2.1.5 Input Devices

Input devices allow users to enter data and information to the computer system. When
selecting input devices it is important to balance the speed and functions performed by
the input devices with their cost, control and complexity. Input devices vary from capture
specific types of data to more general purpose input devices. Following are some
examples.

Keyboard

The keyboard is also referred to as the primary input device of the computer system. The
keyboard has a similar layout to the typewriter, but has some additional keys that provide
additional functionality than a typewriter. In a computer, a keyboard converts letters,
numbers and other characters into electrical signals that are computer readable. These
special keys are Insert key, Enter key, Home key, Ctrl key, Alt key, etc. Keyboards come
in different shapes and sizes and may differ in the number of additional keys.

Pointing devices

Although keyboards are still the mostly widely used input devices to enter text into a
computer system, pointing devices are a better alternative for issuing commands and
responding to prompts displayed on the monitor. They work with the operating systems
Graphical User Interface (GUI) that presents you with icons, menus, windows, bars and
so on for your selection. Pointing devices use one of the most natural gestures of
humans i.e. the act of pointing. Mouse, trackballs, joysticks, touch screens are some of
the most frequently used pointing devices.

Mouse
The mouse is the second most common input device. A ball underneath rolls as
the mouse moves across the mouse pad.The cursor on the screen follows the
movement of the mouse. Buttons on the mouse can be clicked or double -clicked
to perform tasks, like to select an icon on the screen or to open the selected
document. There are new mouse models that do not have a ball. They use a
laser to sense the motion of the mouse instead.


Trackball


Trackball is a movable ball, on top of a stationary device, that is rotated with the
fingers or palm of the hand. Advantages of trackballs are that, it does not need as
much desk space as a mouse, and it is not as tiring since less motion is needed.
On the other hand it requires fine control of the ball with just one finger or thumb.

Joystick


A joystick is a pointing device that consists of a vertical handle like a gearshift
lever mounted on a base with one or two buttons. Joysticks are commonly used
in video games to control the cursor motion. A joystick gives a more natural
feeling of control for motion in games, especially those in which one is mimicking
flying a plane or spaceship.

Voice/Speech Recognition Systems

These devices can recognize human voices. These tools use microphones and special
software to record and convert the sound of the human voice into digital signals.
Speech recognition systems can be used on the factory floor to allow equipment
operators to give basic commands to machines while they are using their hands to
perform other operations. Voice-recognition is also used in security systems to allow only
authorized personnel into restricted areas. Since speech is the easiest, most natural
means of communication, speech recognition promises to be the easiest method for data
entry, word processing and conversational computing.

Digital Cameras

Digital cameras look very similar to regular cameras but record and store images or
video in digital form. After taking a picture, the images are electronically stored in the
camera.
Most often the image file is compressed and stored on the digital memory card to allow a
large number of photographs to be taken. The memory card is displayed like
another disk drive on your computer system when you connect the digital camera to the
computer system. Then images stored on the card can be downloaded to the computer
with the help of a cable which is connected from the camera to a port on the computer.
Alternatively, the images stored in the flash memory card of the diskette can be
downloaded by inserting it to the personal computer.

Terminals


Terminals are input devices that perform data entry and data input at the same time.
Data entry and input is through the keyboard and mouse. A terminal is connected to a
complete computer system by telephone lines or cables. They are inexpensive and easy
to use.
Point-of-Sale (POS) devices are terminals used in retail operations to enter sales
information into the computer system.

Magnetic Ink Character Recognition (MICR) Devices
Magnetic Ink Character Recognition (MICR) devices are used to read the data that is
placed at the bottom of a check or other form using a special magnetic ink. Humans as
well as computers can read this data. This technology is used by banks.

Light Pens

The light pen is a light-sensitive stylus, or a pen like device connected to the computer.
The user can bring the pen to the desired point on the screen. When the pen touches the
screen, it sends the information available at the location to the computer. Using the pen
input device it is possible to activate a command or cause the computer to perform a
task, enter handwritten notes and draw objects and figures.
These can be used to activate commands and place drawings on the screen.

Touch-Sensitive Screens

Touch screen is a video display screen that receives input from the touch of a finger or
stylus. These screens can act as input as well as output devices. Examples are
Automatic Teller Machines (ATMs) in banks and information kiosks.

Scanning Devices

Scanners generally convert text, drawings and photographs into digital form that can be
stored in a computer and then manipulated. Sometimes these scanners are called image
scanners or graphics scanners.

There are special purpose scanners such as fingerprint scanners which are used to scan
finger prints and barcode readers.

Barcodes are a set of dark lines that are used to uniquely identify an item or product.
Barcodes are found in many products ranging from books to canned fruits. This is a
convenient way of entering data without using a mouse or a keyboard by simply swiping
the printed barcode under the barcode reader.

These emit strips of LASER light and the reflected image is picked up by the light
sensors. The captured image is processed and the barcode is identified and passed on
to the computer system as an alphanumeric value. This value can be processed by the
program and a suitable response can be executed.

In retail operations barcode scanners are usually connected to POS devices. POS
devices are terminals used in retail operations to enter sales information into the
computer system.

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