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

Input Devices

Although the processor is most critical, it is of little use if you can't display the results of the computation it performs, nor if you can't specify and modify the kinds of computation you want it to perform. For this reason, we need input and output devices - hardware components that allow users to interact with the processor in easy and convenient ways.

In order to instruct a computer to perform a task, we require a way to provide instructions as input. Perhaps the most recognisable input device is the keyboard (typically of the 'QWERTY' variety because of the layout of the keys, similar to a typewriter), which nearly all computers use to receive textual and numeric input. The keyboard is the most usual way in which people write programs or enter data on which those programs might operate. However, there are also many other ways to provide input to a computer. For example, many people now have scanners to enable graphical images to be provided as input. Similarly, digital cameras, bar-code readers in shops, and even sound recorders offer different ways of getting data to the processor. In this book, we will focus on the standard keyboard as our main input device, but we also note that the mouse, with the purpose of enabling the selection and movement of items displayed on the screen, is a vital part of modern computer systems.