First Generation 

1. The first generation of computers is said by some to have started in 1946 with ENIAC, the first 'computer' to use electronic valves (ie. vacuum tubes). Others would say it started in May 1949 with the introduction of EDSAC, the first stored program computer.

Advantages:

• That was the only electronic during those old days.
• Those computers were very fast to calculate.
• Vacuum tube technology made possible the advent of electronic digital computers.

Disadvantages:

• It is not really a reliable device.
• No portable
• It is required to be air conditioned.

Second Generation

The transition from first generation to second generation of computers was not abrupt. There was all round development in technology, designs and programming languages. Diode and transistor technology formed the basis of the electronic switches and the switching time came down to around 0.3 microseconds.

Advantages:

• Smaller in size compared to the first generation of computer
• The second generations computers were more reliable.
• Used less energy and were not heated as much as the first one.
• Wider commercial use.
• Better portability as compared to the first generation.
• Better speed and could calculate data in microseconds.
• Used faster peripherals.
• Used assembly language as well.
• Accuracy improved.

Disadvantages

• Cooling system was required.
• Constant maintenance was require.
• Costly and not versatile.
• Commercial production was difficult.
• Only used for specific purposes.
• Punch cards were used for input.

                             Third Generation

In this era, there were several innovations in various fields of computer technology. These include Integrated Circuits (ICs), Semiconductor Memories, Microprogramming, various patterns of parallel processing and introduction of Operating Systems and time-sharing. In the Integrated Circuit, division there was gradual progress. Firstly, there were small-scale integration (SSI) circuits (having 10 devices per chip), which evolved to medium scale integrated (MSI) circuits (having 100 devices per chip). There were also developments of multi-layered printed circuits.

Advantages:

• Less energy
• Easily portable
• Maintenance cost is low because hardware failures are rare.

Disadvantages:

• There are a lot of cases required for air conditioning.
• Highly sophisticated production was easier and cheaper.

                             Fourth Generation

After 1971 the fourth generation computers were built. The fourth generation computers were the extension of third generationtechnology. The fourth generation computers emerged withdevelopment of the VLSI (Very Large Scale Integration).With the help of VLSI technology microprocessor came into existence. The computers were designed by using microprocessor, as thousands ofintegrated circuits were built onto a single silicon chip. What in the first generation filled an entire room could now fit in the palm of the hand. The fourth generation computers became more powerful, compact, reliable and affordable. As a result, they give rise to personal computer (PC) revolution.
For the first time in 1981 IBM introduced its computer for the home user and in 1984 Apple introduced Macintosh Microprocessor.

Advantages:

• Air conditioning is not required in most cases.
• Faster in computation than the last generations
• Totally general purpose.
• Heat generated is negligible
• Smallest in size it's because of the high component density.

Disadvantages:

• Highly sophisticated technology required for the manufacture of LSI chips.

     

Fifth Generation

Fifth generation computers are in developmental stage which is based on theartificial intelligence. The goal of the fifth generation is to develop the device which could respond to natural language input and are capable of learning and self-organization. Quantum computation and molecular and nanotechnology will be used in this technology. So we can say that the fifth generation computers will have the power of human intelligence.

Advantages:

• It is more reliable and works faster.
• Available in different sizes with unique features.

Disadvantages:

• The disadvantages of fifth generation computers have yet to be agreed upon, but many feel that they are two of its advantages: AI and the overall advanced technology. The addition of AI worries many due to the computers possibly becoming smart enough to replace humans altogether, and many people are becoming reliant on the advanced technology for tasks that they can do without computers.