Informatics practices 11th CBSE

1. INPUT, OUTPUT AND MEMORY DEVICES

2. An Input Device is any hardware component used to
enter data, programs, commands and user responses
into a computer.
There are a variety of input which are used by
computers. Some of them are general purpose, that
is, they may be used by any computer.
The input devices are as follows:

3. The Keyboard
Keyboard is a typewriter like a device which
is used to type in the letters, digits and
commands.
Working: Each key when pressed send a
digital code to the computer that determines
when key has been pressed.
Advantages: Most common and reliable of
inputting data. Available in variety of
formats.
Disadvantages: Not useful for entering
pictures, etc. Very slow for selecting various
objects on screen or moving object.
The Mouse
The mouse is a pointing device with a roller on
the base. Mouse controls movement of a
pointer.
Working: When a mouse moves on a flat
surface, the cursor on the screen also moves in
the direct of the mouse movement.
Types: Mechanical, Optical and Wireless
mouse.
Advantages: Ideal for pointing objects on
desktop. Most familiar and easy to use pointing
device.
Disadvantage: Need a flat space close to
computer. A mouse cant easily be used by a
note book.

4. Light Pen
A light pen is used as a pointing device. It
consists of a photocell mounted in a pen
shaped tube.
Working: When a pen is brought in front of a
picture elements of the screen, it senses light
coming from the limited field of view.
Advantages: Easy to use. Can directly draw on
screen.
Disadvantages: Not very accurate while
drawing. Expensive compared to other
pointing devices.
Touch screen
Touch screen is a type of display that has
touch-sensitive transparent panel covering the
screen.
Working: A grid of light beams criss-cross the
compiler screen. When you touch the screen,
the rays are blocked and computer senses and
identifies the object which u want.
Advantages: Easy to use. No training is
required.
Disadvantages: Not suitable for inputting bulk
data. Not very accurate while pointing small
areas.

5. Graphics Tablet
A Graphic Tablet enables you to enter
drawings and sketches into a computer.
Working: The tablet contains electronic
circuitry that enable it to detect movement
of the cursor and translates the movements
into digital signals that it sends to the
computer.
Advantages: Very useful in environment
involving move of drawings etc.
Disadvantages: Not very useful for pointing
and clicking object.
Joystick
The joystick is a device that lets the users
move an object on the screen.
Working: A joystick is a stick set in two
crossed grooves and can be moved left or
right, front or back. It is sensed by a
potentiometer.
Advantages: Useful to play computers on
computer. Gives immediate feel of
direction.
Disadvantage: Involves more arms and
wrist movement. Not very useful for
clicking objects.

6. Microphone
Microphone sends sound input to computers
through a special input devices.
Working: A mic converts the sound received
into computers format.
Advantages: Useful for inputting audio which
cant be input through other devices.
Disadvantages: Need specific and additional
hardware called Soundcard.
Optical Character Reader
An optical character reader is used to read character of
special type font printed on conventional paper with
ink.
Working: The characters are examined by passing
them under a strong light , which differentiates light
from inked areas.
Advantages: OCR is faster than typing a document
which is printed form.
Disadvantages: You need to buy scanner and OCR. Its
not completely accurate.

7. Scanner
A scanner is a device similar to a
photocopier. A scanner creates a electronic
form of image which can be manipulated.
Types: Hand-held, Flatbed, Drum Scanners.
Advantages: It is accurate and can produce
images with higher resolution.
Disadvantages: Image can take up a lot of
memory space. The output depends on the
quality of the document
Optical Mark Reader
Optical Mark Reader transcribes the marks
into electrical pulses which are transmitted to
the computer.
Uses: Objective types answer paper, various
type of surveys and order forms.
Advantages: A quick and reliable way of
inputting large volumes of simple data.
Disadvantages: Cant be used for bulk inputs.

8. Smart Card reader
The Smart Card Reader can
read information on smart
cards are called smart-card
readers. Smart card contains
a microprocessor that
retains certain security and
personal data in its memory
at all times
Bar Code Reader
A bar code reader emits a beam of
light which reflects off the bar code
image.
Advantages: Fast and reliable
method of inputting data. Can read
from curved or upside down surface.
Disadvantages: Input is limited to a
number code.

9. Biometric Sensors
Biometric is a technology that
verifies a persons identity by
measuring a unique-to-the
individual biological trait.
Web Camera
A webcam is a loosely used
term for any camera that
generates images that can
be accessed by and
displayed on web browsers
through servers

10. The Output Devices produce output of the
machine in human readable form. To allow this,
the computer must be connected to an output
device.
The output devices are as follows:

11. Monitors
Monitor is the most common form of output from a computer. The picture on a monitor is made up of
thousands of tiny coloured dots called pixels.
They are five types of monitor :
~CATHODE RAY TUBE (CRT):
The CRT works in the same way as a television – it contains an electron gun at the back of the glass tube.
When the electrons strike the phosphor dots they glow to give the colours.
~LIQUID CRYSTAL DISPLAY:
Liquid Crystal is the material used to create each pixel on the screen. TFT is a variant of LCD technology. LCDs
use much less power than a normal monitor.
~PLASMA MONITORS:
Plasma monitors or PDP (Plasma Display Panels) are flat panel displays. They offer a wide range of contrasts
and colours and have a long display life so they can be used for years without going dead.
~TOUCHSCREEN MONITORS:
Touchscreen monitors are built by combining touch sensitive materials with a durable but sensitive outer
material that protects the monitors from fingers but still allows the monitor to detect where a person is
placing his fingers.
~ORGANIC LIGHT EMITTING DISPLAY (OLED) MONITORS:
OLED monitors are created from pushing an electronic current through organic materials, causing these
materials to glow. The price of OLED monitors is much more than traditional CRT or LCD monitors .

13. Cathode Ray Tube (CRT) Liquid Crystal Display (LCD) Plasma Monitor
Touchscreen Monitor Organic Light Emitted Display

14. PRINTERS
A most convenient and useful method by which the
computer can deliver information is by means of
printed characters.
Printers can be divide into two distinct categories:
~Impact Printers
~Non-Impact printers

15. IMPACT PRINTERS
In these printers, there is mechanical contact between the print
head and paper. Most common impact printer is Dot Matrix
Printer. Dot Matrix Printer(DMP) is the most popular serial
printer i.e., it prints one character at a time.
 Low operating costs
 Can print on continuous
stationary.
 Using carbonated paper,
DMPs can create carbon
copies.
ADVANTAGES: DISADVANTAGES:

16. Non-Impact Printers
In these printers, there is no mechanical contact between the print head and paper.
Advantages of non-impact printer are: high speed, cost effective, better quality.
These printers can primarily be categorised as follows:
Electromagnetic printers: By using magnetic
recording techniques, a magnetic image of
what is to be printed can be written on drum
surface.
Thermal printers: An electric pulse can be
converted to heat on selected sections of a
printing head or on wires or nibs
Electrostatic printers: For electrostatic
printers the paper is coated with a non
conducting dielectric material which holds
charges when voltages are applied with
writing “nibs”(heads).

17. Inkjet printers: Some printers direct a high-velocity stream of ink toward the paper
ADVANTAGES: DISADVANTAGES:

18. Laser Printers: these printers make use of office copier technologies. The toner is then
permanently fused on paper with hot or pressure.
ADVANTAGES: DISADVATAGES:

19. Plotters are the output devices that produce good qualities drawings and graphs. There are two types of plotters :
drum plotter and flat bed plotter
PLOTTERS
ADVANTAGES: DISADVANTAGES

20. SPEAKERS
Speakers have become key sound-output systems. Speakers
receive the sound in form of electric current from the sound
card and then convert it to sound format. This way pressure
vibration are generated that create sounds.

21. The Main Memory is also know as the Immediate
Access Store (IAS). IAS holds the data and programs
needed at that instant by CPU. The CPU reads the data
and program kept on secondary storage into the main
memory, temporary i.e., as long as they are being
processed.
Units of memory:
The computer store and process data in the form of
binary numbers. A binary number is either 0 or a 1,
and is known as bit.

23. 1-Random Access Memory
The Random Access Memory is
a form of RAM chips. The data is
held in RAM but temporarily the
data disappears if the power is
switched off. RAM is a volatile
memory.
2-Read Only Memory
The ROM is also in the form
of chips. The data is not
erased when the power is
switched off i.e., it is
permanent. ROM is a non
volatile memory.

24. Cache Memory
Cache Memory are used in
modern, medium and high-
speed CPU’s to hold
temporarily those
positions of the content of
main memory which are
currently in use.
It is a fast and small
memory which stores the
copy of data which is
frequently used from main
memory.

25. Since primary memory has a limited storage capacity and is
not permanent, secondary storage devices are used to store
large amount of data permanently.
There are various types of secondary devices available
these days. Some most comma storage devices are:
~Hard Disk
~Floppy disk
~CD ROMs
~DVDs

26. Floppy Disks
The floppy disks are one of the oldest
type of portable storage device still in
use.
The floppy device enables one to
transfer small files between
computer and also to store data.
A floppy disk is made up of a
substance called Mylar.
Hard Disk
The hard disk memories store information one
or more circular platters which are continually
spinning.
Concentric circle on the magnetized surface of
the magnetic disk are known as Tracks. These
tracks are divided into invisible segments
called sectors.
Advantages: Large storage capacity. Permanent
storage.
Disadvantages: Far slower than RAM/ROM.
The disk cannot be transferred to another
computer.

27. Magnetic Tape
Magnetic Tape is a
sequential storage medium
used for data collection,
backup and archiving. It is
called a data storage
cassette.
Compact Disks (CDs)
1- CD-ROM : This is used to store
information and cannot be used
to store data.
2- CD-R : Data can be recorded on
this disk only once.
3- CD-RW : CD-RW is a erasable
disk you ca write on multiple
times.

28. DVDs
1- DVD-ROM : It is a highly capacity
optical disk.
2- DVD-R: It is similar to CD-R’s allow
users to write on the disc once but
read it many times.
3- DVD-RW : It is the most writable
form DVD. We can erase and read
many times from there.
Pen/Thumb- Flash Memories
Flash is a solid state memory
i.e., it has no moving parts
unlike magnetic storage devices.
The data is retained in Flash
even when the power is
switched of.

29. Blu-Ray disc
Blu-Ray is a successor to
DVD. Blu-Ray’s standard
storage capacity is enough
to store continues backup
copy of mort people’s hard
drives on a single disc.
Cloud Storage
Cloud storage is the
newest way of storing
files and data. The
cloud storage s a
mechanism not a
physical storage device.