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Thursday, August 20, 2020

Computer Knowledge


Computer: It is a device that transforms data into meaningful & relevant information. Data can be anything like marks obtained by us in various subjects. It can be named, age, sex, weight, height, etc.

The computer can also be defined in terms of functions it can perform. A computer can:

  • accept data
  • store data
  • process data as desired
  • retrieve the stored data as and when required 
  • print the result in the desired format.

Computer Organization:

Fig: Block Diagram of Computer Organisation 

Functions of a Computer: 

The computer performs 5 major operations or functions irrespective of their size and make. They are:
  • it accepts data-instructions by way of input
  • it stores data
  • it can process data as required by the person (user)
  • it gives results in the form of output
  • it controls all operations inside a computer
This is the process of entering data & programs into the computer system.

Memory Unit:
It is used to store data & instructions which was given through input.

Types of Semiconductor memories:

RAM= Random Access Memory.
  • Read & Write Memory. 
  • The information stored in this memory can be erased & re-written.
  • Volatile memory.
  • Information stored in this memory will be lost when the power goes off.
ROM= Read-Only Memory.
  • Non-volatile memory.
  • Information stored in this memory will not be lost when the power goes off.
  • Writing into ROM is done once at the time of manufacturing.
  • It is programmed by the manufacturer.
  • We can't write information in this memory. 
PROM= Programmable Read-Only Memory.
  • It can be programmed by any user using the "PROM Programmer".
  • After the PROM is programmed, we can only read the information.
EPROM= Erasable Programmable Read-Only Memory.
  • Unlike ROM, PROM information stored in this memory can be erased & re-written.
  • Erasing is done by exposing to ultraviolet (UV) light for about 20 minutes.
EEPROM= Electrically Erasable Programmable Read-Only Memory.
  • Information stored in this memory can be erased electrically & re-written
  • After EEPROM is Programmed, we can only read info.

Differentiate b/w Primary Memory & Secondary Memory:

Primary Memory

Secondary Memory

Limited Memory

Vast/Large Memory



Made from Semi-conductor memories

Made from magnetic materials

Cost- High

Cost- Low

Arithmetic Logic Unit (ALU): The major functions performed by the ALU are; 
  • Addition (+), 
  • Subtraction (-), 
  • Multiplication (x)
  • Division (/)
  • logic & comparison
  • The process of producing results from the data for getting relevant & useful information.
  • ALU+CU-->CPU= Arithmetic Logic Unit & Control Unit of a computer system are jointly known as the Central Processing Unit.
  • CPU - the brain of any computer system.
Control Unit (CU):
  • The process of input, output, processing & storage is performed under the supervision of a unit called- "Control Unit".
  • It decides when to start the receiving data from outside, when to stop its system & where to store data, etc. 
  • It takes care of the step-by-step processing of all operations inside the computer.

Units of Computer Memory Measurements:

  • Bit (Binary Digit): A binary digit is logical 0 & 1 which represents a passive & an active state of a component in an electric circuit.
  • Nibble: A group of 4 bits.
  • Byte: A group of 8 bits. A byte is the smallest unit that can represent a data item or a character.
  • Word: A computer word- is a group of fixed numbers of bit processed as a unit that varies from computer to computer but is fixed for each computer. The length of a computer word is called word-size or word-length & it may be small as 8 bits (one Byte) or maybe as long as 96 bits.



1 Bit

Binary Digit

8 Bits

1 Byte

1024 Bytes

1 KB (KiloByte)

1024 KB

1 MB (MegaByte)

1024 MB

1 GB (GigaByte)

1024 GB

1 TB (Terra Byte)

1024 TB

1 PB (Peta Byte)

1024 PB

1 EB (Exa Byte)

1024 EB

1 ZB (Zetta Byte)

1024 ZB

1 YB (Yotta Byte)

1024 YB

1 (Bronto Byte)

1024 Bronto Byte

1 (Geop Byte)

Peripheral Devices:

Peripheral devices are connected to the computer externally. These devices are used for performing some specific functions. These are the following:
1.) Input devices, 2.) Output Devices, 3.) Peripheral Devices

Input Devices:

Input devices accept computing data & instructions from the user. The following are the example of various input devices, which are connected to the computer for this purpose. Eg. Keyboard, Touch screen, Mouse, Microphone for voice as input, Light Pen, Track Ball, Optic/ Magnetic Scanner.

  • It is the most common input device. Diverse kinds of keyboards are available, but they resemble each other with minor variations.
  • The keyboard is the most common use is- QWERTY board.
  • Generally, the standard keyboard has 104 keys.
  • In these keyboards, the cursor controls keys are duplicated to allow easier use of the numeric pad.

Mouse: An electromechanical, hand-held device.
  • It is used as a pointer.
  • It can perform functions like selecting the menu commands, moving icons, resizing windows, starting programs, & choosing options.
  • The uses of the mouse- an internal, magnetically coated ball, to detect the movement of the mouse across a flat surface, usually a desktop.
  • Nowadays Optical or laser mouse is used to detect the movement.
  • All windows based applications are designed to work with a mouse.
  • It is used to replace hard-to-remember key combinations with easier "Point & Click" actions.
  • It can't substitute all keyboard operations.
  • It can be an alternative for commands based operations.
Light Pen:
  • It works as a Light-sensitive detector to select objects on a display screen.
  • A light pen is similar to a mouse, except that with a light pen we can move the pointer & select objects on the display screen by directly pointing to the objects with the pen.

Optical Scanner:
  • These devices are used for automatic data collection.
  • The device of this category completely eliminates the manual input of data.
  • Image scanner: it translates printed images into an electronic format that can be stored in a computer's memory & with the right kind of software, one can alter a stored image. Eg. bar-code reader.
  • Optical Character Recognition (OCR): it used by banks to convert the scanned image of the typed or printed page into the text that can be edited on the computer. 

Touch Screen:
  • Touch panel displays & pads are now being offered as alternatives to the keyboard.
  • Here the input can be given through the computer screen, which accepts the input through the monitor.
  • The user touches electronic buttons displayed on the screen or they may use a light pen.

  • It takes voice as input.
  • The voice communication is more error-prone than information entered through the keyboard.
  • There are 2 types of microphones available: 1.) Desktop microphone, 2.) Hand-held microphone.

Track Ball:
  • A pointing device- a mouse lying on its back.
  • To move the pointer, we rotate the ball with our thumb, our fingers, or the palm of our hand.
  • There are usually one to three buttons next to the ball, which we use just like mouse buttons.
  • Advantages: Trackballs over the mouse is that is stationary so it does not require much space to use it.
  • We can place a trackball on any type of surfaces, including our lap.
  • For both these reasons, this is a popular pointing device for portable computers.

Output Devices:

Output devices return processed data (i.e information) back to the user. Some of the commonly used output devices are- Monitor (Visual Display Unit), Printers, Plotter, Speakers.
  • It is the most important output device because people interact with this device most intensively others.
  • Computer information is displayed, visually with a video adapter card & monitor.
  • Information processed within the CPU, that needs to be visually displayed, is sent to a video adapter.
  • The video adapter converts information from the format used, in the same manner as a television displayed sent to it by a cable service.
  • 2 basic types of monitors are used with microcomputers, which are the following: 1.) CRT, 2.) LCD.
CRT= Cathode Ray Tube.
  • It is the typical monitor that we see on a desktop computer.
  • It looks a lot like a television screen, & works the same way.

Liquid Crystal Displays (LCD):
  • Known as- Flat Panel Monitor.
  • Uses: to render images.
  • The statistic is the resolution of the monitor has a resolution of at least 800x600 pixels.
  • High-end monitors resolutions of 1024x768 pixels or 1280x1024 pixels.
  • Monitors are available in 2 kinds of resolutions: 1.) low resolution, 2.)high-resolution.


  • After the document is created on the computer, it can be sent to a printer for a hard copy (printout).
  • Some printers offer special features such as color & large page format. Some of the most commonly used printers are: 1.) Laser Printer, 2.) Ink-Jet Printer, 3.) Dot Matrix Printer, 4.) Line Printer. 
Laser Printer:
  • It produces a high-quality print that is normally found in publishing.
  • It is extremely fast & quiet (soundless).
  • Operation: easy with automatic paper-loading & no smudging or messing up of ink ribbons.
  • Capacity to print: up to 200 pages/ minute in monochrome (black & white) & up to 100 pages/ minute in colour.
Ink-Jet Printer:
  • It creates an image directly on paper by spraying ink through as many as 64 tiny nozzles.
  • The images it produces are not quite as sharp as the output of a laser printer, the quality of ink-jet images is still high.
  • It offers an excellent middle ground between dot matrix & laser printer.
  • Like a laser printer, the ink-jet printer is soundless & convenient, but not particularly fast.
  • It is more expensive than a dot-matrix printer. 
Dot Matrix Printer:
  • It was very popular at one point in time.
  • It is a very versatile & inexpensive output device.
  • In dot matrix printer the print head physically "hits" the paper through the ribbon & produces text (or images) by combinations of dots.
  • Speeds: measured by characters per second (CPS)
  • Less expensive, louder & produces lower print quality.
Line Printer:
  • It is used with large computer systems to produce text-based data processing reports.
  • It is high-speed printers with speeds ranging from 100 to about 3800 lines per minute.
  • Previously, print quality printers were not high.
  • Development in technology is improving print quality printers.
  • Price: cost range of lakhs rupees.


  • It is a special kind of output device that, like printer, produces images on paper, but does so in a different way.
  • It is designed to produce large drawings or images. Eg. Construction plans for building or blueprints for mechanical objects.
  • It can be connected to the port normally used by a printer.
  • It can draw curves by creating a sequence of very short straight lines.
  • It comes in 2 design: 1.) Flatbed, 2.) Drum
  • Flatbed: small size to be kept on the table with restriction of paper size.
  • Drum: big size using rolls of paper of unlimited length.


  • It allows us to listen to a voice like music & conversion with people.



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