You know that the evolution of computer started from 16th century and resulted in the form that we see today. The present day computer, however, has also undergone rapid changes during the last fifty years. This period, during which the evolution of computer took place, can be divided into five distinct phases known as Generations of Computers. Generation of computer means the technological evolution over the period of time. Computers are classified as belonging to specific “generations”. The term generations was initially intro duced to distinguish between different hardware technologies. Gradually it shifted to both hardware and software as the total system consists of both of them.
First Generation Computers (1946-59)
First generation computers used Thermion valves or Vacuum tubes. These computes were large in size and writing programs on them was difficult. Some of the computers of this generation were: ENIAC: It was the first electronic computer built in 1946 at University of Pennsylvania, USA by John Eckert and John Mauchly. It was named Electronic Numerical Integrator and Calculator (ENIAC). The ENIAC was 30 x 50 feet long, weighed 30 tons, contained 18,000 vacuum tubes, 70,000 resistors, 10,000 capacitors and required 150 kilowatts of electricity. Today your favourite computer is many times as powerful as ENIAC, still the size is very small. EDVAC: It stands for Electronic Discrete Variable Automatic Computer and was developed in 1950. The concept of storing data and instructions inside the computer was introduced here. This allowed much faster operation since the computer had rapid access to both data and instructions. The other advantage of storing instruction was that computer could take logical decisions internally. Other Important Computers of First Generation EDSAC: It was developed by M.V. Wilkes at Cambridge University in 1949. UNIVAC-1: Eckert and Mauchly produced it in 1951 by Universal Accounting Computer setup. Followings were the major drawbacks of first generation computers: 1. They were quite bulky. 2. The operating speed was quite slow. 3. Power consumption was very high. 4. It required large space for installation. 5. They had no operating system. 6. The programming capability was quite low.
Second Generation Computers (1959-65)
Around 1959 an electronic device called Transistor replaced the bulky vacuum tubes in the first generation computer. A single transistor contained circuit produced by several hundred vacuum tubes. Thus the size of the computer got reduced considerably. Transistors therefore provided higher operating speed than vacuum tubes. They had no filament and require no heating. 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. The programming languages such as COBOL, FORTRAN were developed during this period. Some of the computers of the Second Generation were: IBM 1920: Its size was small as compared to First Generation computers and mostly used for scientific purpose. IBM 1401: Its size was small to medium and used for business applications. CDC 3600: Its size was large and used for scientific purpose. The salient features of this generation were: 1. relatively faster than the first generation computers. 2. smaller than the first generation computers 3. generated lower level of heat 4. more reliable 5. higher capacity of internal storage
Third Generation Computers (1965-75)
The third generation computers were introduced in 1964. They used Integrated Circuits (ICs). These ICs are popularly known as Chips. A single IC has many transistors, resistors and 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. The features of computers belonging to this generation were: 1. used tiny ICs 2. relatively very small in size 3. made use of operating system 4. high processing speed 5. more reliable 6. power efficient and high speed 7. use of high level languages 8. large memory 9. low cost
Fourth Generation Computers (1975- 1989)
(Intel’s 8088,80286,80386,80486 .., Motorola’s 68000, 68030, 68040, Apple II, CRAY I/2/X/MP etc) Fourth generation computers started around 1975. 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 a single chip. These computers are called microcomputers. Later very large scale Integrated Circuits (VLSIC) replaced LSICs. These integrated circuits are so advanced that they incorporate hundreds of thousands of active components in volumes of a fraction of an inch. Thus the computer, which was occupying a very large room in earlier days, can now be placed on a table. The salient features of this generation were: 1. very fast 2. very low heat generation 3 . smaller in size 4. very reliable 5. negligible hardware failure 6. highly sophisticated
Fifth Generation Computers (1989 to present)
(IBM notebooks, Pentium PCs-Pentium 1/2/3/4/Dual core/Quad core.. SUN work stations, Origin 2000, PARAM 10000, IBM SP/2) The computers, which can think and take decisions like human beings have been characterized as Fifth generation computers and are also referred as thinking machines. The speed is extremely high in fifth generation computer. Apart from this they can perform parallel processing. The concept of Artificial Intelligence has been introduced to allow the computer to take its own decision. It is still in a developmental stage. A lot of research and development work is going on in this area in United States and Japan but it will take some time before such machines are produced for use by the industry.
The salient features of this generation are:
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 30 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/…Windows7, 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.