Introduction

UNIX is one of the world's most popular operating system. It is a trademark of The Open Group, but was originally developed by AT&T. UNIX is a real operating system. A real operating system has two minimum qualifications : more than one person can access the computer at the same time and while doing so, each person can run multiple applications. This is called being a multiuser and multitasking operating system. In UNIX, each user logs in using a login name set by the administrator. Optionally, the user must also supply a password. The password ensures the person logging on with the user login name is really who he or she claims to be. UNIX will run on nearly every platform made. Many vendors such as IBM, Hewlett-Packard and Sun purchased the source and have developed their own versions. When UNIX was first developed, the source was given out free to colleges and universities. At one point, the UNIX development went hayewire because people around the world began developing tools for UNIX. There was no guidance to all these development. Thus causing a lot of differentiation between different versions of UNIX. Finally, UNIX standards appears. Many of the standards fall under the IEEE POSIX.1 standard.