Thursday, October 16, 2014


            "Generation" in computer talk is a step in technology. It provides a framework for the growth of the computer industry. The custom of referring to the computer era in terms of generations came into wide use only after 1964. There are totally five computer generations known till today. Although there is a certain amount of overlapping between the generations, the approximate dates shown against each are normally accepted.
FIRST GENERATION (1942 - 1955)
We have already discussed about some of the early computer - ENIAC, EDVAC, EDSAC, etc. These machines and other of their time were made possible by the invention of "vacuum tube", which could control and amplify electronic signals. These vacuum tube computers are referred to as first-generation computers.
1.      Vacuum tubes were the only electronic components available during those days.
2.      Vacuum tube technology made possible the advent of electronic digital computers.
3.      These computers were the fastest calculating devices of their time. They could perform computations in milliseconds.
1.      Too bulky in size.
2.      Unreliable.
3.               Thousands of vacuum tubes that were used emitted large amount of heat and burnt out frequently
4.      Air conditioning required.
5.      Prone to frequent hardware failures.
6.      Constant maintenance required.
7.      No portable.
8.      Manual assembly of individual components into functioning unit required.
9.      Commercial production was difficult and costly.
10.  Limited commercial use.
The transistor, a smaller and more reliable successor to the vacuum tube, was invented in 1947. However, computers that used were not produced in quantity until over a decade later. The second generation emerged with transistors being the brain of the computer.
With both the first and the second-generation computers, the basic component was a discrete or separate entity. The manual assembly of individual components and the cost of labor involved at this assembly stage made the commercial production of these computers difficult and costly.

1.      Smaller in size as compared to first generation computers.
2.            More reliable.
3.            Less heat generated.
4.                  These computers were able to reduce computational times from milliseconds to microseconds.
5.            Less prone to hardware failures.
6.            Better portability.
7.            Wider commercial use.
1.      Air-conditioning required.
2.      Frequent maintenance required.
3.      Manual assembly of individual components into a functioning unit was required.
4.      Commercial production was difficult and costly.
THIRD GENERATION (1964 - 1975)
Advances in electronics technology continued and the advent of "microelectronics" technology made it possible to integrate large number of circuit elements into very small (less than 5 mm square) surface of silicon known as "chips". This new technology was called "integrated circuits" (ICs). The third generation was based on IC technology and the computers that were designed with the use of integrated circuits were called third generation computers.
1.            Smaller in size as compared to previous generation computers.
2.            Even more reliable than second-generation computers.
3.            Even lower heat generated than second generation computers.
4.                  These computers were able to reduce computational times from microseconds to nano seconds.
5.            Maintenance cost is low because hardware failures are rare.
6.            Easily portable.
7.                  Totally general purpose. Widely used for various commercial applications all over the world.
8.            Less power requirement than previous generation computers.
9.            Commercial production was easier and cheaper.
1.      Air-conditioning required in many cases.
2.      Highly sophisticated technology required for the manufacture of IC chips.
Initially, the integrated circuits contained only about ten to twenty components. This technology was named small scale integration (SSI). Latter, with the advancement in technology for manufacturing ICs, it became possible to integrate upto a hundred components on a single chip. This technology came to be known as medium scale integration (MSI). Then came the era of large scale integration (LSI) when it was possible to integrate over 30,000 components onto a single chip. Effort is still on for further miniaturization and it is expected that more than one million components will be integrated on a single chip known as very large scale integration (VLSI).
A fourth generation computer, which is what we have now, has LSI chips as its brain. It is LSI technology, which has led to the development of very small but extremely powerful computers. on. A whole computer circuit was soon available on a single ship. They became inexpensive to make and suddenly it became possible for anyone and everyone to own a computer.
1.      Smallest in size because of high component density.
2.      Very reliable.
3.      Heat generated is negligible.
4.      No air conditioning required in most cases.
5.      Much faster in computation than previous generations.
6.      Hardware failure is negligible and hence minimal maintenance is required.
7.      Easily portable because of their small size.
8.      Totally general purpose.
1.      Highly sophisticated technology required for the manufacture of LSI chips.
Scientists are now at work on the fifth generation computers - a promise, but not yet a reality. They aim to bring us machines with genuine I.Q., the ability to reason logically, and with real knowledge of the world. Thus, unlike the last four generations that naturally followed its predecessor, the fifth generation will be totally different and totally new.
In structure it will be parallel (the present ones are serial) and will be able to do multiple tasks simultaneously. In functions, it will not be algorithmic (step by step, with one step at a time). In nature, it will not do just data processing (number crunching) but knowledge processing.  In programming, it will interact with humans in ordinary language (unlike BASIC, COBOL, FORTRAN, etc. which present computers need). And in architecture, it will have KIPS (Knowledge Information Processing System) rather than the present DIPS/LIPS (Data/Logic Information Processing System).
The odds of coming out with a fifth generation computer are heaviest for Japan. They have already started work in this direction few years back. Japan has chosen the PROLOG (Programming in Logic) language as its operating software and plans to have the final machine talk with human beings, see and deliver pictures and hear the normal, natural language.

Analog computer

The term analog does not relate to how the computer is powered and it is possible to have electronic analog computers. The characteristics of an analog computer mean it can be better than a digital computer at particular tasks.
A computer is simply a machine which processes data in a set fashion or, to put it another way, calculates. Today most computers are digital and work by reducing all data to binary numbers before processing. Analog computers go back thousands of years but vary from digital computers in only two fundamental ways.
The first is that an analog computer works in parallel. This means it can carry out multiple tasks simultaneously. A digital computer, even though it may work considerably faster, can only perform one calculation at any one instant. The only way around this in a digital computer is parallel computing, where a single machine has multiple processors. Even then, programs must often be rewritten to take advantage of this.
The second difference is that an analog computer handles continuous variables, while a digital computer works with discrete numbers. The difference between these is that continuous variables can include every conceivable number, even irrational numbers.

Digital Computers

On the other hand 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.
The digital computer is designed using digital circuits in which there are two levels for an input or output signal. These two levels are known as logic 0 and logic 1. Digital Computers can give more accurate and faster results.
Digital computer is well suited for solving complex problems in engineering and technology. Hence digital computers have an increasing use in the field of design, research and data processing.
Based on the purpose, Digital computers can be further classified as,
  • General Purpose Computers
  • Special Purpose Computers
Special purpose computer is one that is built for a specific application. General purpose computers are used for any type of applications. They can store different programs and do the jobs as per the instructions specified on those programs. Most of the computers that we see today are general purpose computers.

Hybrid Computers

A hybrid computer combines the desirable features of analog and digital computers. It is mostly used for automatic operations of complicated physical processes and machines. Now-a-days analog-to-digital and digital-to-analog converters are used for transforming the data into suitable form for either type of computation.
For example, in hospital’s ICU, analog devices might measure the patients temperature, blood pressure and other vital signs. These measurements which are in analog might then be converted into numbers and supplied to digital components in the system. These components are used to monitor the patient’s vital sign and send signals if any abnormal readings are detected. Hybrid computers are mainly used for specialized tasks.


Mini Computer

These are powerful computer. These computers come into existence in 1960s at that time mainframe computer was very costly. Mini computers were available in cheap prices, so users start using it. A midsized computer. In size and power, minicomputers lie between workstations and mainframes. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the distinction between small minicomputers and workstations. But in general, a minicomputer is a multiprocessing system capable of supporting from 4 to about 200 users simultaneously.

Micro computers:

These computers use a microprocessor chip and this chip is used instead of CPU means that this microprocessor chip works as a CPU. These computers are also called personal computers. Two major types of these computers are laptop or Desktop computers. Only one user uses these computers at time that's why they are also known as personal computers.

Mainframe Computer

It was a very powerful and large computer. You can get idea of its power as it can handle processing of many users at a time.  Terminals are used to connect a user to this computer and users submit their task through mainframe. Terminal is a device which has keyboard and a screen. By using terminal users put inputs into the computer and get the output through screen. A very large and expensive computer capable of supporting hundreds, or even thousands, of users simultaneously. In some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program faster than a mainframe.

Super Computer

The name "super computer" specifies that these are most powerful computers even than mainframe. Actually, when we optimize a mainframe computer then we get super computer.
The fastest and most powerful type of computer Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.
The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently.

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