GENERATIONS OF COMPUTERS

  The history of computer development is often discussed with reference to different

generations of computing devices. In computer terminology, the word generation is described as
a stage of technological development or innovation. A major technological development that
fundamentally changed the way computers operate resulting in increasingly smaller, cheaper,
more powerful and more efficient and reliable devices characterize each generation of
computers.

1. First Generation (1940-1956):Vacuum Tubes

First generation computers were vacuum tube / thermionic valves-based machines. These
computers used vacuum tubes for circuitry and magnetic drums for memory. A magnetic drum
is a metal cylinder coated with magnetic iron-oxide material on which data and programs can be
stored. Input was based on punched cards and paper tape, and output was displayed on printouts.
First generation computers relied on binary-coded language (language of 0s and 1s) to
perform operations and were able to solve only one problem at a time. Each machine was fed
with different binary codes and hence were difficult to program. This resulted in lack of
versatility and speed. In addition, to run on different types of computers, instructions must be
rewritten or recompiled.

 Examples: ENIAC, EDVAC, and UNIVAC.

Characteristics of first generations computers:

• These computers were based on vacuum tube technology.
• These were the fastest computing devices of their times. (computation time was in milliseconds)
• These computers were very large, and required a lot of space for installation.
• Since thousands of vacuum tubes were used, they generated a large amount of heat. Therefore, air conditioning was essential.
• These were non-portable and very slow equipments.
•  The lacked in versatility and speed.
• They were very expensive to operate and used a large amount of electricity.
• These machines were unreliable and prone to frequent hardware failures. Hence, constantmaintenance was required.
• Since machine language was used, these computers were difficult to program and use.
• Each individual component had to be assembled manually. Hence, commercial appeal of these computers was poor.

2. Second Generation Computers (1956-1963):Transistors

In the sixties, there was lot of development in semiconductor field - a field of materials. In
vacuum tubes, a filament is heated to emit electrons,(the basic component of an atom)that carry
current. In 1946,Willam Shockley and a few of his colleagues invented transistors, which do not
need any heating to liberate electrons in addition to being smaller in size, they saved power due
to the absence of heating and hence the cooling needed. the smaller size resulted in smaller
distances that the electrons have to travel to transmit information from one part of the computer
to another. Hence calculations became faster. The reliability also increased. Today you cannot
see any second generation computers.
The smaller size of components saw mass production of computers which became
cheaper. Many companies started buying and using them increasing the demand. Computer
programming languages developed further to make programming easier and user friendly. yet if
you compare today’s computers, they were a lot behind. The increased use of computers and the
consequent mass production sent the prices crashing down. Computer scientists and electronic
engineers were developing more sophisticated computers.

Characteristics of second generation computers:

• These machines were based on transistor technology.
• These were smaller as compared to the first generation computers.
• The computational time of these computers was reduced to microseconds form milliseconds.
• These were more reliable and less prone to hardware failure. Hence, such computer required less frequent maintenance.
• These were more portable and generated less amount of heat.
• Assemble 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.

 3. Third Generation Computers(1964 - early 1970s):Integrated circuits

In second generation computers, one could recognize the circuit components such as
transistors, resistors and capacitors distinctly. There were physically separate or “discreet”.
Slowly scientists started integrating these components together so that they are not separate.
They were fused into the circuits. People called it large scale integrated circuits (LSI).
Computers using such components were called third generation computers. Since components
were packed together more densely, the size of computers became smaller. Programmers also
developed more sophisticated software. By 1970, engineers developed a device called
microprocessor. Lot of circuits was packed into it. Intel 4004 was one such chip.

Characteristics of third generations computers:

• These computers were based on integrated circuit (IC) technology.
• They were able to reduce computational time from microseconds to nanoseconds.
• They were easily portable and more reliable than the second generation.
• 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 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, so it reduced the large requirement of labour and cost. However, highly sophisticated technologies were required for the manufacture of IC chips.
• Commercial production became easier and cheaper.

4. Fourth Generation Computers (Early 1970s – till date):Micro processors

More and more circuits were packed in a microprocessor. The components were
integrated further and very large scale integration (VLSI) technology revolutionized computer
field further. Intel Corporation made chips such as 8080 and 8086 to be followed by 80286,
80386, 80486 and now the Pentium processor. These chips perform calculations faster. They are
not only used in computers, but also in measuring devices and even in house hold devices such
as washing machines.
Computers using such VLSI chips progressively shrunk in size. Computers using the
microprocessors are termed as microcomputers. The software technology also developed further.
Programmers developed more sophisticated and user friendly software. In course of time, the
cost of these computers have come down so much that even individuals bought them so they
came to be known as personal computers.

Characteristics of Fourth generation computers:

• Fourth generation computers are microprocessor-based systems.
• These computers are very small.
• Fourth generation computers are the cheapest among all the other generations.
• They are portable and quite reliable.
• These machines generate negligible amount of heat, hence they do not require air conditioning. 
• Hardware failure is negligible so minimum maintenance is required. The production cost is very low.
• GUI and pointing devices enable users to learn to use the computer quickly.
• Interconnection of computers leads to better communication and resource sharing.

5. Fifth Generation Computers (Present and beyond):Artificial Intelligence

Up to fourth generation, the classification was based purely on hardware. Fifth generation
computers are classified based on software also. VLSI technology is used in fifth generation
computers. They have large main memories. The speed is also high. In addition to all this, Fifth
generation computers run software called ‘expert systems’.

Characteristics of Fifth Generation computers:

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. In order 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:
Most computers today access and execute only one instruction at a time. This is called
serial processing. However, a computer using parallel processing accesses several instructions at
once and works on them at the same time through use of multiple central processing units.

Artificial Intelligence (AI):
It refers to a series of related technologies that tries to simulate and reproduce human
behaviour, 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.