Chapter No. 3 Input / Output Devices

Chapter No. 3 Input / Output Devices
Chapter No. 3
Input / Output Devices
Complete the following statements.
i) A standard arrangement of keys on a keyboard is the ___________________.
ii) A mouse is a pointing device used to select ________________________.
iii) A trackball is almost like a _______________ turned upside down.
iv) Translating voice to text is capability known as ______________________.
v) VDU is an ________________ device.
ii) various option
iii) mouse
iv) voice recognition
v) output
Tick (
) the following statements either true or false.
Input devices are used to enter only data into a computer.
Alphabet keyboard consists of keys from A to Z and 0 to 9.
A scanner picks every bit of the scanned text.
The disk drives are known as I/O devices.
A CD-writer in an I/O device.
i) False
ii) False iii) True
iv) True v) False
Encircle one choice A, B, C, or D in each of the multiple choice questions.
Which of the following is an output device?
a. Keyboard
b. Mouse
c. disk
d. scanner
Spacebar on a keyboard is a part of the:
a. Alphanumeric keypad
b. Numeric keypad
c. Function keys
d. Screen Navigation & editing keys
iii) Which of the following is not a pointing device:
a. Mouse
b. Joystick
c. Trackball
iv) Which of the following is used to produce soft copy:
a. Laser Printer
b. Plotter
c. CD-writer
v) The number of colours a CGA monitor display are:
a. 4
b. 16
c. 64
d. none
d. Dot-Matrix printer
d. 256
i) c
ii) a
iii) b
iv) c
v) a
Match the items given in Column I with those given in Column II
Column I
Column II
OCR software
Disk drives
Digital Camera
Scanner text
i) c
ii) d
iii) e
iv) b
v) a
Q.3.05 Name two very important input devices and describe their purpose in computer system.
Ans: Two important input devices are keyboard and mouse.
Keyboard is an important input device used to enter data and instructions into a computer. A
standard arrangement of keys is the QWERTY arrangement. Such keyboards have numeric
keypad at the right of the standard keyboard. A keyboard is connected with the system unit
through a dedicated keyboard port that contains signals as well as power lines. As soon as a key
is depressed for a character a signal for that character is generated that passes directly to the
main storage of the computer.
A mouse is a useful input device. It is a pointing device used to select various options. A mouse
is a small hand held unit with two or three buttons. It can roll over a small ball at its bottom.
When moved over a surface or pad, it moves a small object across the screen. A mouse is also
used to draw pictures on the screen and edit text.
Q.3.06 Name different areas of a keyboard and some key functions.
A keyboard may be divided into four general areas:
i) Alphanumeric keypad
ii) Numeric keypad
iii) Function keys
iv) Screen Navigation & Editing Keys
Following are some key functions of keyboard:
Function of the key
Escape key performs a variety of functions defined by the operating system.
It performs a command or function when used in conjunction with another key.
It moves cursor from final character position on line to the first position on the
next line.
The characters at the cursor position is deleted.
Page Up
Page up is a programmed controlled key, used to move the cursor to the
previous page.
Q.3.07 What is a mouse? How it works?
Ans: Mouse:
A mouse is a useful input device. It is a pointing device used to select various options. A mouse
is a small hand held unit with two or three buttons.
Working of Mouse:
It can roll over a small ball at its bottom. When moved over a surface or pad, it moves a small
object across the screen. A mouse is also used to draw pictures on the screen and edit text.
Q.3.08 Describe the working and uses of a trackball.
Ans: Working of Trackball:
A trackball is pointing device almost like a mouse turned upside down. The user controls the
cursor on the screen by rolling a plastic ball with a fingertip or wrist. To execute commands
with a trackball, one or more buttons are pressed, much in the same way as is done with a
mouse. The cursor can be moved around on the screen by rolling the ball with a thumb or
Uses of a trackball:
Trackball is popular among users of laptop computers. It can be used for handicapped people
who may have difficulty pressing keys on a standard keyboard.
Q.3.09 What do you know about scanner? How scanner text can be edited?
Ans: Scanner:
Image scanner is a useful input device. It converts every bit of the scanned material into
electrical pulses. Suitable scanning software converts the printed documents, pictures or
photographs into digital files. The digital files so formed can be stored in computer’s memory.
How scanner text can be edited:
Optical character recognition (OCR) software translates the scanned document into text that
can be edited. To edit photographs, graphic software is used. You can insert a picture into a
text. For this, scan the required picture, copy it, and then paste it in your document.
Q.3.10 What is meant by voice recognition? Explain
Ans: Translating voice text is a capability known as voice recognition (or speech recognition).
With it you can speak to the computer rather than entering the data and command by typing.
You can control the computer with simple vocal commands such as shutdown or print.
A speech recognition system contains software. Once you have installed the software, you
would need to train the system to recognize your unique speech pattern. To train the system,
we simply talk into a microphone attached with it for at least 20 minutes. The system learns our
speech patterns and updates the vocabulary accordingly.
Q.3.11 What is a colour monitor? Describe some features of different coloured monitors.
Ans: Colour Monitor:
Colour monitors can display image in multiple colours. They can show all the colours of the
rainbow. Now-a-days LCD flats panel coloured monitors are becoming popular. LCD coloured monitors
are particularly suitable with laptop PC because they are lightweight, portable and use little power.
Colour monitors are classified by their image producing technology like
CGA (Colour Graphic Adapter)
It displays four colours at a resolution of 320 by 200 pixels.
EGA (Extended Graphic Adapter)
It produces image up to 16 different colours at a high resolution of 640 by 480 pixels.
VGA (Video Graphic Adapter)
VGA presents simultaneously up to 256 colors shades at resolutions are up to 720 by
400 pixels.
S-VGA (Super Video Graphic Adapter)
S-VGA monitors presents 60,000 to 16 million colours and from 800 by 600 to 1280 by
1024 pixels.
Q.3.12 Explain the difference between Impact and Non-Impact printers.
Impact Printers
These printers print by striking
ribbon against the paper.
These are slow printers due to
the slow mechanical movement
of the print head.
These are noisy printers.
These are low quality printers
Non-Impact Printers
These printers produce a image
without striking the paper.
These are much faster than impact
These printers produce much less
These are high quality printers.
Q.3.13 Explain the working of a dot-matrix printer.
Ans: Working of a dot matrix printer:
It uses tiny pins arranged to hit the ribbon and the paper. In dot matrix printer, each letter is
formed with the combination of dots. A dot matrix may have 9, 18, 24 or 32 pins arranged
vertically in a print head. The dot matrix printers arrange pins to print dots that form characters
and all kinds of images.
Q.3.14 Explain how ink-jet printer differs from Laser printer?
Ink jet printers work in the same way as dot matrix printers except that ink jet printers have
fine nozzles instead of tiny pins used in dot matrix print head. In ink jet printer nozzles spray a
stream of ink onto the paper. Because the ink is put directly on the paper, therefore, these
printers require ink in reservoirs instead of ribbon. Since no mechanical movement is involved,
hence these printers are much quieter and have speed of about 200 characters per second.
Q.3.15 What is a plotter? How it works?
Plotter are special output device that print out black/white or coloured graphics output.
Plotters produce large drawings or images such as construction plans of building or blue prints
of complex machines like aircraft design.
Working of Plotter:
In drum plotter the paper is placed over a drum that rotates back and forth to produce vertical
motion. The pen is mounted on a carriage that moves across the width of paper. The vertical
movement of paper and horizontal movement of pen create the require design.
In flatbed plotter paper is spread and fixed over a rectangular flatbed. Different types of pens
are used in it to draw various types of drawing and charts. The plotting pen is held above the
paper and can be moved up or down.
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