In this lesson, we present an overview of the basic design of a computer system: how the different parts of a computer system are organized and various operations performed to perform a specific task. You would have observed that instructions have to be fed into the computer in a systematic order to perform a specific task. Computer components are divided into two major categories, namely, hardware and software. In this lesson we will discuss about hardware, i.e., the machine itself and its connected devices such as a monitor, keyboard, mouse etc., as well as software that makes use of hardware for performing various functions.


The computer is an electronic device that stores, retrieves, and processes data, and can be programmed with instructions. A computer is composed of hardware and software and can exist in a variety of sizes and configurations. The computer has moved through various stages of development and improvement. These states are referred to as generations of computer.

Computer Applications

To begin with, you must understand the impact of computers in the world today. The computer is affecting our lives in one way or the other. Airlines, railways, reservations, telephone and electricity bills, banking, medical diagnoses, weather forecasts etc. the list of the services using a computer is almost endless

You would have probably notice that some applications of computers have made life much easier for you- your air ticket is now issued in a matter of minutes and your credit card is processed very fast. You may be surprised to know that the computer cannot perform any task without you. The computer needs to be instructed on exactly what is has to do.


The computer’s characteristic as high speed of calculation, diligence, accuracy, reliability, or versatility has made it an integrated part in all business organizations.

Computer is used in business organization for:

  • Payroll Calculations
  • Budgeting
  • Sales Analysis
  • Financial forecasting



The computer has provided a lot of facilities in the Education System.

  • The uses of computer provide a tool in the Education system known as CBE (Computer Based Education).
  • CBE involves Control, Delivery and Evaluation of learning.
  • The computer education is very familiar and rapidly increasing the graph of computer students.
  • There are number of methods in which educational institutions can use computer to educate the students.
  • It is used for prepare a database about student performance and analyses are carried out.

Engineering Design

Computers are widely used in engineering purposes.

One of major areas is CAD (Computer aided design). CAD provides creation, edition, and modification of image. Some fields are:

  • Structural Engineering: Requires stress and strain analysis required for design of Ships, Buildings, Budgets, Airplanes, etc.
  • Industrial Engineering: Computers deal with design, implementation and improvement of integrated systems of people, materials and equipment’s.
  • Architectural Engineering: Computers help in planning towns, designing buildings, determining a range of buildings on a site using both 2D and 3D drawings.


Health Care

Computers have become important part in all Medical Systems. Computers are being used in hospitals to keep the record of patients and medicines. It is also used in scanning and diagnosing different diseases. ECG, EEG, Ultrasounds and CT Scans, etc., are also done by computerized machines.

Some of major fields of health care in which computers are used:

  • Diagnostic System: Computers are used to collect data and identify cause of illness.
  • Lab-diagnostic System: All tests can be done and reports are prepared by computer.
  • Patient Monitoring System: These are used to check patient’s signs for abnormality such as in Cardiac Arrest, ECG, etc.
  • Pharma Information System: Computer checks Drug-Labels, Expiry dates, harmful drug side effects, etc.


Today Banking is almost totally dependent on computer. Banks provide following facilities:

  • Banks on-line accounting facility, which includes current balances, deposits, overdrafts, interest charges, shares and trustee records.
  • ATM machines are making it even easier for customers to deal with banks.

Features of Computer

Man developed computers so that it could perform intricate operations such as calculation and data processing or entertain him. Today, computers are everywhere in our offices, homes, appliances and automobiles the list is endless. Much of the world’s infrastructure runs on computers, and the computers have profoundly changed our lives, mostly for the better. Let us discuss some of the features of a computer, which make it an essential part of every emerging technology and such a desirable tool in human development.

  • Speed: The computers process data at an extremely fast rate, i.e. at millions or billions of instructions per second. In a few seconds, a computer can perform a huge task that a normal human being may take days or even years to complete. The speed of a computer is measured in megahertz (MHz), that is, one million instructions per second.
  • Accuracy: Besides being efficient, the computers are also very accurate. The level of     accuracy depends on the instructions and the type of machines being used.

Since we know that the computer is capable of doing only what it is instructed to do, faulty instructions for processing the data automatically lead to faulty results. The faulty results due to faulty instructions or incorrect input data are known as GIGO, that is, garbage in garbage out.

  • Reliability: Generally, reliability is the measurement of the performance of a computer, which is measured against some predetermined standard for operation without any failure. The major reason behind the reliability of the computers is that, at hardware level, it does not require any human intervention between its processing operations. Moreover, computers have built-in diagnostic capabilities, which help in continuous monitoring of the system.
  • Storage Capability: Computers can store large amounts of data and it can recall the required information almost instantaneously. The memory of the computer is relatively small and it can hold only a certain amount of information. Therefore, the data are stored on storage devices such as magnetic tape or disks. The data from these devices can be accessed and brought into the main memory of the computer, as and when required, for processing.
  • Versatility: Computers are quite versatile in nature. They can perform multiple tasks simultaneously with equal ease. For example, at one moment it can be used to prepare a letter, at the other moment it can be used to play music and in between one can print a document as well. All this work is possible by changing the program (sequence of instructions for computers).
  • Diligence: Computer, being a machine, does not suffer from the human traits of tiredness and lack of concentration. If four million calculations have to be performed, then the computer will perform the last four-millionth calculation with the same accuracy and speed as the first calculation.
  • Resource Sharing: In the initial stages of development, computer used to be an isolated machine. With the tremendous growth in computer technologies, today’s computers have the capability to connect with each other. This has made the sharing of costly resources like printers possible. Apart from device sharing, data and information can also be shared among groups of computers, thus creating a large information and knowledge base.


Thinking: The computer cannot think itself. The concept of artificial intelligence shows that the computer can think. But still this concept is dependent on set of instructions provided by the human beings.


Self-Care: A Computer cannot care itself like a human. A computer is dependent still to human beings for this purpose.


Retrieval of memory: A computer can retrieve data very fast but this technique is linear. A human being’s mind does not follow this rule. A human mind can think randomly which a computer machine cannot.


Feelings: One of the main limits in the computer is of feeling. A computer cannot feel about some like a human. A computer cannot meet human in respect of relations.


Generations of Computer

While it would not be wrong to say that the evolution of the computer began with the man’s need to count, the actual growth of this field happened in a sort span of thirty years. This rapid development was characterized by phase of growth, which have come to be called computer generations. Major technological developments in each generation led to smaller, cheaper, more powerful and more efficient and reliable computers.

First Generation   – 1940-1956: Vacuum Tubes : First generation of computers started with using vacuum tubes as the basic components for memory and circuitry for CPU (Central Processing Unit). These tubes like electric bulbs produced a lot of heat and were prone to frequent fusing of the installations, therefore, were very expensive and could be afforded only by very large organizations.

In this generation, mainly batch processing operating systems were used. In this generation, Punched cards, Paper tape, Magnetic tape Input & Output device were used. There were machine codes and electric wired board languages used.

Characteristics of First-generation Computers

Following are the characteristics of first-generation computers:

The main features of First Generation are:

  • Vacuum tube technology
  • Unreliable
  • Supported Machine language only
  • Very costly
  • Generate a lot of heat
  • Slow Input/output device
  • Huge size
  • Need  A.C.
  • Non-portable
  • Consumed lot of electricity

Some computers of this generation were:

  • IBM-701
  • IBM-650

Second Generation 1956-1963: Transistors

Second-generation computers used transistors instead of vacuum tubes, which were superior to vacuum tubes. A transistor is made up of semiconductor material like germanium and silicon. It usually had three leads and performed electrical functions such as voltage, current or power amplification with low power requirements. Since transistor is a small device, the physical size of the computer was greatly reduced. Computers became smaller, faster, cheaper, energy-efficient and more reliable than their predecessors. In second-generation computers, magnetic cores were used as primary memory and magnetic disks as secondary storage devices. However, they still relied on punched cards for input and printouts for output.

One of the major developments of this generation includes the progress of machine language to assembly language. Assembly language used mnemonics (abbreviations) for instructions rather than numbers; for example, ADD for addition and MULT for multiplication. As a result, programming became less cumbersome. Early high-level programming languages such as COBOL and FORTRAN also came into existence during this period. Examples: PDP-8, IBM 1401 and IBM 7090.

Characteristics of Second-generation Computers

  • These machines were based on transistor technology.
  • These were smaller when compared to the first-generation computers.
  • The computational time of these computers was reduced to microseconds from milliseconds.
  • These were more reliable and less prone to hardware failure. Hence, they required less frequent maintenance.
  • These were more portable and generated less amount of heat.
  • Assembly language was used to program computers. Hence, programming became more time-efficient and less cumbersome.
  • Second-generation computers still required air conditioning.
  • Manual assembly of individual components into a functioning unit was still required.

Third-generation 1964-1971: Integrated Circuits: The development of the integrated circuit was the trait of the third-generation computers. An integrated circuit, also called IC, consisted of a single chip (usually silicon) with many components such as transistors and resistors fabricated on it Integrated circuits replaced several individually wired transistors.     This development made computers smaller in size, reliable and efficient. 

Instead of punched cards and printouts, users interacted with third-generation computers through keyboards and monitors and interfaced with an operating system. This allowed the device to run many different applications at one time with a central program that monitored the memory. For the first time, computers became accessible to majority of common people because they were smaller and cheaper than their predecessors.


Characteristics of Third generation computers

  • These computers were based on integrated circuit (IC) technology.
  • These were able to reduce computational time from microseconds to nanoseconds.
  • These were easily portable and more reliable than the second-generation computers.
  • These devices consumed less power and generated less heat. In some cases, air conditioning was still required.
  • The size of these computers was smaller as compared to previous-generation computers.
  • Since hardware rarely failed, the maintenance cost was quite low.
  • Extensive use of high-level languages became possible.
  • Manual assembling of individual components was not required; therefore, it reduced the large requirement of labor and cost. However, highly sophisticated technologies were required for the manufacturing of IC chips.
  • Commercial production became easier and cheaper.


Fourth generation (1971-1980): The fourth generation of computers is marked by the use of Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit elements and their associated circuits on a single chip made it possible to have microcomputers of fourth generation. Fourth Generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to personal computer (PC) revolution. In this generation, Timesharing, Real-time, Networks, Distributed Operating System were used. All the higher level languages like C and C++, DBASE, etc., were used in this generation.



Fifth Generation (1980-till date):  In the fifth generation, the VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components. This generation is based on parallel processing hardware and AI (Artificial Intelligence) software. AI is an emerging branch in computer science which interprets means and methods of making computers think like human beings. All the higher level languages like C and C++, Java, .Net, etc., are used in this generation.

AI includes:

  • Robotics
  • Neural networks
  • Game Playing
  • Development of expert systems to make decisions in real life situations.
  • Natural language understanding and generation.

The process of developing fifth-generation computers is still in the development stage. However, the ‘expert system’ concept is already in use. The expert system is defined as a computer system that attempts to mimic the thought process and reasoning of experts in specific

Three characteristics can be identified with the fifth-generation computers. These are as follows:

  • Mega Chips: Fifth-generation computers will use super large-scale integrated (SLSI) chips, which will result in the production of microprocessor having millions of electronic components on a single chip. To store instructions and information, fifth-generation computers require a great amount of storage capacity. Mega chips may enable the computer to approximate the memory capacity of the human mind.
  • Parallel Processing: Computers with one processor access and execute only one instruction at a time. This is called serial processing. However, fifth-generation computer will use multiple processors and perform parallel processing, thereby accessing several instructions at one time and working on them at the same time.
  • Artificial Intelligence (AI): It refers to a series of related technologies that tries to simulate and reproduce human behavior including thinking, speaking and reasoning. AI comprises a group of related technologies: expert systems (ES), natural language processing (NLP), speech recognition, vision recognition and robotics.