A peripheral device is defined as a computer device, such as a keyboard or printer these auxiliary devices are intended to be connected to the computer and used. Peripheral devices can be external or internal.

• Examples of external peripherals include mouse, keyboard, printer, monitor, external Zip drive or scanner.


• Examples of internal peripherals include CD-ROM drive, CD-R drive or internal modem.

Mainly Computer Peripherals are classified into two types: 1. Input devices: An input device is any hardware device that sends data to a computer, allowing you to interact with and control the computer.

• Keyboard
• Mouse
• Joy Stick
• Light pen
• Track Ball
• Scanner
• Microphone
• Bar Code Reader

Keyboard A keyboard is the most common and very popular input device which helps in inputting data to the computer. The layout of the keyboard is like that of the 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 the Internet.

• Typing keys: These keys include the letter keys (A-Z) and digit keys (0-9) which generally give the same layout as that of typewriters


• Numeric Keypad: It is used to enter 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.


• Function Keys: The 12 function keys are present on the keyboard which are arranged in a row at the top of the keyboard. Each function key has unique meaning and is used for some specific purpose


• 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).


• Special Purpose Keys: Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.

Mouse A mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm size box. It has two buttons called left and right button and a wheel are present between the buttons.
Advantages:

• Easy to use
• Not very expensive
• Moves the cursor faster than the arrow keys of a keyboard.

Joystick Joystick is also a pointing device which is used to move cursor position on a monitor screen. The function of a joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.
Joystick is also a pointing device which is used to move cursor position on a monitor screen. The function of a joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.
Light Pen Light pen is a pointing device which is similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor.
Track Ball Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. A track ball comes in various shapes like a ball, a button and a square.
Scanner Scanner is an input device which works more like a photocopy machine. It is used when some information is available on a paper and it is to be transferred to the hard disc of the computer for further manipulation.
Digitizer Digitizer is an input device which converts analog information into digital form. Digitizer can convert a signal from the television or camera into a series of numbers that could be stored in a computer.
Microphone Microphone is an input device to input sound that is then stored in digital form. The microphone is used for various applications like adding sound to a multimedia presentation or for mixing music.
Bar Code Readers Bar Code Reader is a device used for reading bar coded data (data in form of light and dark lines). Bar code data is generally used in labeling goods, numbering the books etc. Bar Code Reader scans a bar code image, converts it into an alphanumeric value which is then sent to the computer to which bar code reader is connected.
2. Output Devices Output devices are used to communicate the result with users. A user can read the result through output devices, which means the output devices are used to view the information. Monitor, speakers and printers are a few examples of output devices.
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

Cathode-Ray Tube (CRT) Monitor The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity, or resolution.
Flat-Panel Display Monitor The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT.
Printers Printer is an output device, which is used to print information on paper.
There are two types of printers:

• Impact Printers
• Non-Impact Printers

Impact Printers The impact printers print the characters by striking them on the ribbon which is then pressed on the paper. Characteristics of Impact Printers are the following:

• Very low consumable costs
• Very noisy
• Useful for bulk printing due to low cost
• There is physical contact with the paper to produce an image

Non-impact Printers Non-impact printers print the characters without using ribbon. These printers print a complete page at a time so they are also called as Page Printers.
These printers are two types

• Laser Printers
• Inkjet Printers

Laser Printers These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.
Inkjet Printers Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high-quality output with presentable features.
Speakers It is an output device that generates the sound from the computer. It requires a sound card to connect the CPU to produce sound. These are used for listening audio files and watching the video files.