Page 61 - DCAP101_BASIC_COMPUTER_SKILLS

Basic Computer Skills

Notes to that menu item or icon. With a click of the mouse’s button, the system can then be
notified of this choice. Note that notifying the system of a particular choice, out of the
various options provided by the software, is much easier a mouse than pressing various
key combinations. With proper software, a mouse can also be used to draw picture on the
screen and edit text.
The roller-ball based mouse is now being replaced with optical sensor based mouse. The
optical sensor mouse has a light source with a sensor arranged in such a fashion that the
light coming from the source is detected by the sensor after reflection from the surface.
The on-board electronics on the mouse uses the reflection differences to calculate the
direction and speed of movement and notifies the computer system. The optical sensor
mouse is more sensitive, easier, and smoother to use. Another innovation in mouse is to
have user-programmable buttons on the sides and the middle button on top is replaced
with a wheel that can be rotated as scroll to scroll the screen display and can also be
pressed as a button.

4.2.1.4 Data Scanning Devices

Data scanning devices are input devices used for direct data entry into a computer system
from source documents. Some of them are also capable of recognizing marks or characters.
These devices have following characteristics:
1. They eliminate the need for manual entry of data by human beings. Automatic entry
of data with their use improves data accuracy and increases timeliness of the information
processed.

2. They demand high quality of input documents because of direct data entry from source
documents. Documents that are typed poorly, have strikeovers, or have erasures are
normally rejected.
3. Form design, and ink specification usually becomes more critical with the use of these
devices than when keyboard devices are used to key in data from forms. Data scanning
devices are of many types. Commonly used ones are described below.

Image Scanner
An image scanner is an input device that translates paper documents into an electronic
format that can be stored in computer. The input documents may be typed text, pictures,
graphics, or even handwritten material. This input device has been found to be very useful
in preserving paper documents in electronic form. A copy of a document stored in a
computer in this manner will never deteriorate in quality or become yellow with age, and
can be displayed or printed, whenever desired. The stored images can even be altered and
manipulated in interesting ways, if the computer has image-processing-software.

Image scanners come in various shapes and sizes. Two commonly used types are:
I. Flatbed scanner. A flatbed scanner is like a copier machine consisting of a box having
a glass plate on its top and a lid that covers the glass plate. A document to be scanned
is placed upside down on the glass plate. A light source, situated below the glass
plate, moves horizontally from one end to another when activated. After scanning
one line, the light beam moves up a little and scans the next line. The process is
repeated for all the lines. It takes about 20 seconds to scan a document of size 21 cm
x 28 cm.

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