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Computers

 

Computer

The word computer has originated from the Latin word Compute.

Compute means to calculate.

Computer is an electronic device.

It executes the instructions in a program.

Computer after data input, processes the data, produces output and stores the results.

Components of a computer

Input unit - It accepts data and instructions from the user.

It converts the accepted instructions into the machine language.

It gives converted instructions to CPU for processing.

Input devices:

Common input devices - Keyboard and Mouse

Track Ball

It is used as an alternate of mouse. The user moves its ball. This moves the pointer on the screen.

Joystick

Input device which moves the cursor on the screen.

Widely used in Computer games

Digital camera

Digital camera captures images and records the videos. These are stored in files. These pictures, images and videos can be edited and copied on to computers.

Microphone

Microphone is an input device for sound. It converts sound into electrical signals.

Voice recognition software can be used to enter text in word processor application by using the microphone.

Touch screen

Touch screen is an input and output device and also a display screen.

On the screen text or pictures are displayed.

A user interacts by touching the screen.

When a touchscreen is used there may be no requirement of keyboard or screen.

These are widely used in smart phones, ATM machines and other equipments.

Digital Video

Digital Video stores images from video camera or television in a digital format. Digital videos are preferred over analog videos. And used in multimedia presentations.

Scanner

An image scanner is an electronic device.

It optically scans images, object, text, pictures or handwriting and converts it to a digital image. 

It is similar to photocopier machine but makes digital copy of an image.

Graphic tablet

graphic tablet is a computer input device

A user can write text, draw pictures, images, animations and graphics, with a special pen like input device.

Keyboard

Keyboard is the most commonly used input device in computer.

There are three types of keys on the keyboard

Alphanumeric keys, special keys and function keys.

Alphanumeric keys

Alphabets from A to Z

Digits  - 0 to 9

Different characters such as space.

Special keys include

alt

backspace

caps lock

ctrl

delete

enter

shift, etc.

Function Keys

Keys from F1 to F12 in the keyboard

Mouse

An electronic input device.

Mouse controls the movement of the cursor or pointer on a display screen.

Mouse - without cord or wire is called a wireless or cordless mouse.

Output unit

It accepts processed data from CPU. It converts results from machine language into simple language and displays results to user. It prints results on paper or other permanent media.

Types of output

Hard copy Printed on paper –Hard Copy

Displayed on screen – Soft Copy

Output Devices 

The means through which computer gives output are known as output devices

Common Output Devices

Monitor

Display screen of computer.

Visual Display Unit of Computers

Printer

Printer is an external hardware or output device.

Printer gives the output in printed format (usually on paper) after receiving data from computer

An external device used with computer that prints image, text or photo.

Types of printers

Daisy-Wheel

Dot-Matrix

Ink-Jet

Laser

LCD& LED

Thermal Printer

Speed of printers in measured in

cps - characters per second 

ppm- pages per minute

 

Projector

Projector is that hardware and output device

It projects an image on the flat surface like computer screen.

Projectors are commonly used in presentations, meetings, seminars education and training.

Sound card

Also known  audio card .

 Sound card enables computer to produce sound through speaker or head phone.

Speaker

It is a hardware device.

Speaker presents the sound produced during any program.

This is connected to sound card.

Video Card or Graphics Cards

This is an internal circuit board

It allows the image to be displayed on the monitor.

Memory unit

It temporarily or permanently holds the data received from the input device.

It holds the data being processed and intermediate results being generated.

It holds the system software and the application software in use.

Computers memory is mainly classified into two types.

Random Access Memory

All active programs and data are stores in RAM

They may readily available and easily accessed by the CPU.

Read Only Memory

The data stored on ROM cannot be changed.

It is non-volatile.

ROM can keep its contents even without a power source.

The number of bytes it can store determines the storage capacity of a memory.

Computer storage

It is measured in Bytes

Kilobytes (KB)

Megabytes (MB)

Gigabytes (GB)

Terabytes (TB)

1 kilobyte is - 1024 bytes

1 megabyte - 1024 kilobytes

1 gigabyte - 1024 megabytes

1 terabyte - 1024 gigabytes

Write Time

The time taken to write a word.

Access Time of the Memory

The time to retrieve information

Secondary / Auxiliary storage

Auxiliary storage holds what is not currently being processed.

It is used for input-data and programs.

Magnetic tape

It is a magnetically coated strip of plastic.

It is data storage medium.

Tapes are sequential-access media

Floppy disk

It is a flexible circular disk of diameter 3.5 inches.

It is made of plastic coated with a magnetic material.

Hard Disks

Hard disks have large storage capacity.

These are rigid and less portable than floppies and disks

These are found in desktops computers and laptops.

They are less portable than floppies

Zip disk

They are slightly larger than the conventional floppy disks and can hold 100 MB of data

Jaz Disk

They are removable disk drives and can hold 1 GB of data

Optical Disk

They are storage medium.

From these data is read and to which it is written using lasers.

They can store much more data up to 6 gigabytes than magnetic media as floppies and hard disks

CD-Rom

It is a type of optical disk .

It is capable of storing large amounts of data up to 1 GB

They cannot be erased and filled with new data after it is once recorded.

DVD

DVDs are digital versatile disks.

They are the high density disks

Can hold upto 17 GBs of data on both its platters.

Central processing unit

The entire works get done in the CPU - Central Processing Unit and it is also known as the brain of computer.

It controls all the parts of computer system.

CPU is further classified into two components

1.   ALU - Arithmetic and Logical Unit

It is the part that executes the computer’s commands

The ALU can only do one thing at a time but can work very fast

2.   Control Unit

This is the part of the CPU

It controls the machine cycle.

It directs the operation of the processor.

It takes numerous cycles to do even a simple addition of two numbers.

 

Types of Computer

Based on uses

Computers can be classified based on their uses.

Analog computers

It measures pressure, temperature, length etc of physical quantities and converts into its numerical value.

They are mainly used for scientific and engineering purposes

Digital computers

It is used in counting of words, numbers, or other special symbols

It is also used in banking processes.

 Hybrid computer

It is a combined form of analog and digital computer.

Informations are continuously converted into data that are received in the form of input.

Output may be in form of analog and digital.

They are used in machines and factories.

Based on sizes

Micro computers

Micro computers are the smallest computer in which ALU and CPU are based on the same chip.

Personal computer

It is single user system.

Used generally for personal and simple business needs.

Mini computer

Mini computers are more powerful than micro computers

Many users can access the computer at the same time.

It processes data very fast and quickly.

Mainframe computers

They are giant in size and of highly storage capacity.

They can process a substantial large amount of data very rapidly

They are used in banks, large organizations and public sectors institutions.

Super computers

Super computers are capable of processing the huge amount of data in fraction of seconds.

They are used in very complex calculations.

The application of space shuttle or a satellite launcher is controlled by the super computers.

In India super computers are used for weather forecasting departments and other leading research institutions.

Computers Awareness For Competitive Exams Competitive and Entrance Examinations

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