The document summarizes the five generations of computers based on their technological developments. The first generation used vacuum tubes, the second used transistors, the third used integrated circuits, the fourth used microprocessors, and the fifth generation focuses on artificial intelligence. Each generation brought improvements in size, cost, speed, reliability and other factors. The document also categorizes computers based on their principles of operation and configuration.

1. Generations of Computer
The development of computers has followed difference steps in the
technology used and these steps of technological differences are called
as generations.
Each of the five generations of computers is characterized by a major
technological development that fundamentally changed the way
computers operate, resulting in increasingly smaller, cheaper, more
powerful and more efficient and reliable computing devices.
First Generation (1945-1960) Vacuum Tubes :
The first generation of computers used vacuum tubes for circuitry and
magnetic drums. Vacuum tube is a fragile glass device that can control
and amplify electronic signals. They are using 18,000 vacuum tubes,
70,000 resisters, 10,000 capacitors and 60,000 switches. First
generation computers relied on machine language, the lowest-level
programming language understood by computers, to perform
operations.

2. Disadvantages:
• It took 150 kilo watt electric power and it produce large
amount of heat, which was often the cause of malfunctions.
• They were bulky and required large space.
• They had small primitive memories and no auxiliary storage.
• They were very expensive to operate .
• They could only solve one problem at a time.
• Input was based on punched cards and paper tape, and
output was displayed on printouts.
Example:
• ENIAC, EDVAC, EDSAC,UNIVAC etc.
• UNIVAC was the first commercial computer delivered to a
business client, the U.S. Census Bureau in 1951.

3. Second Generation (1956-1963) Transistors
With the development of transistors and their use in circuits,
magnetic core for memory storage, the vacuum tubes of first
generation are replaced by transistors to arrive at second generation
of computers.
Advantages over 1st generation:
• The size of transistors is much smaller when compared to
vacuum tubes.
• They consumed less power generated less heat .
• They are faster and reliable.
• The major advantage use of transistors was that the size of
computer has come down .
• The power consumption also less.
• Even the cost of transistors is less in comparison with the cost of
vacuum tubes.
• In this generation , magnetic tapes were used for storing.

4. Disadvantages:
• still generated a great deal of heat that subjected the computer to
damage,
• still relied on punched cards for input and printouts for output.
Second-generation computers moved from cryptic binary machine
language to symbolic, or assembly, languages, which allowed
programmers to specify instructions in words. High-level
programming languages were also being developed at this time, such
as early versions of Cobol and Fortran, Snowbal, Algol etc.
The first computers of this generation were developed for the atomic
energy industry.

5. Third Generation (1964-1971) Integrated Circuits
The third generation of computers used compact integrated circuits
(IC's) of silicon chips in place of transistors. Each of these IC's
consisted of large number of chips in very small packages. Transistors
were miniaturized and placed on silicon chips, called semiconductors.
These machines used IC's with LSI (Large Scale Integration).
Advantages:
• Drastically increased the speed and efficiency of computers.
• Instead of punched cards and printouts, keyboards and monitors were
introduced and interfaced with an operating system.
• the device to run many different applications at one time with a
central program that monitored the memory.
• first time became accessible to a mass audience because they were
smaller and cheaper than their predecessors.
• the size of computers, cost, heat generation and power consumption
decreased to a great extent, speed and reliability increased as
compared to previous generations.

6. Fourth Generation (1971-Present) Microprocessors
The microprocessor brought the fourth generation of computers.
These generation used Integrated Circuits with VLSI (Very Large
Scale Integration). Thousands of integrated circuits were built onto a
single silicon chip.
Advantages:
• These computers have high processing powers.
• Low maintenance.
• High reliability .
• Very low power consumption.
• These computer reduces the cost as well as the size of the computer.
First generation filled an entire room could now fit in the palm of
the hand.
• Small computers became more powerful, they could be linked
together to form networks, which eventually led to the development
of the Internet.

7. In 1971, the Intel 4004 chip was developed, located all the
components of the computer—from the central processing unit and
memory to input/output controls—on a single chip.
In 1981 IBM, introduced its first computer for the home user, and
in 1984 Apple introduced the Macintosh.
Fourth generation computers also saw the development of GUIs,
the mouse and handheld devices.

8. Fifth Generation (Present and Beyond) Artificial Intelligence
Fifth generation computers use optic fiber technology to handle
Artificial Intelligence, expert systems, robotics etc., are still in
development, though there are some applications, such as voice
recognition, that are being used today. The use of parallel processing
and superconductors is helping to make artificial intelligence a reality.
Quantum computation, molecular and nanotechnology will radically
change the face of computers in years to come.
Advantages:
• Very high processing speeds .
• More reliable.
Goal:
The goal of fifth-generation computing is to develop devices that
respond to natural language input and are capable of learning and
self-organization.

10. TYPES OF COMPUTERS
Computers can be classified based on their principles of operation or on
their configuration. By configuration, i.e, the size, speed of doing
computation and storage capacity of a computer.
• Types of Computers based on Principles of Operation
There are three different types of computers according to the principles
of operation. Those are-
• Analog Computers
• Digital Computers
• Hybrid Computers

11. Analog Computers
Analog Computer is a computing device that works on continuous
range of values. The results given by the analog computers will only be
approximate since they deal with quantities that vary continuously.
Uses:
It generally deals with physical variables such as voltage, pressure,
temperature, speed, etc.
Digital Computers
It 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. It 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.
Uses:
• 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.

12. Based on the purpose, Digital computers can be further classified as,
• General Purpose Computers
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.
• Special Purpose Computers
Special purpose computer is one that is built for a specific
application.
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.

13. 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.
Types of Computers based on Configuration
There are four different types of computers when we classify them based
on their performance and capacity. The four types are
• Super Computers
• Mainframe Computers
• Mini Computers
• Micro Computers

14. Super Computers
They are the best in terms of processing capacity and also the most
expensive ones. These computers can process billions of instructions per
second.
Uses:
• Used for applications, require intensive numerical computations such
as stock analysis, weather forecasting etc.
• Other uses of supercomputers are scientific simulations, graphics,
fluid dynamic calculations, nuclear energy research, electronic design,
and analysis of geological data .
Companies which produce super computers are Cray, IBM and Hewlett-
Packard.
Mainframe Computers
It can also process data at very high speeds i.e., hundreds of million
instructions per second and they are also quite expensive.
Uses:
• Normally, they are used in banking, airlines and railways etc for their
applications.

15. Mini Computers
Mini computers are lower to mainframe computers in terms of speed and
storage capacity. They are also less expensive than mainframe
computers. Some of the features of mainframes will not be available in
mini computers. Hence, their performance also will be less than that of
mainframes.
Micro Computers
The invention of microprocessor (single chip CPU) helped to produce
the much cheaper micro computers. They are further classified into
• Desktop Computers: These desktop computers are also known as
personal computers or simply PCs. They are
usually easier to use and more affordable and
normally intended for individual users for their
word processing and other small application
requirements.

16. • Laptop Computers : Laptop computers are portable computers.
They are lightweight computers with a thin
screen. They are also called as notebook
computers because of their small size. They
can operate on batteries and hence are very
popular with travelers.
•Handheld Computers(PDAs): Handheld computers or Personal
Digital Assistants (PDAs) are pen-
based and also battery-powered.
They are small and can be carried anywhere. They use a pen like
stylus and accept handwritten input directly on the screen. They are not
as powerful as desktops or laptops but they are used for scheduling
appointments, storing addresses and playing games. They have touch
screens which we use with a finger or a stylus.