generation of computer and its clasification

GENERATIONS OF COMPUTER  

The computer has evolved from a large—sized simple calculating machine to a smaller but much
more powerful machine. The evolution of computer to the current state is defined in terms of the
generations of computer. Each generation of computer is designed based on a new technological
development, resulting in better, cheaper and smaller computers that are more powerful, faster
and efficient than their predecessors. Currently, there are five generations of computer. In the
following subsections, we will discuss the generations of computer in terms of—  

1. the technology used by them (hardware and software),
2. computing characteristics (speed, i.e., number of instructions executed per second),
3. physical appearance, and
4. their applications.  

First Generation (1940 to 1956): Using Vacuum Tubes  

• Hardware Technology The first generation of computers used vacuum tubes 

for circuitry and magnetic drums for memory. The input to the computer was through
punched cards and paper tapes. The output was displayed as printouts.

• Software Technology The instructions were written in machine language. Machine

language uses 0s and 1s for coding of the instructions. The first generation computers
could solve one problem at a time.

• Computing Characteristics The computation time was in milliseconds.
• Physical Appearance These computers were enormous in size and required a large room

for installation.

• Application They were used for scientific applications as they were the fastest computing

device of their time.

• Examples UNIVersal Automatic Computer (UNIVAC), Electronic Numerical Integrator

And Calculator (ENIAC), and Electronic Discrete Variable Automatic Computer
(EDVAC).
The first generation computers used a large number of vacuum tubes and thus generated a lot of
heat. They consumed a great deal of electricity and were expensive to operate. The machines
were prone to frequent malfunctioning and required constant maintenance. Since first generation
computers used machine language, they were difficult to program.  

vacuum tube

Second Generation (1956 to 1963): Using Transistors  

•  Hardware Technology Transistors replaced the vacuum tubes of the first

generation of computers. Transistors allowed computers to become smaller, faster,
cheaper, energy efficient and reliable. The second generation computers used magnetic
core technology for primary memory. They used magnetic tapes and magnetic disks for
secondary storage. The input was still through punched cards and the output using
printouts. They used the concept of a stored program, where instructions were stored in
the memory of computer.

• Software Technology The instructions were written using the assembly language.

Assembly language uses mnemonics like ADD for addition and SUB for subtraction for
coding of the instructions. It is easier to write instructions in assembly language, as
compared to writing instructions in machine language. High-level programming
languages, such as early versions of COBOL and FORTRAN were also developed during
this period.

• Computing Characteristics The computation time was in microseconds.
• Physical Appearance Transistors are smaller in size compared to vacuum tubes, thus, the

size of the computer was also reduced.

• Application The cost of commercial production of these computers was very high,

though less than the first generation computers. The transistors had to be assembled
manually in second generation computers.

• Examples PDP-8, IBM 1401 and CDC 1604.

Second generation computers generated a lot of heat but much less than the first generation
computers. They required less maintenance than the first generation computers.  

transistor

Third Generation (1964 to 1971): Using Integrated Circuits  

• Hardware Technology The third generation computers used the Integrated Circuit (IC)

chips.  In an IC chip, multiple transistors are placed on a
silicon chip. Silicon is a type of semiconductor. The use of IC chip increased the speed
and the efficiency of computer, manifold. The keyboard and monitor were used to
interact with the third generation computer, instead of the punched card and printouts.

• Software Technology The keyboard and the monitor were interfaced through the

operating system. Operating system allowed different applications to run at the same
time. High-level languages were used extensively for programming, instead of machine
language and assembly language.

• Computing Characteristics The computation time was in nanoseconds.
• Physical Appearance The size of these computers was quite small compared to the

second generation computers.

• Application Computers became accessible to mass audience. Computers were produced

commercially, and were smaller and cheaper than their predecessors.

• Examples IBM 370, PDP 11.

The third generation computers used less power and generated less heat than the second
generation computers. The cost of the computer reduced significantly, as individual components
of the computer were not required to be assembled manually. The maintenance cost of the
computers was also less compared to their predecessors  

IC( integrated circuit)

Fourth Generation (1971 to present): Using Microprocessors 

• Hardware Technology They use the Large Scale Integration (LSI) and the Very Large

Scale Integration (VLSI) technology. Thousands of transistors are integrated on a small
silicon chip using LSI technology. VLSI allows hundreds of thousands of components to
be integrated in a small chip. This era is marked by the development of microprocessor.Microprocessor is a chip containing millions of transistors and components, and,
designed using LSI and VLSI technology. 
This generation of computers gave rise to Personal Computer (PC). Semiconductor
memory replaced the earlier magnetic core memory, resulting in fast random access to
memory. Secondary storage device like magnetic disks became smaller in physical size
and larger in capacity. The linking of computers is another key development of this era.
The computers were linked to form networks that led to the emergence of the Internet.
This generation also saw the development of pointing devices like mouse, and handheld
devices.

• Software Technology Several new operating systems like the MS-DOS and MSWindows developed during this time. This generation of computers supported Graphical

User Interface (GUI). GUI is a user-friendly interface that allows user to interact with the
computer via menus and icons. High-level programming languages are used for the
writing of programs.

• Computing Characteristics The computation time is in picoseconds.
• Physical Appearance They are smaller than the computers of the previous generation.

Some can even fit into the palm of the hand.

• Application They became widely available for commercial purposes. Personal computers

became available to the home user.

• Examples The Intel 4004 chip was the first microprocessor. The components of the

computer like Central Processing Unit (CPU) and memory were located on a single chip.
In 1981, IBM introduced the first computer for home use. In 1984, Apple introduced the
Macintosh.
The microprocessor has resulted in the fourth generation computers being smaller and cheaper
than their predecessors. The fourth generation computers are also portable and more reliable.
They generate much lesser heat and require less maintenance compared to their predecessors.
GUI and pointing devices facilitate easy use and learning on the computer. Networking has
resulted in resource sharing and communication among different computers.

microprocessor

Fifth Generation (Present and Next): Using Artificial Intelligence  

The goal of fifth generation computing is to develop computers that are capable of learning and
self-organization. The fifth generation computers use Super Large Scale Integrated (SLSI) chips
that are able to store millions of components on a single chip. These computers have large
memory requirements.
This generation of computers uses parallel processing that allows several instructions to be
executed in parallel, instead of serial execution. Parallel processing results in faster processing
speed. The Intel dualcore microprocessor uses parallel processing.
The fifth generation computers are based on Artificial Intelligence (AI). They try to simulate the
human way of thinking and reasoning. Artificial Intelligence includes areas like Expert System
(ES), Natural Language Processing (NLP), speech recognition, voice recognition, robotics, etc  

CLASSIFICATION OF COMPUTER  

The digital computers that are available nowadays vary in their sizes and types. The computers
are broadly classified into four categories based on their size and type—

(1)Microcomputers

 (2) Minicomputers

(3) Mainframe computers

 (4) Supercomputer.

1. Microcomputers

Microcomputers are small, low-cost and single-user digital computer. They consist of CPU,
input unit, output unit, storage unit and the software. Although microcomputers are stand-alone
machines, they can be connected together to create a network of computers that can serve more
than one user. IBM PC based on Pentium microprocessor and Apple Macintosh are some
examples of microcomputers. Microcomputers include desktop computers, notebook computers
or laptop, tablet computer, handheld computer, smart phones and netbook.

LAPTOP

NETBOOK

PC

PDA

SMART PHONE

LAPTOP

•  Desktop Computer or Personal Computer (PC) is the most common type of

microcomputer. It is a stand-alone machine that can be placed on the desk. Externally, it
consists of three units—keyboard, monitor, and a system unit containing the CPU,
memory, hard disk drive, etc. It is not very expensive and is suited to the needs of a
single user at home, small business units, and organizations. Apple, Microsoft, HP, Dell
and Lenovo are some of the PC manufacturers.

•  Notebook Computers or Laptop resemble a notebook. They are portable and have all the

features of a desktop computer. The advantage of the laptop is that it is small in size (can
be put inside a briefcase), can be carried anywhere, has a battery backup and has all the
functionality of the desktop. Laptops can be placed on the lap while working (hence the
name). Laptops are costlier than the desktop machines.

• Netbook These are smaller notebooks optimized for low weight and low cost, and are

designed for accessing web-based applications. Starting with the earliest netbook in late
2007, they have gained significant popularity now. Netbooks deliver the performance
needed to enjoy popular activities like streaming videos or music, emailing, Web surfing
or instant messaging. The word netbook was created as a blend of Internet and notebook.

• Tablet Computer has features of the notebook computer but it can accept input from a

stylus or a pen instead of the keyboard or mouse. It is a portable computer. Tablet
computer are the new kind of PCs.

•  Handheld Computer or Personal Digital Assistant (PDA) is a small computer that can be held on the top of the palm. It is small in size. Instead of the keyboard, PDA uses a pen or a stylus for input. PDAs do not have a disk drive. They have a limited memory and are less powerful. PDAs can be connected to the Internet via a wireless connection. Casioand Apple are some of the manufacturers of PDA. Over the last few years, PDAs havemerged into mobile phones to create smart phones.
• Smart Phones are cellular phones that function both as a phone and as a small PC. They

may use a stylus or a pen, or may have a small keyboard. They can be connected to the
Internet wirelessly. They are used to access the electronic-mail, download music, play
games, etc. Blackberry, Apple, HTC, Nokia and LG are some of the manufacturers of
smart phones.

Minicomputers

Minicomputers are digital computers, generally used in multi-user systems. They
have high processing speed and high storage capacity than the microcomputers. Minicomputers
can support 4–200 users simultaneously. The users can access the minicomputer through their
PCs or terminal. They are used for real-time applications in industries, research centers, etc. PDP
11, IBM (8000 series) are some of the widely used minicomputer.  

mini computer

Mainframe Computers

Mainframe computers are multi-user, multi-programming and high performance
computers. They operate at a very high speed, have very large storage capacity and can handle
the workload of many users. Mainframe computers are large and powerful systems generally
used in centralized databases. The user accesses the mainframe computer via a terminal that may
be a dumb terminal, an intelligent terminal or a PC. A dumb terminal cannot store data or do
processing of its own. It has the input and output device only. An intelligent terminal has the
input and output device, can do processing, but, cannot store data of its own. The dumb and the
intelligent terminal use the processing power and the storage facility of the mainframe computer.
Mainframe computers are used in organizations like banks or companies, where many people
require frequent access to the same data. Some examples of mainframes are CDC 6600 and IBM
ES000 series.  

Supercomputers

Supercomputers are the fastest and the most expensive machines. They have high
processing speed compared to other computers. The speed of a supercomputer is generally
measured in FLOPS (FLoating point Operations Per Second). Some of the faster supercomputers
can perform trillions of calculations per second. Supercomputers are built by interconnecting
thousands of processors that can work in parallel.
Supercomputers are used for highly calculation-intensive tasks, such as, weather forecasting,
climate research (global warming), molecular research, biological research, nuclear research and
aircraft design. They are also used in major universities, military agencies and scientific research
laboratories. Some examples of supercomputers are IBM Roadrunner, IBM Blue gene and Intel
ASCI red. PARAM is a series of supercomputer assembled in India by C-DAC (Center for
Development of Advanced Computing), in Pune. PARAM Padma is the latest machine in this
series. The peak computing power of PARAM Padma is 1 Tera FLOP (TFLOP).

super computer