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Unformatted text preview: ster I/O devices.
An input device is an electromechanical device that accepts data from the outside world
and translates them into a form the computer can interpret. A wide range of input devices
is available today that can be broadly classified into the following categories:
1. Keyboard devices
2. Point-and-draw devices
3. Data scanning devices
5. Electronic cards based devices
6. Voice recognition devices 7. Vision based devices
8. Offline data entry devices
The various types of input devices along with their typical applications are described
Keyboard devices are the most commonly used input devices today. They allow data
entry into a computer system by pressing a set of keys (labeled buttons), which are neatly
mounted on a keyboard connected to the computer system. Keyboard devices can be
broadly classified into two types - general-purpose keyboards and special-purpose
keyboards. They are described below.
General-purpose keyboards are standard keyboards used with most computer systems.
They are called general-purpose because they have enough keys to make them useful for
any type of application. That is, they are designed to meet the data entry requirements of
a very wide range of computer users.
The most popular general-purpose keyboard used today is the 101-keys QWERTY
keyboard. It was introduced and promoted by IBM for use with IBM PCs and IBMcompatible PCs (personal computers). It is so called because it has altogether 101 keys
out of which the keys for alphanumeric characters follow the commonly used QWERTY
layout. The QWERTY layout has been adopted from the standard typewriter keyboard
layout. The positioning of the character keys in this layout ensures faster typing speed. In
this layout, the alphabetic keys are arranged so that the upper-left row of letters begins
with the six letters Q, W, E, R, T, and Y (see Figure 9.2). Designers of other keyboards
claim that their boards are easier to learn and use than the QWERTY keyb...
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This document was uploaded on 04/07/2014.
- Spring '14