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Peripherals Device

Auxiliary equipment used in computer like input device, output device, storage device, communication device or other functions under the direct control of a computer.
  • Input device - A computer hardware or device capable of accepting data or instructions. E.g keyboard, mouse, light pen, joy stick, bar code reader, scanner, microphone etc
  • Output device - A Computer hardware of device capable of displaying the result of the processed data. E.g monitor (VDU), printer, plotter, speaker etc.
  • Storage device - A computer hardware devices used for storing information permanently. It is also known as secondary memory. E.g hard disk, floppy disk, compact disk, pen drive etc
  • Communication device - microphone, modem, router

Input Device

  • Keyboard:- Keyboard is a most common data entry device. Using Keyboard, User can type text and execute commands.
    • It is known as standard input device.
    • Use keyboard in GUI and CUI.
    • No of Keys on Keyboard
      • minimum number of keys → 101 keys (without WIN key)
      • minimum number of keys → 104 keys (with WIN key)
      • minimum number of keys → 84 keys (on Laptop)
    • Layout of keyboard:- There are three type of layout of keyboard
      • QWERTY
      • AZERTY
      • DVORAK

Note: QWERTY is the most common and standard Layout of the keyboard.

Another Keys on Keyboard

  • Function Key:- There are 12 function keys available on the keyboard. F1 to F12.
  • Modifier key:- Ctrl key, Alt key and Shift key are the modifier key.
  • Toggle Key:- Num Lock, Caps Lock and Scrl Lock are known as toggle key.
  • Mouse:- It is known as standard pointing device. You can use mouse only in GUI. Mouse was invented by Douglas Engelbart in 1967. There are two type of mouse. These are
    • Mechanical mouse
    • Optical Mouse
  • Trackball:- Trackball is another pointing device that is used instead of mouse. Now a days trackball is used to control cursor movement on mobile phone to access internet.
  • Light pen:- It is also a pointing device. You can use light pen for digital signature. A light pen can work with any CRT- based monitor, but not with LCD screens, projectors or other display devices.
  • Joy Stick:- It is also known as pointing device. Joystick are used for computer games as they provide a better control.
  • Scanner:- A scanner allows you to capture documents or pictures that are printed on paper and turn them into digital format to be viewed on a computer. Scanners can be of different Types:-
    • Handheld scanner:- To use handheld scanner, you simply pass the scanner over the image or document you want to scan.
    • Flatbed scanner:- The flatbed scanner is similar to a photocopier machine. You can place an image or document on the glass scanning surface to scan.
  • Microphone:- A microphone is a device to input sound information. It allows you to record sound and voice to place onto the computer.
  • Barcode Reader:- Barcodes are different groups of vertical bars that can be read by a barcode reader. Barcodes are printed on nearly every products that you can buy. A Barcode reader is also known as Point of sale scanner.
    Barcode:- A bar code is the small image of lines (bars) and spaces that is affixed to retail store items, identification cards, and postal mail to identify a particular product number, person, or location. In Barcode, there are 13 digit available which is divided into 4 section.
    • First 2 digit—(1-2) → Country code
    • Next 5 digit----(3-7) → Manufacturing code
    • Next 5 digit—(8-12) → product code
    • Last digit—(13) → Check code
  • Optical Character Reader (OCR):- OCR is the recognition of printed or written text characters by a computer. This involves photo scanning of the text character-by-character, analysis of the scanned-in image, and then translation of the character image into character codes. OCR is being used by libraries to digitize and preserve their holdings.
  • Optical Mark Reader (OMR):- OMR is a device which can detect the presence or absence of a mark on a paper. Light is incident onto the paper and the reflected light is detected. OMR is used in reading answer sheet. Questionnaires.
  • Magnetic Ink Character Recognition (MICR):- MICR use special ink which can be magnetized, to print characters that can then be read and decoded by special magnetic devices. This system is widely used by banks for processing cheques. The check number, the bank and branch code and the account number are printed with ink containing magnet particle of iron oxide.

Output Device

Monitor:- Monitor is known as Standard output device. It is also known as visual display unit. The monitor displays the computer's user interface and open programs, allowing the user to interact with the computer.

Monitors colour Offered by Various video standards

  • Monochrome → Mono means single and chrome means colour i.e. black and white.
  • Colour
    • CGA (Colour Graphics Adapter): 4color/resolution 320*320
    • EGA (Enhanced Graphics Adapter): 16 colour/resolution 640*350
    • VGA (Video Graphics Array): 256 colour/resolution 640*480
    • XGA (Extended Graphics Array): 65536 colour/resolution 800*600 - true colour and 1024*768
    • SVGA (Super Video Graphics Array): 16,777,216 colour/resolution 1280*1024
  • Printer:- Printer is output device that prints text or image on paper. The output given out by the printer on a paper is called hard copy. Printers are divided into two parts:
    • Impact Printer:- Impact printers are the oldest printer still in action. With this type of printer something strikes paper and ribbon together to form a character. e.g dot matrix printer, chain printer etc
    • Non Impact Printer:- Non Impact printer does not involve striking the paper. Instead, they use ink sprayer toner powder.


Note:- The resolution of printer is measured in dpi (dots per inch). Laser printers are the example of page printer, and inkjet printers are the example of line printers.

Another type of printers available in the market

Label Printers are the smartest way to print labels one at a time. There are multi-purpose printers , that can print different types of labels. For example, label printers used in supermarkets can print bar codes as well as normal text. There are also some label printers that can print different sizes of labels on goods.
POS receipt and banking printers: these printers realize innovative technology and functionality to increase productivity, and reduce costs. A receipt printer plays an integral role in any POS (Point-of-Sale) system, signalling the cash drawer to open when the transaction is completed.
Plotter:- A plotter can be used to produce high quality, accurate and bigger drawings. They are usually used for computer aided design (CAD) and computer aided manufacture (CAM) applications such as printing out for houses or car parts. Plotters are available in two designs : Flatbed and drum.

Based on the hard copy and soft copy outputs, the output devices are classified into two types

  1. Hard copy
  2. Soft copy

Speaker:- A speaker is an output device that is used to play sound. Speakers allow you to hear sounds and music on computer.

Storage Device

  • Hard Disk:- A magnetic disk on which you can store computer data. Hard Disk is a computer main storage device and can hold more data and faster than other storage device. The hard drive was first introduced on September 13, 1956.
  • Floppy Disk:- A small, portable magnetic disk that is used to store and transport computer data. It is also known as a diskette. There are two type of floppy disk. 1. 3½ inch and it can hold 1.44 M.B data and 5¼ inch data and can hold 1.2 M.B data. First floppy was made by IBM.
  • Compact Disk (CD):- A CD known as optical disk. A compact disc, or CD, is an optical storage medium with digital data recorded on it. The digital data can be in the form of audio, video, or computer information. Firstly CD was introduced as Read Only device but now technology allow user to record data on it. A newer technology, the digital versatile/video disk (DVD). A CD was invented by James T. Russell in 1960. Some variations of the CD include:
    CD-ROM → WORM (Write once and read many) → CD-RW
  • Pen Drive:- A small portable USB flash drive consists of flash memory data storage device integrated with USB. A pen drive is a plug n play device known as USB flash drive, jump drive, thumb drive etc. The USB Flash Drive was introduced in 1996 and invented by Dov Moran

File Access on Disk

Disk Access time:- Disk operate in semi-random mode of operation and normally are referenced block wise. The data access time on disk consists of two main components:-
  • Seek Time:- Time to position the head on a specific track. On a fixed head disk it is the time taken by electronic circuit to select the require head while in movable head disk it is the time required to move the head to a particular track.
  • Latency Time:- The time required by a sector to reach below the read/write head.
    Disk Formatting:- Formatting is a three-step process that deletes all of your old data and prepares your entire disk for storing new data.
    • The formatting program removes the references to your old files. This makes the files inaccessible to most programs because the programs won't know where the files are located on the hard drive.
    • Disk is to divided into tracks and sectors.
    • A new file called a file allocation table is created. This file will be used to store the locations of data on the disk.

Booting Process:- All computers running Operating system share the same startup sequence:

POST (Power on Self Test):- When power is turned on POST programme start running. It is the diagnostic testing sequence that test a computer's basic input/output system. Then BIOS (or "starting program") runs to determine if the computer keyboard, random access memory, disk drives, and other hardware are working correctly and it start searching for operating system. First it search the floppy disk and then C: drive and If OS is found it start loading in the main memory.

Virtual memory:- Virtual memory is the use of space on a hard disk drive (HDD) to simulate additional main memory. Virtual memory permits software to run in a memory space (i.e., a logical memory) whose size is greater than the computer's RAM. Or you can say, if your computer lacks the random access memory (RAM) needed to run a program or operation, Windows uses virtual memory to compensate.

Cache memory:- Cache is the fastest memory and most expansive memory. It increases the efficiency of central processing unit. It lies between CPU and main memory. The CPU uses cache memory to store instructions that are repeatedly required to run programs, improving system speed. The advantage of cache memory is that the CPU does not have to use the motherboard’s system bus for data transfer.

The cache makes any data frequently used by CPU instantly available. If the required information is not located in the cache, a fetch is made from the main memory.

Generation of Computer:- (Hardware)

1st Generation (1940 - 1958) Vaccum Tube
2nd Generation (1959 - 1964) Transistors
3rd Generation (1965 - 1970) I.C (integrated circuit)
4th Generation (1971 - present) LSI (Large Scale integration),
VLSI (Very large scale integration)
ULSI (Ultra large scale integration)
5th Generation (today) Still under development phase

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