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Basic Unix

Operating System Background

By definition, an operating system (OS) is the set of programs which provide for the basic operation of a computer. For example, the computer's display is controlled by the OS. Without an OS, a computer would not know what to project on its screen. The system used on Eos workstations is called UNIX. However, UNIX is not a single OS, but a family of OS's that run on a wide variety of computers.

Ken Thompson, Dennis Ritchie, and Brian Kernighan were authors of the first version of the UNIX. It was completed in November, 1971, a good ten years before the IBM PC and MacIntosh. All three men worked for AT&T at Bell Labs. The first version widely available commercially was edition 6, released in May, 1975.

There are currently several versions of UNIX on various hardware platforms, i.e. PC's, Workstations, mainframes, etc. UNIX is a major competitor in the operating system marketplace and is threatening the MS-DOS and Windows world of the PC's. Our version, written by Digital Equipment Corp, is known as ULTRIX. Others on the Eos system include:

HP/UX
IBM AIX
SunOS

The version working at each lab location depends on the manufacturer of the computing equipment.

Operating System Concepts

When considering the actual functions of an OS, one discovers there is much more than actually meets the eye. In order for a computer to function correctly, all OS's must:

manage memory
control hard and floppy disk drives
load and execute programs
provide services to running programs
provide the user with a means inputting and outputting information

In practice, an OS can be divided into two key components:

Command Line Interface (CLI)

Kernel

On Eos, the command line is indicated by the prompt "bae%". In the case of UNIX, the CLI is provided by a program known as the shell. Two of the most popular shells are the Bourne shell, one of the oldest and the C shell. The % symbol on the end of our prompt indicates we are running the C shell. As part of its function, the shell CLI communicates information to and from the Kernel.