The first
electronic computer was designed and built at the University of Pennsylvania
based on vacuum tube technology. Vacuum tubes were used to perform logic
operations and to store data. Generations of computers has been divided into
five according to the development of technologies used to fabricate the
processors, memories and I/O units.
I Generation:
1945 – 55
II Generation:
1955 – 65
III Generation:
1965 – 75
IV Generation:
1975 – 89
V Generation:
1989 to present
First Generation
ENIAC - Electronic
Numerical Integrator And Calculator, 1946
EDSAC – Electronic
Delay Storage Automatic Calculator, 1949
EDVAC – Electronic
Discrete Variable Automatic Computer, 1949
UNIVAC – Universal
Automatic Computer, 1951
·
The first large electronic computer was
completed in 1946 by a team led by Eckert &Mauchly at the university of
Pennsylvania in USA, this computer called as ENIAC
·
Vacuum tubes were used
·
ENIAC took about 200 microseconds to add two
digits & about 2800 microseconds to multiply.
·
EDSAC was completed in 1949 & used mercury
delay lines for storage.
·
Storage
Device: Acoustic delay lines and later magnetic drum. Memory capacity of 1 Kb
memory.
·
Switching
Time: 0.1 to 1 mili sec
·
MTBF
(Mean time between Failure): 30 min to 1 hr.
·
It stores machine instructions in the memory of
the computer along with data
·
Designed at Cambridge University UK, under
leadership of Prof. Maurice Wilkes.
·
UNIVAC I built by Univac division of Remington
Rand & delivered in 1951.
Details of First Generation
·
Bulky
·
Consume more power with limited performance
·
High cost
·
Uses assembly language – to prepare programs.
These were translated into machine level language for execution.
·
Mercury delay line memories and Electrostatic
memories were used
·
Fixed point arithmetic was used
·
Punched cards and paper tape were invented to
feed programs and data and to get results.
·
Magnetic tape / magnetic drum were used as
secondary memory
·
Mainly used for scientific computations.
Second
Generation (Manufacturers – IBM 7030, Digital Data Corporation’s PDP 1/5/8
Honeywell 400)
·
Transistors were used in place of vacuum tubes.
(Inventedat AT&T Bell lab in 1947. By, Bardeen, Brattain & Shockley in
1947.)
·
Small in size
·
Lesser power consumption and better performance
·
Lower cost
·
Switching
Time: 1 to 10 micro sec
·
MTBF
(Mean time between Failure): about 10 hrs.
·
Memory capacity of 100 KB
·
Magnetic ferrite core memories were used as main
memory which is a random-access nonvolatile memory
·
Magnetic tapes and magnetic disks were used as
secondary memory
·
Hardware for floating point arithmetic
operations was developed.
·
Index registers were introduced which increased
flexibility of programming.
·
High level languages such as FORTRAN, COBOL
(Common Business Oriented Language)etc were used - Compilers were developed to
translate the high-level program into corresponding assembly language program
which was then translated into machine language.
·
Separate input-output processors were developed
that could operate in parallel with CPU.
·
Punched cards continued during this period also.
·
Increasingly used in business, industry and
commercial organizations for preparation of payroll, inventory control,
marketing, production planning, research, scientific & engineering analysis
and design etc.
Third Generation (System 360
Mainframe from IBM, PDP-8 Mini Computer from Digital Equipment Corporation)
·
In 1965 with germanium transistors being
replaced by Silicon transistors
·
ICs were used, IC’s are consist of transistors,
resistors & capacitors on a single chip
·
Small Scale Integration (10 transistors per
chip) and Medium Scale Integration (100 transistors per chip) technology were
implemented in CPU, I/O processors etc.
·
Storage
Device: High speed magnetic cores. 100 Mb memory. 1 Mb main memory (hard disk)
·
Switching
Time: 0.1 to 1 micro sec
·
MTBF
(Mean time between Failure): 100 hrs.
·
Smaller & better performance
·
Comparatively lesser cost
·
Faster processors
·
In the beginning magnetic core memories were
used. Later they were replaced by semiconductor memories (RAM & ROM)
·
Introduced microprogramming
·
Microprogramming, parallel processing
(pipelining, multiprocessor system etc), multiprogramming, multi-user system
(time shared system) etc were introduced.
·
Operating system software were introduced
(efficient sharing of a computer system by several user programs)
·
Cache and virtual memories were introduced
(Cache memory makes the main memory appear faster than it really is. Virtual
memory makes it appear larger)
·
High level languages were improved &
standardized by ANSI (American National Standards Institute)eg. FORTRAN IV, COBOL
68etc
·
Database management, multi-user application,
online systems like closed loop process control, airline reservation,
interactive query systems, automatic industrial control etc emerged during this
period.
Fourth Generation (Intel’s
8088,80286,80386,80486 .., Motorola’s 68000, 68030, 68040, Apple II, CRAY
I/2/X/MP etc)
·
Microprocessors were introduced as CPU– Complete
processors and large section of main memory could be implemented in a single
chip
·
Tens of thousands of transistors can be placed
in a single chip (VLSI design implemented)
·
Storage
Device: Semiconductor memory. 10 Mb-512 Mb main memory. Hard disk 2-16gb
·
Switching
Time: 10 to 100 nano sec
·
MTBF
(Mean time between Failure): 1000 hrs.
·
CRT screen, laser & ink jet printers,
scanners etc were developed.
·
Semiconductor memory chips were used as the main
memory.
·
Secondary memory was composed of hard disks –
Floppy disks & magnetic tapes were used for backup memory
·
Parallelism, pipelining cache memory and virtual
memory were applied in a better way
·
LAN and WANS were developed (where desktop work
stations interconnected)
·
Introduced C language and Unix OS
·
Introduced Graphical User Interface
·
Less power consumption
·
High performance, lower cost and very compact
·
Much increase in the speed of operation
Fifth Generation (IBM notebooks,
Pentium PCs-Pentium 1/2/3/4/Dual core/Quad core. SUN work stations, Origin
2000, PARAM 10000, IBM SP/2)
·
Generation number beyond IV, have been used
occasionally to describe some current computer system that have a dominant
organizational or application driven feature.
·
Storage
Device: Semiconductor memory. 1 Gb-4 Gb main memory. Hard disk is 40 Gb-1 Tb
·
Switching
Time: 1 to 10 nano sec
·
MTBF
(Mean time between Failure): 10000 hrs.
·
Computers based on artificial intelligence are
available
·
Computers use extensive parallel processing,
multiple pipelines, multiple processors etc.
·
Massive parallel machines and extensively
distributed system connected by communication networks fall in this category.
·
Introduced ULSI (Ultra Large Scale Integration)
technology – Intel’s Pentium 4 microprocessor contains 55 million transistors
millions of components on a single IC chip.
·
Superscalar processors, Vector processors, SIMD
processors, 32 bit micro controllers and embedded processors, Digital Signal
Processors (DSP) etc have been developed.
·
Memory chips up to 1 GB, hard disk drives up to
180 GB and optical disks up to 27 GB are available (still the capacity is
increasing)
·
Object oriented language like JAVA suitable for
internet programming has been developed.
·
Portable note book computers introduced
·
Storage technology advanced – large main memory
and disk storage available
·
Introduced World Wide Web. (and other existing
applications like e-mail, e Commerce, Virtual libraries/Classrooms, multimedia
applications etc.)
·
New operating systems developed – Windows
95/98/XP/…, LINUX, etc.
·
Got hot pluggable features – which enable a
failed component to be replaced with a new one without the need to shutdown the
system, allowing the uptime of the system to be very high.
·
The recent development in the application of
internet is the Grid technology which is still in its upcoming stage.
·
Quantum mechanism and nanotechnology will
radically change the phase of computers.
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