normal user, the biggest difference among these variants of Unix is the type of shell, or command interpreter, you normally use when connected from a command line login, or the look and feel of the graphical desktop when connected via an X Window session. The general user programs and utilities are pretty much standardized among Unix versions. For the system administrator or programmer who needs to use system routines, there are some important differences. The School of Earth Sciences main server computer, pangea, runs HP Tru64 Unix, a version originally developed by the former Digital Equipment Corporation, which was acquired by Compaq Computer Corporation, which was recently acquired by Hewlett-Packard Corporation. This version has internals based on System V Unix, but a user interface more similar to Berkeley Unix.
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