What is a computer?

Computer is an electronic machine that accepts data as input and processes it using predefined instructions and gives output. Computers store and retrieve information using a variety of data storage devices such as HDD, SSD, CD, DVD, etc.

Modern computers can do more than trillions of calculations every second. Computers do many different jobs where automation is used. Some examples are controlling traffic lights, security systems, driver less cars, washing machines etc.

In other words we can say a computer is an automatic electronic device which can process, store and manipulate large volumes of data using predefined instructions with high speed and accuracy.

computer fundamental

Characteristics of a Computer

  • Speed : A Computer can perform difficult calculations and other processes at a high speed. It’s speed is measured in megahertz (MHz) or gigahertz (GHz). One megahertz equals one million ticks per second, and one gigahertz equals one billion ticks per second.
    (A single tick represents one hundred nanoseconds or one ten-millionth of a second. There are 10,000 ticks in a millisecond and 10 million ticks in a second.
  • Automatic : A Computer can perform all the operations automatically under the set of instructions given once.
  • Accuracy : A Computer performs every calculation with 100% accuracy. However , if a wrong input is given, it will produce wrong results. Computer works on GIGO principle, It means “Garbage In Garbage Out”.
  • Diligence : A Computer can perform a task repeatedly for an endless number of times with the same speed and accuracy. It does not suffer from tiredness, laziness or lack of concentration.
  • Versatility: A Computer is used to handle different types of jobs in different fields like engineering, medical, communication, shops, investigations, home and offices. It is also used for playing computer games.

History of computer

In ancient times, people use their fingers or even stones and sticks for calculations. They always feel that calculations are difficult. To solve that problem, people were trying to invent some machine or even devices for calculation.   


It is believed that the first calculating device was  Abacus. The exact origin of the abacus and who invented it is still unknown. Scientists found some evidence of using abacus in Europe, China, Japan and Russia around 2400 BC. It is constructed as a frame with beads sliding on wires. We find area wise different designs for abacus.  In Japan it is called “Sorobon”.


Napier’s bones

In 1617 John Napier introduced a calculating device called Napier’s bones. He was a great mathematician from Scotland. This device was made by using multiplication tables. Multiplication can be reduced to addition and division to subtractions.  

Napier’s bones

Calculation with Napier’s bones

425 x 6=?

 425 x 6 = 2550

Pascaline or Pascal’s Calculator

The Pascaline was designed and built by the French mathematician-philosopher Blaise Pascal. It was the first Mechanical Calculator. Pascal designed the machine in 1642. After trying 50 prototypes, he presented the device to the public in 1645. This machine was mainly for Addition and Subtraction but Multiplication and Division could be possible through repeated addition or subtraction. Its success story is behind its  carry mechanism, which adds 1 to 9 on one dial, and carries 1 to the next dial when the first dial changes from 9 to 0.

Pascaline or Pascal’s Calculator

How Pascaline work click here to watch video

Difference Engine

In 1819 English mathematician and computer pioneer Charles Babbage began to construct a computing machine called difference engine.He completed it by 1822 and displayed a small sample before the public on 14th June of the same year. It was a mechanical calculator. But it was not a general purpose calculator. It prepares numerical tables using a mathematical technique known as the method of difference. Today such types of tables are used for astronomical calculations. This same work is efficiently done by modern computers. But nearly a century and a half ago, the Difference Engine did much the same work, but slowly and mechanically.

Analytical Engine

The Analytical Engine was a mechanical general-purpose computer designed by Charles Babbage.It was first described by him in 1837 as the successor to his different engine. 

This machine was fully programmable and was able to perform any type of calculations. It consists of four components: the mill, the store, the reader, and the printer just like our modern computers. The mill was the calculating unit, similar to today”s central processing unit (CPU), and where data was stored was known as store, exactly like the memory and storage in modern computers; and the reader and printer were the input and output devices.The store was to be large enough to hold 1,000 50-digit numbers; this was larger than the storage capacity of any computer built before 1960.The reader was another new feature of the Analytical Engine. Data (numbers) were to be entered by punch card technique. 

Analytical Engine

Some consider Charles Babbage as Father of Computer, because he gave the idea of modern computers. His Analytical Engine contained all the features of today’s computer. 

After Babbage, different scientists and mathematicians worked on the development of computers and they invented different types of machines for calculations. Some of them are 

  • The Electronic Numerical Integrator And Calculator (ENIAC) 1943-46
  • The Electronic Discrete Variable Automatic Computer (EDVAC)- 1946-52
  • The Electronic Delay Storage Automatic Calculator (EDSAC) -1947-49
  • The Universal Automatic Computer (UNIVAC) -1951


All types of computers follow a basic principle


Computers first take the data as input, process it and give output as a result. During processing data stored in the computer memory.

Computer data means any kind of information. It includes text and numbers, pictures, sound, or video.

Data converts  into meaningful information after processing.

To perform all the above functions (input, process, output and storage) the computer needs it’s related Software and Hardware.


Computer software is a set of instructions that enable the user to interact with computer hardware. It also tells the computer what to do or how to perform a task.

We can classify software in the following categories.


System software or Operating System (OS) is designed in such a way that acts as an interface between the device and the user. It gives a platform for Application Software to run. System software is also used for making the computer personalize for users. Some examples for System Software are MS-DOS, Windows, Linux, Mac-OS, Android, Chrome OS etc.


Application software is a program designed for end users. Application Software needs a platform to run which is given by Operating System. Example of some Application Software are Writer, Calc, Excel, CorelDRAW, Ms-word,Tally, Photoshop, WhatsApp  etc.


Firmware is a software or set of instructions, programmed on a hardware device. It provides the necessary instructions to the device for how the device communicates with the other computer hardware. It permanently etched into a hardware device such as keyboards, hard drive, BIOS, mouse etc.


Computer hardware refers to the physical parts of a computer and related devices. The internal hardware parts are referred to as components, while external hardware devices are usually called peripherals.This includes the monitor, hard drive, memory, CPU,keyboard etc.

Hardware can be mainly categorized in the following way :


An input device is any hardware device that feeds data to a computer and allows you to control it.

Following are the examples for the input device


Keyboard is a basic input device for all digital computers. Nowadays different designs of keyboard are available in the market. The buttons of the keyboard are called the keys. 

The traditional keyboards have 104 keys, including A-Z alphabet, 0-9 numbers, 12 function keys, some symbols and special keys. Multimedia keyboards have some special keys to control audio and videos.

keyboard narmal
keyboard normal
keyboard multimedia
keyboard multimedia

Today, most desktop computer keyboards connect to the computer using either USB or Bluetooth for wireless communication. Before USB, a computer may have used PS/2 serial port.

Smartphones and tablets do not come with a physical keyboard. These devices utilize a on-screen keyboard to type text which is also called the virtual keyboard.

Now a days another types of keyboard is getting popularity, that is laser keyboard. This is not a physical keyboard. A device project laser light on a plane surface to create this type of keyboard. 

key pad


A computer mouse is a handheld hardware input device that controls a cursor in a GUI (graphical user interface) and can move and select text, icons, files, and folders on your computer. Mouse can be of following types


The mechanical mouse is one of the most traditional mouse in the history of computers. It is also known as a ball mouse because it uses a rubber ball to detect motion – That ball spins along as you move the mouse, and sensors will pick up on which direction you moved. This mouse had basically two buttons left and right.


This is the common mouse that you see everywhere these days. An optical mouse uses an LED and detects movement by sensing changes in the reflected light. This mouse is much more durable than mechanical mouse. This mouse have left and right click buttons with that a wheel for scrolling.


A wireless mouse, is also called a cordless mouse is a mouse that connects to a computer without the use of wires.. Usually, a USB receiver is plugged into the computer and receives signals from the cordless mouse.

wireless mouse
wireless mouse


A gaming mouse usually an optical mouse. Instead of having only three buttons like general optical mouse,  a gaming mouse have many buttons. These extra buttons are often programmable to do various things. Mostly for the purpose of gaming.



A trackball mouse is something like an upside-down ball mouse. Instead of moving the mouse around, it detects motion by spinning the ball. Even though it works similarly to the ball mouse, the design of the trackball mouse is totally different.



Presentation mouse is a kind of handheld wireless mouse use for PowerPoint presentation. It looks similar to a remote control. It has many buttons to control presentation properly and has a laser light too. 



A joystick is an input device commonly used to control video games. Joysticks consist of a base and a stick that can be moved in any direction. But digital joysticks have only buttons. It is also used as a flight simulator.


Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation. A scanner is connected to a computer through USB.  

There are different types of scanners:

Flatbed scanner – uses a flat surface to scan documents

Sheet fed scanner – like a laser printer where paper is fed into the scanner

Handheld scanner – the scanner is dragged over the page to be scanned

Card scanner – for scanning business card


The microphone is a computer input device that is used to input the sound. The audio signals are converted into digital data and stored in the computer. Because of artificial intelligence, now computers can recognize our voice and can get instructions from it. 


Magnetic Ink Card Reader (MICR)

MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank’s code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable.


Bar Code Readers

Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner.

Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer that the bar code reader is connected to.

Optical Mark Reader (OMR)

OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked. It is specially used for checking the answer sheets of examinations having multiple choice questions.


Mostly we all aware about this input device and its use. Touchscreen is an input device that allows users to interact with a computer using their fingers or stylus. They can be a useful alternative to a mouse or keyboard for navigating a GUI (graphical user interface). Touch screens are used on a variety of devices, such as computers, laptops, smartphones, and tablets.


A webcam is a camera that connects to a computer. It captures either still pictures or motion video and transfers it to the computer or computer network. 


A stylus is a pen shaped instrument with a round rubber piece that moves effortlessly across touchscreen devices like Mobile Phone, Tablet etc. 

Bio-metric devices

Bio-metric devices is an input device used to input bio-metric data into a computer. Here are the types of bio-metric devices:

Face scanner

Finger scanner


An output device is any hardware device that receives data from a computer and gives us an output in the form of text, image, video or audio.

Following are the examples for the output device


Monitor is the basic output device for any computer, where we can view the first output or result. The different types of monitors are

CRT( cathode ray tube )

CRT monitors are the very old version of monitor. The front screen of the monitor is made with glass, behind the there is a long narrow tube where cathode rays are reflected to create images. These monitors are very bulky in size and weight.electricity consumption also very high in this type of monitor.


LCD (Liquid Crystal Display)

LCD is a flat panel display technology. This type of monitor looks slim and light weight. It consumes much less electricity than CRT Monitors. Its picture quality is also better than CRT Monitor.


LED (Light Emitting Diode)

LED Monitor is almost similar like LCD Monitor. The only difference is the type of back lighting. LCD uses CCFL (cold cathode fluorescent lighting) and LED Monitor uses LED lights to illuminate the screen. But LED Monitor is much lighter in weight and slimmer than LCD Monitor.it consumes least electricity.


OLED (Organic Light Emitting Diode)

OLED is a new display technology that is brighter, more efficient and thinner than LED. this technology is mostly used for smartphones and tablets and expensive TVs. 



Speaker is another output device to give audio or sound as output. Headphones or earphones are also used in place of the speaker.

System Unit

System Unit is a metal box, which is the house for the major primary devices of any computer. This unit performs the majority of the functions that a computer is required to do. It includes 

  • SMPS
  • Motherboard
  • RAM
  • Storage Device (HDD, SSD, CD Rom etc)

    SMPS(Switch Mode Power Supply)

    SMPS(Switch Mode Power Supply) is a power supply unit(PSU) which regulates and adjusts the output voltage to computer acceptable range.


    Motherboard is a printed circuit board. It is the main board of the computer, which provides connectivity between all other hardware components.

    CPU  (Central Processing Unit)

    The Central Processing Unit is a principle part of any digital computer. It is also called the processor. It performs all types of data processing operations and controls all parts of the computer. That is why it is also known as  the brain of the computer. 

    CPU itself has following three components :

    • Memory or Register
    • Control Unit
    • ALU (Arithmetic Logical Unit)

    Memory Or Register : Memory or register is a small unit of data holding place. The CPU use register to temporarily hold processing information during the time of processing.

    Control Unit(CU) : The CU sends a control signal to the ALU so that the required operation can be performed properly.

    ALU (Arithmetic Logical Unit) : ALU performs all arithmetic and logical functions.

    Storage Devices

    Computer has two types of storage devices or memory.

    1. Volatile Memory
    2. Non Volatile Memory

    Volatile Memory(RAM)

    RAM (Random Access Memory) is called the volatile memory. It is called volatile because RAM stores the data temporarily. When the computer is switched off the data in it is completely erased. Some examples of RAM is SDRAM, DDR2 RAM, DDR3 RAM, DDR4 RAM etc.

    Non Volatile Memory

    Non volatile memory is the permanent memory of the computer. It includes HDD(Hard Disk Drive), SSD(Solid State Device), Flash Drive(Pen Drive), CD, DVD, Blu-ray Disk etc.

    HDD(Hard Disk Drive)

    An HDD is a data storage device that lives inside the system unit of a computer. It has spinning disks inside where data is stored magnetically. It is a permanent memory. 

    SSD(Solid State drive)

    A solid-state drive (SSD) is a new generation of storage device used in computers. SSD use flash-based memory, which is much faster than a traditional mechanical hard disk. Upgrading to an SSD is one of the best ways to speed up your computer.

    Flash Drive or Pen Drive

    Flash Drive or Pen Drive is a portable data storage unit. It connects to the computer through USB port. Pen Drive or Flash Drive is Fast and easy to transfer data . People use it to transfer data from one computer to another.

    CD, DVD, Blu-ray Disk

    CD, DVD, Blu-ray is a type of optical disk. Which is used to store high quality audio or Video files. These disks are removable and easy to carry. 

    The storage capacity of DVD is greater than CD and blu-ray is greater than DVD.

    Generation of Computer

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