Each generation of computer 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 devices. The various
generations of computers an listed below :
(i) First Generation (1946-1954) : In 1946there was no 'best' way of
storing instructions and data in a computer memory. There were four competing
technologies for providing computer memory: electrostatic storage tubes,
acoustic delay lines (mercury or nickel), magnetic
drums (and disks?), and magnetic
core storage.
The digital computes using electronic valves (Vacuum
tubes) are known as first generation computers. the first 'computer' to use
electronic valves (ie. vacuum tubes). The high cost of vacuum tubes prevented
their use for main memory. They stored information in the form of
propagating sound waves.
Other Important Computers of First
Generation
Some other computers of this time worth mentioning are the
Whirlwind, developed at Massachussets Institute of Technology, and JOHNNIAC, by
the Rand Corporation. The Whirlwind was the first computer to display real time
video and use core memory. The JOHNNIAC was named in honor of Jon Von Neumann.
Computers at this time were usually kept in special locations like government
and university research labs or military compounds.
Limitations of First Generation Computer
Followings are the major drawbacks of First generation computers.
1. They used valves or vacuum tubes as their main electronic
component.
2. They were large in size, slow in processing and had less
storage capacity.
3. They consumed lots of electricity and produced lots of
heat.
4. Their computing capabilities were limited.
5. They were not so accurate and reliable.
6. They used machine level language for programming.
7. They were very expensive.
Example: ENIAC, UNIVAC, IBM 650 etc
(ii) Second Generation (1955-1964) : The
second-generation computer used transistors for CPU components
& ferrite cores for main memory & magnetic
disks for secondary memory. They used high-level languages
such as FORTRAN (1956), ALGOL (1960) & COBOL (1960 -
1961). I/O processor was included to control I/O operations.
Around 1955 a device called Transistor replaced
the bulky Vacuum tubes in the first generation computer. Transistors are
smaller than Vacuum tubes and have higher operating speed. They have no
filament and require no heating. Manufacturing cost was also very low. Thus the
size of the computer got reduced considerably.
It is in the second generation that the concept of Central
Processing Unit (CPU), memory, programming language and input and output units
were developed. The programming languages such as COBOL, FORTRAN were developed
during this period.
Features:
1. Transistors were used instead of Vacuum Tube.
2. Processing speed is faster than First Generation
Computers (Micro Second)
3. Smaller in Size (51 square feet)
4. The input and output devices were faster.
Example: IBM 1400 and 7000 Series, Control Data 3600 etc.
(iii) Third
Generation (1964-1977) : By the development of a small
chip consisting of the capacity of the 300 transistors.
These ICs are popularly known as Chips. A single IC has many transistors, registersand
capacitors built on a single thin slice of silicon. So
it is quite obvious that the size of the computer got further reduced. Some of
the computers developed during this period were IBM-360,
ICL-1900, IBM-370, and VAX-750. Higher level language such
as BASIC (Beginners All purpose Symbolic Instruction Code)was
developed during this period. Computers of this generation were small in
size, low cost, large memory and processing speed is very high. Very soon ICs
Were replaced by LSI (Large Scale Integration),
which consisted about 100 components. An IC containing about 100 components is
called LSI.
Features:
1. They used Integrated Circuit (IC) chips in place of the
transistors.
2. Semi conductor memory devices were used.
3. The size was greatly reduced, the speed of processing was
high, they were more accurate and reliable.
4. Large Scale Integration (LSI) and Very Large Scale
Integration (VLSI) were also developed.
5. The mini computers were introduced in this generation.
6. They used high level language for programming.
Example: IBM 360, IBM 370 etc.
(iv) Fourth Generation : An
IC containing about 100 components is called LSI (Large Scale Integration) and
the one, which has more than 1000 such components, is called as VLSI
(Very Large Scale Integration). It uses large
scale Integrated Circuits (LSIC) built on a single silicon
chip called microprocessors. 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 Circuits (VLSIC) replaced LSICs. Thus
the computer which was occupying a very large room in earlier days can now be
placed on a table. The personal computer (PC) that you see in your
school is a Fourth Generation Computer Main memory used fast semiconductors
chips up to 4 M bits size. Hard disks were used as secondary memory. Keyboards,
dot matrix printers etc. were developed. OS-such as MS-DOS,
UNIX, Apple’s Macintosh were available. Object oriented
language, C++ etc were developed.
Features:
1. They used Microprocessor (VLSI) as their main switching
element.
2. They are also called as micro computers or personal computers.
3. Their size varies from desktop to laptop or
palmtop.
4. They have very high speed of processing; they are 100%
accurate, reliable, diligent and versatile.
5. They have very large storage capacity.
Example: IBM PC, Apple-Macintosh etc.
(v) Fifth Generation (1991- continued) : 5th
generation computers use ULSI (Ultra-Large Scale Integration) chips. Millions
of transistors are placed in a single IC in ULSI chips. 64 bit microprocessors
have been developed during this period. Data flow & EPIC architecture of these
processors have been developed. RISC & CISC, both types of
designs are used in modern processors. Memory chips and flash memory up to 1
GB, hard disks up to 600 GB & optical disks up to 50 GB have been
developed. fifth generation digital computer will be Artificial
intelligence.