Generations and Classification of computer
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.
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| Vaccum Tube |
·
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.
Second Generation (1956 to
1963): Using Transistors
·
Hardware Technology Transistors (Figure 1.5) 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.
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| Transistors |
·
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.
Third Generation (1964 to 1971): Using Integrated Circuits
·
Hardware Technology The third generation computers used the Integrated Circuit (IC) chips. Figure 1.6 shows
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.
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| IC |
· 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.
1.5.2
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. A microprocessor chip is shown in Figure. 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.
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| Microprocessor |
·
Software Technology Several new operating systems like the MS-DOS and
MS- Windows 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.
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, and (4)
Supercomputer.
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| Classification of computer |
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.
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| Microcomputers |
·
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. Casio and Apple are some of the manufacturers of PDA. Over the last
few years, PDAs have merged 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 minicomputers.
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| Minicomputer |
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.
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| Mainframe computer |
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).
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| Supercomputer |
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