Introducing UNIX and Linux

The Computing Environment

Overview
What is a Computer?
Hardware
      Processors
      Input Devices
      Output Devices
Software
      Input and Characters
            Control Characters
      Application Programs
            Programming Languages
      The Operating System
      System Administration
History of UNIX and Linux
Conventions
Summary

The Operating System

The final piece of the jigsaw of modern computing, to make the hardware and software work together, and to make the different bits of hardware like the screen, keyboard and processor talk to each other, is what is known as the operating system, which is system software as opposed to application software. The operating system is a complex program (or collection of programs) that controls the internal operation of the computer to ensure that all of the different things that are taking place at the same time are done effectively and sensibly. For example, while the computer accepts input from the keyboard and displays output on the screen, it may also be processing some data and accessing the hard disk, all at the same time.

Just as there can be different processors, different screens and keyboards, and different application programs, so there can be different operating systems. If you've got this far, then we should be able to assume that you know that your particular operating system is (or is likely to become) UNIX or Linux, but you may also be familiar with Microsoft's Windows, with DOS (Disk Operating System), or with some other operating systems such as CPM (Control Program for Microcomputers) , MacOS, Multics, BeOS, PalmOS or VMS (Virtual Memory System).