Peripheral devices are hardware components that can be connected to a computer to allow input or output of data. Some common input devices described include keyboards, mice, scanners, digital cameras, and touch screens. Output devices receive processed data from the computer and display it, such as monitors which form images from pixels.

2. Peripheral devices
• Peripheral devices are those devices that are linked
either internally or externally to a computer.
• These devices are commonly used to transfer data.
• Several devices can be used to receive data and display
processed data. The devices used to perform these
functions are called peripherals or I/O devices.
• Peripherals read information from or write in the
memory unit on receiving a command from the CPU.

3. Input device
• Input device enables the user to send data, information, or control signals
to a computer. The Central Processing Unit (CPU) of a computer receives
the input and processes it to produce the output.

4. Keyboard
• Keyboard is the most common and very popular input device
which helps to input data to the computer. The layout of the
keyboard is like that of traditional typewriter, although there are
some additional keys provided for performing additional
functions.
• Keyboards are of two sizes 84 keys or 101/102 keys, but now
keyboards with 104 keys or 108 keys are also available for
Windows and Internet.

5. keys on the keyboard
• The keys on the keyboard are as follows −
1. Typing Keys: These keys include the letter keys (A-Z) and digit keys (09) which generally
give the same layout as that of typewriters.
2. Numeric Keypad : It is used to enter the numeric data or cursor movement.
Generally, it consists of a set of 17 keys that are laid out in the same
configuration used by most adding machines and calculators.
3. Function Keys: The twelve function keys are present on the keyboard which are
arranged in a row at the top of the keyboard. Each function key has a unique meaning
and is used for some specific purpose.
4. Control keys: These keys provide cursor and screen control. It includes four directional
arrow keys. Control keys also include Home, End, Insert, Delete, Page Up, Page Down,
Control(Ctrl), Alternate(Alt), Escape(Esc).
5. Special Purpose Keys: Keyboard also contains some special purpose keys such as Enter,
Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.

6. Mouse
• Mouse is the most popular pointing device. It is a very famous cursor-
control device having a small palm size box with a round ball at its base,
which senses the movement of the mouse and sends corresponding
signals to the CPU when the mouse buttons are pressed.
• Generally, it has two buttons called the left and the right button and a
wheel is present between the buttons. A mouse can be used to control the
position of the cursor on the screen, but it cannot be used to enter text
into the computer.

7. Joystick
• Joystick is also a pointing device, which
is used to move the cursor position on a
monitor screen. It is a stick having a
spherical ball at its both lower and
upper ends. The lower spherical ball
moves in a socket. The joystick can be
moved in all four directions.
• The function of the joystick is similar to
that of a mouse. It is mainly used in
Computer Aided Designing (CAD) and
playing computer games.

8. Light Pen
• Light pen is a pointing device similar to a pen. It is used to select a
displayed menu item or draw pictures on the monitor screen. It consists of
a photocell and an optical system placed in a small tube.
• When the tip of a light pen is moved over the monitor screen and the pen
button is pressed, its photocell sensing element detects the screen
location and sends the corresponding signal to the CPU.

9. Track Ball
• Track ball is an input device that is mostly used in notebook or laptop
computer, instead of a mouse. This is a ball which is half inserted and by
moving fingers on the ball, the pointer can be moved.
• Since the whole device is not moved, a track ball requires less space than
a mouse. A track ball comes in various shapes like a ball, a button, or a
square.

10. Scanner
• Scanner is an input device, which works
more like a photocopy machine. It is used
when some information is available on
paper and it is to be transferred to the
hard disk of the computer for further
manipulation.
• Scanner captures images from the source
which are then converted into a digital
form that can be stored on the disk. These
images can be edited before they are
printed.

11. digitizer or graphics tablet
• A digitizer tablet (also known as a digitizer or graphics tablet) is a tool used
to convert hand-drawn images into a format suitable for computer
processing. Images are usually drawn onto a flat surface with a stylus and
then appear on a computer monitor or screen. Digitizer tablets can also be
used as an input device, receiving information represented in drawings
and sending output to a CAD (computer aided design) application and PC-
based software like AutoCAD.
• Digitizers are often used along with takeoff software because they can
quickly measure, transfer and store quantities seen on a blueprint.
Additional benefits are found in features such as a dimension list, which
can be saved and used for a future estimate.

12. Digital Camera
• A digital camera is an input device that captures
images (and sometimes video) digitally. Digital
cameras use an image sensor chip to capture
the image, rather than the film used by a
traditional camera.
• A camera that is always connected to your
computer with no storage could also be referred
to as a digital camera. However, it is more
appropriate to refer to this device as a webcam.
• A digital camera may be considered both
an input and output device (I/O device) as it can
both take pictures (input) and send them to your
computer (output).

13. webcam
• A webcam captures digital pictures as it is an input device. These
images are forwarded to the computer that moves them to a
server. Then, these pictures can be transmitted to the hosting
page from the server. Nowadays, most of the webcam is
connected to the USB
• or FireWire port on the computer or embedded into the display
with laptop computers. It includes characteristics such as:
• Especially from a video telephony perspective, the cost of
webcams is considered lower as compared to other models of
camera.
• The maximum resolution of a webcam is low as compared to
most handheld cameras.
• The webcam features are mainly dependent on the computer
processor as well as an operating system of the computer. They
can provide advanced features such as image archiving, motion
sensing, custom coding, or even automation. Furthermore,
webcams are used for social video recording, video
broadcasting, and computer vision and mainly used for security
surveillance and in videoconferencing.

14. OMR, OCR, MICR & Barcode reader
• 1. OMR stands for Optical Mark Reader this mean the device recognizes what you
have put/marked. An example of this is to read data from a lottery card.
2. OCR stands for Optical Character Recognition this means converting images of
text into an edible document. An example of this would be scanning a page of a
text book.
3. MICR stands for Magnetic Ink Character Reader this means a device that reads
the magnetic ink. An example of this is to input data from a bank cheque.
4. Barcode reader Barcode is a set of small bars of varying thickness and spacing
printed on the packages of products, on the back coverpages of books, tags etc.
The barcode reader uses an optical scanner to read product code and converts it
into electrical pulses. The device is connected to a computer and the information
read is passed to the computer in digital form for automatic bill generation and
updating of files. Thus, it is a direct data entry device and there is no need for an
operator to key in sales transaction data.

15. voice recognition
• voice input device A device in which speech is used to input data or
system commands directly into a system. Such equipment involves the use
of speech recognition processes, and can replace or supplement other
input device.
• Voice recognition systems listen to what people are saying and carry out
the instructions given to them when people speak. A microphone is used
to provide input for a voice recognition system. Currently these systems
are not very sophisticated and are used only for certain applications.
Existing voice recognition systems come in two different types :
• Systems which recognise only a few words but can understand most
peoples voices. e.g. telephone banking computers.
• Systems which recognise a wide vocabulary but need to be trained to
understand each different voice. e.g. automatic dictation systems.

16. Touch screen
• A touch screen is a display device that allows the user to interact with a computer
using their finger or stylus.
• They're a useful alternative to a mouse or keyboard for navigating a GUI (graphical
user interface).
• Touch screens are used on a variety of devices, such as a computer and laptop
displays, smartphones, tablets, cash registers, and information kiosks. Some touch
screens use a grid of infrared beams to sense the presence of a finger instead of
utilizing touch-sensitive input.
• Any computer device (including a touch screen) that takes input from the person
operating the device is considered an input device. The way you use your finger on
a touch screen is very similar to how you use a computer mouse on a desktop
computer

17. Output Device
• An output device is a piece of computer hardware that receives data from
a computer and then translates that data into another form. That form
may be audio, visual, textual, or hard copy such as a printed document.
• The key distinction between an input device and an output device is that
an input device sends data to the computer, whereas an output
device receives data from the computer.

18. Monitors
• Monitors, commonly called as Visual Display Unit (VDU), are the main
output device of a computer. It forms images from tiny dots, called pixels
that are arranged in a rectangular form. The sharpness of the image
depends upon the number of pixels.
• There are two kinds of viewing screen used for monitors.
– Cathode-Ray Tube (CRT)
– Flat-Panel Display

19. Cathode Ray Tube (CRT)
• CRT or Cathode Ray Tube Monitor is the typical monitor that you see on a desktop
computer. It looks a lot like a television screen, and works the same way. This type
uses a large vacuum tube, called cathode ray tube (CRT).

20. Thin-film transistor (TFT)
• A display screen made with TFT (thin-film transistor) technology is a liquid
crystal display (LCD), common in notebook and laptop computers, that has
a transistor for each pixel (that is, for each of the tiny elements that
control the illumination of your display). Having a transistor at each pixel
means that the current that triggers pixel illumination can be smaller and
therefore can be switched on and off more quickly.
• A TFT or active matrix display is more responsive to change. For example,
when you move your mouse across the screen, a TFT display is fast enough
to reflect the movement of the mouse cursor.

21. Liquid Crystal Displays (LCD)
• This type of monitors are also known as flat panel monitor.
Most of these employ liquid crystal displays (LCDs) to render
images. These days LCD monitor are very popular.

22. LED
• The LED monitor is an improved version of an LCD monitor. It also has a
flat panel display and uses liquid crystal display technology like the LCD
monitors.
• The difference between them lies in the source of light to backlight the
display. The LED monitor has many LED panels, and each panel has several
LEDs to backlight the display, whereas the LCD monitors use cold cathode
fluorescent light to backlight the display.Modern electronic devices such
as mobile phones, LED TVs, laptop and computer screens, etc., use a LED
display as it not only produces more brilliance and greater light intensity
but also consumes less power.

23. Projector
• A projector is an output device that takes images generated by a
computer or Blu-ray player and reproduce them by projection onto a
screen, wall, or another surface. In most cases, the surface projected onto
is large, flat, and lightly colored.
• For example, you could use a projector to show a presentation on a large
screen so that everyone in the room can see it. Projectors can produce
either still (slides) or moving images (videos). A projector is often about
the size of a toaster and weighs only a few pounds.

24. Printer
• Printer is another output device found in homes or workplace.
With printer you can send pictures, text and information directly from your
computer into printed version. The computer conveys the processed data to
the printer, which then physically print the pictures and content on the
paper.
• There are two types of printers −
– Impact Printers: Impact printers print the characters by striking them on
the ribbon, which is then pressed on the paper.
These printers are of two types −
• Character printers: Dot Matrix Printer(DMP), Daisy Wheel
• Line printers: Drum Printer, Chain Printer
– Non-Impact Printers: Non-impact printers print the characters without
using the ribbon. These printers print a complete page at a time, thus
they are also called as Page Printers.
These printers are of two types −
• Laser Printers
• Inkjet Printers

26. Plotter
• A plotter is a computer hardware
device much like a printer that is used
for printing graphics.
• Plotters can work on very large sheets
of paper while maintaining high
resolution.
• Plotters allow the same pattern to be
drawn thousands of times without any
image degradation.
• Plotters are quite large compared to a
traditional printer.
• Plotters are also much more expensive
than a traditional printer.

27. Speakers
• Speakers are most popular and portable
output device used with computers to
generate sounds.
• They receive signals from the
computer’s sound card and produce
audio in the form of analog sound
waves that are audible to the human
hear.
• Laptops and monitors often have built-
in speakers.
• Sound cards are necessary in the
computers for speakers to function.

28. VGA (video graphics array)
• Abbreviation of video graphics array, a graphics display system for PCs
developed by IBM.
• VGA systems provide a resolution of 720 by 400 pixels. In graphics mode,
the resolution is either 640 by 480 (with 16 colors) or 320 by 200 (with 256
colors). The total palette of colors is 262,144.
• Unlike earlier graphics standards for PCs -- MDA, CGA, and EGA -- VGA uses
analog signals rather than digital signals. Consequently, a monitor designed
for one of the older standards will not be able to use VGA.
• All PCs made today support VGA, and possibly some other more advanced
standard.

29. SVGA (Super VGA)
• Short for Super VGA, a set of graphics standards designed to offer greater
resolution than VGA. SVGA supports 800 x 600 resolution, or 480,000 pixels.
• The SVGA standard supports a palette of 16 million colors, but the number of
colors that can be displayed simultaneously is limited by the amount of video
memory installed in a system. One SVGA system might display only 256
simultaneous colors while another displays the entire palette of 16 million colors.
• The SVGA standards are developed by a consortium of monitor and graphics
manufacturers called VESA.

30. XGA(extended graphics array)
• XGA are generally more expensive, and are an equally popular resolution
format to SVGA.
• Short for extended graphics array, a high-resolution graphics standard
introduced by IBM in 1990.
• XGA was designed to replace the older 8514/A video standard.
• It provides the same resolutions (640 by 480 or 1024 by 768 pixels), but
supports more simultaneous colors (65 thousand compared to 8514/A's
256 colors).

31. Hard Disk
• A hard disk is a computer's permanent
storage device.
• It is a non-volatile disk that permanently
stores data, programs, and files, and
cannot lose store data when the
computer's power source is switched off.
• it is located internally on computer's
motherboard that stores and retrieves
data using one or more rigid fast rotating
disk platters inside an air-sealed casing.
• It is a large storage device, found on every
computer or laptop for permanently
storing installed software, music, text
documentation, videos, operating system,
and data until the user did not delete.

32. Floppy Disk
• A floppy disk is a secondary storage system
that consisting of thin, flexible magnetic
coating disks for holding electronic data such
as computer files. It is also known as Floppy
Diskette that comes in three sizes like 8
inches, 5.5 inches and 3.5 inches. The stored
data of a floppy disk can be accessed through
the floppy disk drive. Furthermore, it is the
only way through a new program installed on
a computer or backup of the information.
However, it is the oldest type of portable
storage device, which can store data up to
1.44 MB. Since most programs were larger,
that required multiple floppy diskettes to
store large amounts of data. Therefore, it is
not used due to very low memory storage.

33. CD (Compact Disc)
• A CD is an optical disk storage device, stands for Compact
Disc. It is a storage device used to store various data
types like audio, videos, files, OS, Back-Up file, and any
other information useful to a computer. The CD has a
width of 1.2 mm and 12 cm in height, which can store
approximately 783 MB of data size. It uses laser light to
read and write data from the CDs.
• Types of CDs
• CD-ROM (Compact Disc Read Only Memory): It is mainly
used for bulk size mass like audio CDs, software and
computer games at the time of manufacture. Users can
only read data, text, music, videos from the disc, but they
cannot modify or burnt it.
• CD-R (Compact Disc Recordable): The type of Compact
Disc used to write once by the user; after that, it cannot
be modified or erased.
• CD-RW (Compact Disc Rewritable): It is a rewritable CD
disc, often used to write or delete the stored data.

34. VCD (video CD or video compact disc)
• VCD (also called video CD, video compact disc or "disc") is a compact
disk format based on CD-ROM XA that is specifically designed to hold
MPEG-1 video data and to include interactive capabilities. VCD has a
resolution similar to that of VHS, which is far short of the resolution of
DVD. Each VCD disk holds 72-74 minutes of video and has a data transfer
rate of 1.44 Mbps. VCDs can be played on a VCD player connected to a
television set (in the same way that video cassettes can on a VCR) or
computer, on a CD-i player, on some CD-ROM drives, and some DVD
players.

35. DVD Drive/Disc
• DVD is an optical disc storage device, stands
for Digital Video Display or Digital Versatile
Disc.
• It has the same size as a CD but can store a
larger amount of data than a compact disc. It
was developed in 1995 by Sony, Panasonic,
Toshiba and Philips four electronics
companies.
• DVD drives are divided into three types, such
as DVD ROM (Read Only Memory), DVD
R (Recordable) and DVD RW (Rewritable or
Erasable).
• It can store multiple data formats like audio,
videos, images, software, operating system,
etc.
• The storing capacity of data in DVD is 4.7 GB
to 17 GB.

36. Cache Memory
• It is a small-sized chip-based computer
memory that lies between the CPU and
the main memory.
• It is a faster, high performance and
temporary memory to enhance the
performance of the CPU.
• It stores all the data and instructions that
are often used by computer CPUs.
• It also reduces the access time of data
from the main memory.
• It is faster than the main memory, and
sometimes, it is also called CPU memory
because it is very close to the CPU chip.
• It is very costly as compared to the Main
memory and the Secondary memory.