Computer Devices

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As we have seen earlier that a computer consist of three parts

Input Device:- The device which is used to input Information into the computer are known as Input device. The physical components of computer are known as hardware. Some Input devices are given below in details.

Keyboard:- This is most commonly used input device. Its function is same like as typewriter. The keyboard is divided into few parts like Alphabet keys, Numeric pad, Function key, Special keys etc.

Mouse:- This is also called pointing device. This device is used for pointing the items on the screen. It can be moved on a smooth surface to simulate the movement of cursor that is desired on the display screen. Selection can be choose by simply pressing the button of mouse.

Scanner Scanner:- Scanners facilitate capturing the information and storing them in graphic format and displaying back on the graphical screen. Scanner consist of two components, the first one to illuminate the page so that the optical image can be captured and the other to convert the optical image into digital format for storage by computer. The graphic image scanned now can be processed directly by the computer.


Magnetic Ink Character Reader (MICR):- This device are generally used by banking industries to read the account number on chaques directly and does the necessary process.

Optical Mark Recognition (OMR):- This devises are capable for sense marks on computer readable papers. This kind of device is used by academic and testing institution to grade aptitude testes where candidates marks the correct alternative on a special sheet of paper.

Optical Mark Code Reader (OBR):- This device are used to scan a set of vertical bars of different width for specific data and are used to read tags and merchandise in stores, medical records, library books etc.

Joystick:- Joystick is mainly used with computer games. It is in the form of rigid rod, which can moved left right up or down as required to move the cursor.



Storage device:- A storage device in the computer is required for storage and retrieval of the instructions and data . There are verity of devices used for storing data. A storage system can be classified mainly in three parts-

Internal processor memory:- These are consist of the small set of high speed registers which are internal to a processor and are used as temporary locations where processing is done.

Primary Memory:- Primary memory consist of semiconductor memory chips and is used to store the data and programs currently in use. Each storage cell can be directly accessed without affecting any cells hence it is also called Random Access Memory (RAM). 

  • ROM- Read Only Memory - It is another type of main memory. this can be used for storing programs provided by the manufacturer. ROM's can be written only the time of manufacture. 

Secondary Memory:- As discussed above all the memories are volatile memory, which works only in the present of electricity. We need a permanent storage devices which would be reliable and less expensive. Thus we get that magnetic ink coated materials are less expensive and they are having long life. Some of the secondary storage devices are Magnetic Tape & Magnetic Disks.

Magnetic Tape:-   It looks same like as tape recorder. It is mainly used for keeping backup of data. This tape may be 12.5 to 25mm wide and it's length may be 500 meters to 1200 meters. File accessing mode of this device is serial accessing.  These are cheaper since these are removable from the drive, they provide ultimate storage capacity. These are not suitable for on-line retrieval of data since sequential searching will take long time. They are low coast, low speed, portable and are still widely used because of their low coast.

Magnetic Disks:- Magnetic disk is a circular platter of plastic, which is coated with magnetic material. A conducting coil named as 'Head' is used for the job of reading and writing on the magnetic surface. There are two widely used Magnetic Disks

  1.  Floppy Disks
  2. Hard Disk or Winchester Disk

Floppy Disks:-A floppy disk is made of a flexible thin sheet of plastic material with a magnetic coated and grooves arranged in concentric circles called Tracks. Floppy is a very good medium for transferring data from one location to another. There are two types of floppy disk available today

  1. 5 Inches

  2. 3 Inches

A floppy disk divided into Track & Sectors

5 floppy:- this floppy looks too much bulky due to its size. It has the capacity of 1.2 MB or 360 KB. It consist with 40 track and 9 sectors. 

3 Inches floppy:- This floppy have the capacity of 1.44 MB. It consist with 80 tracks and 15 sectors.


Hard Disk:-This is the most useful for storing large volume of information. It is consist of two or more magnetic plates fixed to a spindle, one below the other with the set of read/write head. The disk is pack in permanently sealed inside a case to protect it for dust. It's rotation speed is typically 3600rpm. This high speed of rotation ensure that all areas of the disk appears under the read/write head very frequently. Its size of storage capacity vary from 20 MB to 10 GB.

Figure: Hard disk layout

Output Device:- This device is used for output the result or process to either on display device or  to paper. the various output device are given below.

Monitor:- This is the most commonly used output device. It is also known as VDU (Visual Display Unit). It is CRT (Cathode Ray Tube) display Device. Its text mode contains 25 rows and 80 columns but graphic mode contains 640 pixels from left to right and 480 pixels from up to down. Monitor itself can be classified in following categories

  • Monochrome ( Black & White)
  • CGA ( Color Graphics Adapter)
  • EGA ( Enhanced Graphics Adapter)
  • VGA (  Video Graphics Adapter)



Figure: VGA Monitor

Printer:- This device is used for producing text or graphics printout to the paper. This is divided in two category

Impact Printer:- The printer whose head is directly in touch of paper is known as Impact printer. e.g.  

  1. Dot Matrix Printer:- These printers are of low coast. This printer uses the technology of moving head upon a inked ribbon and paper. It's quality is not so fine.
  2. Line Printer:- This printer prints one line at a time.
  3. Daisy wheel printer
  4. Plotter:- This printer is used for taking printout of graphs.

Non-Impact Printer:- The printer whose head is not directly in touch of paper are known as Non-impact printer. e.g.

Inkjet Printer:-These printers print the images to the paper by spraying controlled stream of tiny droplets on the paper. This is very silent and high quality printer.


 HP Deskjet Printer
HP Laser Printer

Laser Printer:- This is a very high speed, high volume and high quality technology. Printing is achieved by deflecting laser beams on the photosensitive surface of a drum and the latent image attract the toner to the image area.


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