OVERVIEW OF COMPUTER-Karnataka 1st PUC Computer Science Study Materials





“Computer is an electronic machine that can store, recall and process data. It can perform tasks or complex calculation according to a set of instructions or programs.

How does the computer work?

It is as simple as making tea. To prepare tea, we add water, tea powder, milk, and sugar. These are all considered as input. After adding all, we have to boil. That boiling is called processing. After boiling, we get tea. That is called output.


Similarly, the computer works based on the input, processing and output.


Input-Process-Output cycle (IPO Cycle)

Characteristics of Computer:

· Speed

· Storage

· Accuracy

· Diligence


· Versatility

· Flexibility

· Cost effectiveness

The computer works very fast. The speed of Computer is measured in terms of MIPS (Million

Instructions Per Second) or BIPS (Billion Instructions Per Second).

For Example A money counting machine counts money faster than man.


The computer can store a large volume of data and information. The storage capacity of the computer is measured in terms of Bytes. A group of 8 Bits is called a Byte.


The computer generated results are exact and without any mistakes with high rate of consistency.


Unlike human beings, a computer does not suffer from limitations like tiredness and lack of concentration. It can work for hours without making any errors.


Computers are capable of performing any task. Multi-processing features of computer make it quite versatile in nature. The computer can be adapted to any field easily. It is used for scientific calculations, business processing, for playing games, teaching, training etc.


Flexibility would involve the number of things you can do with a computer. While some are best used for simple business tasks, and filing of tasks, others are good for multimedia, gaming, and so on.

Cost effectiveness

Computers reduce the amount of paper work and human effort, thereby reducing costs.

Components of Computer system:

There are four components in the computer system. They are:

¨ Hardware

¨ Software

¨ Data & Information

¨ User(s)


The physical parts of a computer system called as hardware. The hardware components can be seen, touch and feel. The hardware components are fixed inside or outside the computer system.

Example Keyboard, Mouse, Monitor, Printer, RAM, CPU etc.


A Set or collection of programs is known as software. The software is a computer program written using some computer programming languages to operate the computer. Software tells the hardware what to do. Unlike hardware, we can’t touch the software.

Example Operating System, TUX Paint, Office Packages, Nudi, Adobe Reader, Computer Games etc.

The software is broadly classified into two types. They are

1. System Software: It is a type of computer program that is designed to control and work with computer hardware, to run a computer's hardware and application programs.

Example: Microsoft Windows, Linux, DOS etc.

2. Application software: It is a type of Software written by the user to perform a particular task like drawing a picture, playing computer games.

Example: Paint, Nudi and Office Package etc.

¨ Difference between Hardware and Software



Physical components of a computer are called Hardware.

Set of programs is called Software.

Hardware can touch, see and feel.

The software can not touch and feel.

Constructed using physical materials or components.

Developed by the programming language.

Not affected by computer viruses.

Affected by computer viruses.

User cannot make copies

User can make copies

Example: Monitor, Keyboard, RAM

Example: OS, Text Editor, Nudi


Data is a collection of unprocessed items, which can include text, numbers, audio or video. Data is the raw information or basic facts that computer can process.

For Example: “PARAM” 16

The computer processed data is called information, which gives particular meaning.

For Example: Name=“PARAM” Age=16.


People who use the computers are called users. These computer operators are called computer users.

Functional components of a computer:

  • Basically any computer is supposed to carry out the following functions.
  • Accepts the data and program as input.
  • Stores the data, program and retrieve as and when required.
  • Process the data as per instructions given by the program and convert it into useful information.
  • Communicate the information as output.

Block diagram of a computer

A computer is designed using four basic units. They are:

1. Input Unit

2. Central Processing Unit(CPU)

· Control Unit

· Arithmetic and Logic Unit (ALU)

3. Memory Unit

4. Output Unit

Control Unit

Input Unit Output Unit

Arithmetic & Logic Unit


Memory Unit

Primary Memory

Secondary Memory


 Input Unit

Computers need to receive data and instructions in order to solve a problem. The Input unit performs this operation. The Input Unit basically links the external world or environment to the computer system. The input unit may consist of one or more input devices. The Keyboard and mouse of a computer are the most commonly used input devices.

¨ Central Processing Unit (CPU)

It is the main part of a computer system like the heart of a human being. Most computers are identified by the type of CPU that is present in them. The function of the CPU is to interpret the instructions in the program and execute them one by one. It consists of two major units.

1. Control Unit: It controls and directs the transfer of program instructions and data between various units. The main activity is to maintain order and direct the operations of the entire system.

2. Arithmetic and Logic Unit (ALU): Arithmetic and Logic Unit performs arithmetic and logical operations and controls the speed of these operations. Arithmetic operations like addition, subtraction, multiplication and division (+,-,*, /) and logical operations like AND, OR, NOT and relational operations like (<,>, <=,>=) are being carried out in this unit.

¨ Memory Unit

The data and the instructions required for processing have to be stored in the memory unit before the actual processing starts. In a similar manner, the results generated from processing have to be preserved before it is displayed. The memory units thus provide space to store input data, intermediate results and the final output generated.

Secondary storage devices are additional memory (storage) devices such as floppy disks, magnetic tapes, Hard Disk Drive (HDD), Compact Disk (CD), Digital Versatile Disk (DVD) etc., which are used to store huge information for future use.

Note: The input unit, an output unit, and secondary storage devices are together known as

Peripheral Devices.

¨ Output Unit

It is used to print or display the results, which are stored in the memory unit. The actual function of the output unit is just the reverse of the input unit. Thus, the output unit links the computer to the outside world. The Monitor and Printer are the most commonly used output devices.

Evolution of computer:


Approximately 4,000 years ago, the Chinese invented the Abacus. It was the first machine used for counting and calculating. It is made of a wooden frame, metal rods, and wooden beads Abacus was mainly used for addition, subtraction and later for division and multiplication. Today, the abacus is still used widely in China and other Asian countries to count and calculate, just as we use calculators.

Napier’s bones

In the early 17th century, John Napier, a Scottish mathematician, invented another calculating tool. “Napier’s bones” was based upon manipulation of rods with printed digits. The rods were made of bone, ivory, wood or metal. The set consists of 10 rectangular blocks with multiples of a different digit on each of the four sides.

The slide Rule

The slide Rule was invented by William Oughtred. It is based on the principle that acutal distance from the starting point of the rule is directly proportional to the logarithm of the numbers printed on the rule. The slide rule is emboided by the two sets of scales that are joined together, with a marginal space between them.

Adding Machine-Pascaline

In 1642, at the age of 19, a French mathematician by the name of Biaise Pascal invented the Pascaline. The Pascaline is known as the first mechanical and automatic calculator.

The Pascaline was a wooden box that could only add and subtract by means of a series of gears and wheels. It had a box with eight movable wheels called dials. When each wheel rotated one revolution, it would then turn the neighboring wheel.

Leibniz Calculator

Mathematician Gottfried Leibniz built a calculator in 1650 that could add, substract, multiply and divide the numbers.

Jacquard loom

In 1801, Joseph Mary Jacquard invented the Jacquard loom. A poweed loom that used punched wooden cards to automatically weave incredibly detailed patterns including pictures and text. This can be taken as the first “Read only Memory” device.

 Difference and Analytical Engine

In the early 1820s, an English mathematician by the name Charles Babbage designed a computing machine called the Difference Engine. This machine was to be used in the calculating and printing of simple math tables. In the 1830s, he designed a second computing machine called the Analytical Engine. This machine consited five units, which became the basic principle for the development of modern computer. Hence Charles Babbage is known as the "Father of Computers”.

1833-First Programmer

Lady Ada Lovelace was a first computer programmer, who designed program for Babbage’s Analytical Engine.

1890 AD – Hollerith Tabulating Machine

In 1889, an American named Herman Hollerith invented a counting machine to count the population of USA. This electronic machine is able to read the information on the punched cards and process it electronically. Herman Hollerith was the founder of the company than became famous as IBM.

Generations of Computer

Depending on the development of the technology the generation of computer is classified into five generations.

· First Generation of Computer (1940-1956)

1. The first generation of computers is started with using vacuum tubes as the basic components.

2. The speed of these computers was very slow, storage capacity was very less and these computers are large in size.

3. This generation computers operated only on machine language.

4. Input was based on punched card, paper tapes an output was obtained as printout.

Some computers of this generation were ENIAC (Electronic Numerical Integrator and

Calculator), UNIVAC (Universal Automatic Computer).


· It stands for Electrical Numerical Integrator and Computer.

· It used a word of ten decimal digits instead of binary ones like previous automated calculators /computers.


· It stands for Electronic Discrete Variable Automatic Computer.

· It was to be a vast improvement upon ENIAC. Mauchly and Eckert started working on it two years before ENIAC even went into operation.

· This idea was to have the program for the computer stored inside the computer.


· Universal Automatic Computer was the first commercial computer produced in the United States.

· Second Generation of Computer (1956-1963)

1. In this generation transistors were used in place of vacuum tubes.

2. These machines were much faster, more reliable than their earlier machines.

3. It generates less heat and consumed less electricity as compared to first generation computers.

4. Second Generation computers used punched cards for input and printout for output.

5. This computer moved from the use of machine language to assembly languages.

6. The computer stored their instructions in their memory, which moved from magnetic drum to magnetic core technology.

Some computers of this generation were IBM 1620, IBM 7094, CDC (Control Data Corporation) 1604 and 3600, and UNIVAC 1108.

· Third Generation of Computer (1964-1971)

1. In the third generation of computer Integrated Circuits (IC's) were used in place of transistors.

2. In this generation, Keyboard and monitors were used instead of punched cards and printout.

3. These IC’s were increased the speed of processing and storage capacity.

4. These computers were more reliable, smaller in size and faster.

5. Maintenance cost was low comparing to the previous generation and consumed less electricity.

Some computers of this generation were IBM-360 series, Honeywell-6000 series, PDP (Personal Data Processor), IBM-370/168.

· Fourth Generation of Computer (1971-1980)

1. In the fourth generation of computer, microprocessors were used in place of Integrated Circuits(IC’s).

2. The fourth generation of computers is marked by the use of Very Large Scale Integrated (VLSI) circuits.

3. This made computers smaller in size became more powerful, they could bi linked to form network.

Some computers of this generation were Mini Computer and Mainframe computer, Personal computers.

· Fifth Generation of Computer (1980-till date)

1. Fifth generation computer involves the concept of Artificial Intelligence (AI) which made the computer think like human beings.

2. This generation uses VLSI Integration) technology.

(Very Large Scale integration) and ULSI (Ultra Large Scale

3. These computers are more intelligent and faster comparing to other generation computers.4. Types of this generation computers are Desktop, Laptop, Notebook, and Robot. etc.


Classification of Computer:


· Classification based on Purpose

According to purpose, computers are classified into general purpose and specific purpose. General purpose computers are designed to perform a range of tasks. They have an ability to store numerous programs but lack in speed and efficiency. Specific purpose computers are designed to handle a specific problem or to perform a specific task.

· Classification based on Principles of Operation

According to principles of data handling, computers are classified into three types

1. Analog Computers

2. Digital Computers

3. Hybrid Computers

Analog Computers

Analog computers work upon continuous data. Analog computer operates by measuring rather than counting. The analog computers are that all calculation take place in parallel, hence faster. Modern analog computers usually employ electrical parameters, such as voltages, resistances or currents, to represent the quantities being manipulated. Computations are carried out with the physical quantities, such as voltages, length, current, temperature etc. The device that measures such quantities are analog devices.

Digital Computer

The digital computer works upon discontinuous data. A digital computer operates on digital data such as numbers. It uses binary number system in which there are only two digits 0 and 1. Each one is called a bit. They convert the data into digits (Binary Digit 0 and 1) and all operations carried out on these digits at extremely fast rates. A digital computer basically knows how to count the digits and add the digit. Digital Computers are much faster than an analog computer and far more accurate. Computers used for business and scientific applications are digital computers.

Hybrid Computers

Hybrid computer are the combination of both analog and digital computer. They accept both the analog and digital data for processing. Hybrid computers incorporate the measuring feature of an analog computer and counting feature of a digital computer. For computational purposes, these computers use analog components and for storage, digital memories are used.

Now-a-days analog- to- digital computer (ADC) and digital-to analog computer(DAC) rare used to transforming data into suitable form.

In these computers, some calculations take place in analog manner and rest of them takes place in a digital manner. Hybrid computers are best used in the hospital where the analog part is responsible for measurement of patient’s heart beat, blood pressure, temperature and other vital signs and then the operation is carried out in a digital fashion to monitor patient’s vital signs. Hybrid Computers are also used in weather forecasting.

 Differences between Analog & Digital computers

Analog Computer

Digital Computer

Operates on continuous values of data

Operates on discrete values of data

They give only approximate results

They give accurate results

Processing is slow

Processing is fast

They have very limited use

They are versatile

They have small memory & less reliable

They have large memory & more


· Classification based on Configuration

Based on the performance, size, cost, capacity, the digital computers are classified into four types:

1. Micro Computers

2. Mini Computers

3. Mainframe Computers

4. Supercomputers

Micro Computers

1. Also, know as PC (Personal Computer), it was introduced in 1970.

2. The number of processors in microcomputers will be one or two processors.

3. It contains input devices, output devices, storage device and processor.

4. The number of processor will be one or two. It is used by one person at a time.

5. Example: Desktops (PC, Macintosh), Laptops, Notebooks, Tablets, Palmtops, Smart Phones.

Uses of Micro computers

· They are used as desktops either in offices or even in homes.

· Children enjoy playing games & watching movies in these computers.

· They are cheap and user-friendly.

· Their operation can be easily learned by anyone having the logical aptitude.

¨ Mini Computers

1. Mini computers were introduced in the 1960’s.

2. Minicomputer is larger and more powerful than personal computer.

3. In can execute five million instructions per second.

4. It generally consists of two or more processors.

5. Minicomputer can serve up to 4000 connected users simultaneously.

6. It is normally accessed by users via personal computer or terminal. A device with a monitor and keyboard is called terminal.

7. It is also known as dumb terminal. It has no processing power and cannot work as stand-alone computer.

8. Example: Digital Alpha, VAX-800, AS 400

Uses of Mini computers

· They are often used by small and medium sized companies to provide centralized store of information.

· They are used for data processing.

 Mainframe Computers

1. Mainframe computers were introduced in 1975.

2. It is very large computer in size.

3. It is more powerful than mini computers and consists of multiple processors.

4. It is designed to perform multiple tasks for multiple users at the same time.

5. The user access a mainframe computer through personal computer.

6. It can execute 16 million instructions per second.

7. Example: CDC 6600, NEC 610, DEC 10

Uses of Mainframe Computers

· Mainframe computers are used in large organizations.

· They are big computer systems sensitive to temperature, humidity, dust etc.

· Qualified & trained operators are required to operate them.

· They have a wide range of peripherals attached.

· They have large storage capacity.

· They can use a wide variety of software’s.

· They are not user-friendly.

· They can be used for more mathematical calculations.


1. Supercomputers were introduced in 1980. Super computer is the fastest computer.

2. Supercomputer is the biggest in size and the most expensive in price than any other computers.

3. Supercomputer is the most sophisticated, complex and advance computer.

4. It has a very large storage capacity.

5. It can process trillions of instructions in one second.

6. Supercomputers are used for highly calculations intensive task.

7. Supercomputers are designed for ultra-high performance tasks such as weather analysis, encryption cracking, and the creation of animation.

8. Example: IBM Roadrunner, IBM Blue Gene, PARAM Padma, etc.

Uses of Supercomputers

· Weather Forecasting

· Animated Graphics like Hollywood Movies

· Nuclear energy research

· Space Science

· Weapons and Missile design

· Petroleum Exploration etc.

Supercomputing in India

India's supercomputer program was started in the late 1980s because Cray supercomputers were denied for import due to an arms embargo imposed in India, as it was a dual use technology and could be used for developing nuclear.

PARAM 8000 was India's first supercomputer. It was indigenously built in 1990 by Centre for

Development of Advanced Computing and was replicated and installed at ICAD Moscow in 1991 under Russian collaboration.




Bhabha Atomic Research Centre (BARC)


Indian Space Research Organization (ISRO)


Computational Research Laboratories


Physical Research Laboratory


Centre for Development of Advanced Computing

Applications of computers:

  • Schools and colleges
  • Banks
  • Office
  • Stock control in business firms
  • Stock exchange
  • Research and developments
  • Entertainment and news
  • Government office
  • Satellite communication
  • Publishing
  • Travel
  • Computer-aided manufacturing (CAM)
  • Hospital.


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