1.3 COMPUTER GENERATIONS
The evolution of computer started from 16th century and resulted in today‟s modern
machines. The present day computer, however, has also undergone rapid change over the
years. This period, during which the evolution of computer took place, can be divided
into five distinct phases known as Generations of Computers. Each new generation of
computers is not only superior from their predecessor in processing and capabilities but
also differs in looks and sizes. Each phase is distinguished from others on the basis of the
type of switching circuits used. These Generations are:
- First Generation Computers (1940-1956)
- Second Generation Computers (1956-1963)
- Fhird Generation Computers (1964-1971)
- Fourth Generation Computers (1971-Present)
- Fifth Generation Computers (Present and Beyond)
1.3.1- First Generation Computers: Vacuum Tubes (1940-1956)
First generation computers are characterized by the use of vacuum tube. A vacuum tube (First generation
computers are
characterized by
the use of
vacuum tube )was a fragile glass device, which used filaments as a source of electronics. It could
control and amplify electronic signals. These vacuum tubes were used for calculation as
well as storage and control. The first general purpose programmable electronic computer
was the Electronic Numerical Integrator and Computer (ENIAC), built by J. Presper
Eckert and John V. Mauchly at the University of Pennsylvania. The ENIAC was 30-50
feet long, weighed 30 tons, contained 18,000 vacuum tubes, 70,000 registers, 10,000
capacitors and required 150,000 watts of electricity. First generation computers were too
bulky in size which required large room for installation and they used to emit large
amount of heat, so air-condition was must for the proper working of computers. Programs
written in high level programming languages retranslated into assembly language or
machine language by a compiler. Assembly language program retranslated into machine
language by a program called an assembler (assembly language compiler).
Before ENIAC was finished, Von Neumann designed the Electronic Discrete Variable
Automatic Computer (EDVAC) with a memory to hold both a stored program as well as
data. This enabled much faster operation since the computer had rapid access to both data
and instructions. The other advantages of storing instruction were that computer could do
logical decision internally. Eckert and Mauchly later developed what was arguably the
first commercially successful computer, the Universal Automatic Computer (UNIVAC),
in 1952.
Examples: ENIAC, EDVAC, UNIVAC-1
1.3.2 - Second Generation Computers: Transistors (1956-1963)
Solid-State components (transistors and diodes) and magnetic core storage formed the
basis (Second
generation
computers are
characterized by
the use of
transistors )for the second generation of computers. Transistor is a device composed of
semiconductor material that amplifies a signal or opens or closes a circuit. Invented in
Bell Labs, transistors have become the key ingredient of all digital circuits, including
computers. Transistor replaced the bulky electric tubes in the first generation computer.
Transistors perform the same functions as a vacuum tube, except that electrons move
through solid materials instead of through a vacuum. Transistors were made of a semiconducting material and controlled the flow of electricity through the circuit. They also
allowed computers to become smaller and more powerful and faster at the same time.
They are also less expensive, required less electricity and emitted less heat than vacuum
tubes. Manufacturing cost was also very low.
It is in the second generation that the concept of Central Processing Unit (CPU), memory,
programming language and input and output units were developed. Second-generation
computers moved from cryptic binary machine language to symbolic, or assembly,
languages, which allowed programmers to specify instructions in words. These were also
the first computers that stored their instructions in their memory, which moved from a
magnetic drum to magnetic core technology. During the second generation many high
level programming languages were introduced, including FORTRAN (1956), ALGOL
(1958) and COBOL (1959).
Examples: PDP-8, IBM1400 series, IBM 1620, IBM 7090, CDC 3600
1.3.3- Third Generation Computers: Integrated Circuits (1964-1971)
The third generation computers were introduced in 1964. Transistors were miniaturized
and placed on silicon chips, called semiconductors, which drastically increased the speed
and efficiency of computers. They used Integrated Circuits (ICs). The development of (Third generation
computers are
characterized by the
use of integrated
circuits (ICs) ICs proved to be a milestone in the field of computer and electronics. These ICs are
popularly known as chips.
Silicon is the basic material used to make computer chips, transistors, silicon diodes and
other electronic circuits and switching devices because its atomic structure makes the
element an ideal semiconductor. Silicon is commonly doped, or mixed, with other
elements, such as boron, phosphorous and arsenic, to alter its conductive properties. A
typical chip is less than ¼-square inches and can contain millions of electronic
components (transistors). Computers consist of many chips placed on electronic boards
called printed circuit boards. There are different types of chips. For example, CPU chips
(also called microprocessors) contain an entire processing unit, whereas memory chips
contain blank memory.
A single IC, has many transistors, registers and capacitors built on a single thin slice of
silicon. Development in ICs ranges from small scale integration (SSI) to medium scale
integration (MSI). Multilayered printed circuits were developed and core memory was
replaced by faster, solid state memories. The IC technology was also known as
“microelectronics” technology, since large number of circuit could be integrated on a
single chip.
Computers of this generation were small in size, low cost, large memory and processing
speed is very high. Higher level language such as BASIC (Beginners All purpose
Symbolic Instruction Code) was developed during this period. Integrated solid-state
circuitry, improved secondary storage devices, and new input/output devices were the
most important advantages in this generation. The new circuitry increased the speed of
the computer. Arithmetic and logical operations were now being performed in
microseconds or even nanoseconds. The development of mini computers also took place
during this generation.
Examples: NCR 395, B6500, IBM 360,37
1.3.4- Fourth Generation Computers: Microprocessors (1971-Present)
Fourth generation computers started around 1971 by using large scale of integration (LSI)
in the construction of computing elements. LSI circuits built on a single silicon chip
called microprocessors. A microprocessor contains all the circuits required to perform
arithmetic, logic and control functions on a single chip. Because of microprocessors, the
fourth generation includes more data processing capacity than equivalent-sized third
generation computers. Due to the development of microprocessor it is possible to place
computer‟s central processing unit (CPU) on single chip. These computers are called
microcomputers. Later very large scale Integrated (VLSI) circuits replaced LSI circuits.
What in the first generation filled an entire room could now fit in the palm of the hand.
The Intel 4004chip, developed in 1971, located all the components of the computer -
from the central processing unit and memory to input/output controls - on a single chip. (Fourth
generation
computers are
characterized by
the use of
microprocessor )
The major innovations in this generation were the development of microelectronics and
the different areas in computer technology such as multiprocessing, multiprogramming,
time-sharing, operating speed, and virtual storage. During this period, high speed vector
processors changed the scenario of high performance computing. Mostly microcomputers and workstations were introduced for time shared mainframe computers. Thus the
computer which was occupying a very large room in earlier days can now be placed on a
table. The personal computer is a Fourth Generation Computer. It is the period when
evolution of computer networks also took place.
Examples: Apple II, Alter 8800
1.3.5 -Fifth Generation Computers (Present and Beyond)
Fifth generation computers, based on artificial intelligence, are still in development,
though there are some applications, such as voice recognition, that are being used today. (Fifth
generation
computers are
based on
Artificial
Intelligence ) Artificial Intelligence is the branch of computer science concerned with making
computers behave like humans and allow the computer to take its own decision.
Currently, no computers exhibit full artificial intelligence (that is, are able to simulate
human behavior). The greatest advances have occurred in the field of games playing. The
best computer chess programs are now capable of beating humans. Today, the hottest
area of artificial intelligence is neural networks, which are proving successful in an
umber of disciplines such as voice recognition and natural-language processing. There
are several programming languages that are known as AI languages because they are
used almost exclusively for AI applications. The two most common are LISP and Prolog.
The speed is extremely high in fifth generation computer. In the development of Fifth
generation computers, parallel processing attended the main focus of developers. Until
this time, parallelism was limited to pipelining and vector processing. This generation
introduced machines with hundreds of processors that could all be working on different
parts of a single program. Developments of more powerful computers are still in
progress. It has been predicted that such a computer will be able to communicate in
natural spoken language with its user, store vast knowledge databases, search rapidly
through these databases, making intelligent inferences, drawing logical conclusions,
image processing and see objects in the way that humans do.
Table 1.1 shows the comparative features of five generations of computers:
