The Generations Of Modern Computer

Q5. Write a note on all five generations of computers discussing their characteristics. Also give examples of computers belonging to each generation.

Ans. First Generation Computers (1949-55)

The first generation computers used thermionic values (vacuum tubes) and machine language was used for giving instructions. The first generation computers used the concept of ‘stored program’. The computers of this generation were very large size and their programming was a difficult task. Some computers of this generation are being given below:

  1. ENIAC

This was the first electronic computer developed in 1946 by a team lead by Prof. Eckert and Mauchly at the University of Pennsylvania in U.S.A. This computer, called Electronic Numerical Integrated And Calculator, used high speed vacuum tube switching devices. It has a very small memory and it was used for calculating the trajectories of missiles. It took 200 microseconds for addition and about 2800 microseconds for multiplication. This giant machine was 30X50 feet long, weighed 30 tons, contained 18,000 vacuum tubes, 70,000 resistors,  10,000 capacitors, 6000switches, used 150,000 watts of electricity, and cost S400,000. When ENIAC was built, it was 5000 times faster than the closest competitor, the Harserd MARK-I.

  1. EDVAC

The binary arithmetic was used in the construction of a computer called the Electronic Discrete Variable Automatic Computer (EDVAC), completed in 1950. The Von Neumann concept of stored program (in which the machine instructions are stored with data internally) was also applied in EDVAC. With this the operation became faster since the computer could rapidly access both the program and data.

  1. EDSAC

The EDSAC, short for Electronic Delay Storage Automatic Computer was built by Prof. M.V. Wilkes at Cambridge University in 1949 and used mercury delayed lines for storage. It also used Neumann concept ‘stored program’. This allowed easy implementation of program loops.


Commercial production of stored program electronic computers began in the early 50’s. One such computer was UNIVAC-I built by Univac division of Remington Rand and delivered in 1951. This computer also used vacuum tubes.


Initial applications of computers those days were in science and engineering but with the advent of UNIVAC I, the prospects of commercial application were perceived.

Though the first generation computers were welcomed by Govt. and Universities as they greatly helped them in these tasks, however, the first generation computers suffered from some ‘big’ limitations like slow operating speed, restricted computing capacity, high power consumption, short mean time between failures, very large space requirement and limited programming capabilities. Further researches in this line aimed at removal of these limitations.


Second Generation Computers (1956-65)

A big revolution in electronics took place with the invention of transistors by Bardeen, Brattain and Shockley in 1946. Transistors were highly reliable compared to tubes. They occupied less space and required only 1/10 of the power required by tubes. Also they took 1/10 time (switching from 0 to 1 or 1 to 0) needed by tubes and were ten times cheaper than those using tubes.

Another major event during this period was the invention of magnetic core and development of magnetic disk for storage. These are tiny ferrite rings (0.02 inch diameter) that can be magnetized in either clockwise or anti-clockwise direction. The two directions represent 0 and 1. Magnetic cores were used to construct large random access memories.

The second generation computers began with the advent of transistorized circuitry, invention of magnetic core and development of magnetic disk storage devices. These new developments made these computers much more reliable.

The increased reliability and availability of large memories paved the way for the development of high level languages (HLL) such as FORTRAN, COBOL, Algol and Snobol etc. With speedy CPUs and the advent of magnetic tape and disk storage, operating systems came into being. Batch operating systems ruled the second generation computers.

Commercial applications rapidly developed during this period and more than 80% of these computers were used in business and industries in the applications like payroll, inventory control, marketing, production planning etc.


Third Generation Computers (1966-75)

The third generation’s computers replaced transistors with ‘Integrated Circuits’ known popularly as chips. The ‘Integrated Circuit’ or I.C. was inverted by Jack Kilby at Texas Instruments in 1958.

An I.C. is wafer tin slice of extremely purified silicon crystals. A single I.C. has many transistors, resistors and capacitors along with the associated circuitry encapsulated in a small package with many leads.

From small scale integrated (SSI) circuits which had about 10 transistors per chip, technology developed to medium scale integrated, (MSI) circuits with 100 transistors per chip. The size of main memories reached about 4 megabytes. Magnetic disk technology also improved and it became feasible to have drive having capacity up to 100 MBs. The CPUs because much more powerful with the capacity of carrying out 1 million instructions per second (MIPS).

The third generation computers using integrated circuits proved to be highly reliable, relatively inexpensive, and faster. Less human labor was required at assembly stage. Examples of some mainframe computers developed during this generation are: IBM-360 series, ICL-1900 series, IBM-370/168, ICL-2900, Honeywell Model 316, Honeywell-6000 series. Some mini computers developed during this phase are: ICL-2903 manufactured by International Computers Limited, CDC-1700 manufactured by Control Data Corporation and PDP-11/45 (Personal Data Processor – 11/45)

Computers these days found place in other areas like education, survey, small businesses, estimation, analysis etc. along with their previous usage area that is, scientific and engineering.


Fourth Generation Computers (1976-present)

The advent of the microprocessor chip marked the beginning of the fourth generation computers. Medium scale integrated (MSI) circuits yielded to Large and Very Large Scale Integrated (VLSI) circuits packing about 50000 transistors in a chip. Semiconductor memories replaced magnetic core memories. The emergence of the microprocessor (CPU on a single chip) led to the emergence of extremely powerful personal computers. Computer costs came down so rapidly that these found places in most offices and homes. The faster accessing and processing speeds and increased memory capacity helped in development of much more powerful operating system.

The second decade (1986-present) of the fourth generation observed a great increase in the speed of microprocessors and the size of main memory. The speed of microprocessors and the size of main memory and hard disk went up by a factor of 4 every 3 years. Many of the mainframe CPU features became part of the microprocessor architecture in 90s. In 1995 the most popular CPUs were Pentium, Power PC etc. Also RISC (Reduced Instruction Set Computers) microprocessors are preferred in powerful servers for numeric computing and file services.

The hard disks are available of the six up to 80 GB. For large disks RAID technology (Redundant Array of Inexpensive Disks) gives storage up to hundreds of GB. The CDROMS (Compact Disk-Read Only Memory) are also becoming popular day by day. The CDROMs of today can store up to 650 MB information.

The computer networks came of age and are one of the most popular ways of interacting with computer chains of millions of users. The computers are being applied in various areas like simulation, visualization, Parallel computing, virtual reality, Multimedia etc.


Fifth Generation Computers (Coming Generation)

Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. The use of parallel processing and supercomputers is helping to make artificial intelligence a reality. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and self-organization.

The most noticeable characteristics of these computers will be the ability to apply previously gained knowledge, draw conclusions and then execute a task. The computer will, in short, simulate the human ability to reason.

Computers will have to be able to classify information, search large databases rapidly, plan, apply the rules which humans regard as clear thinking, make decision and learn from their mistakes. Input devices for future computers could also include speech and visual recognition.


Applications for Fifth-Generation Computers

Intelligent robots that could ‘see’ their environment (visual input – for example, a video camera) and could be programmed to carry out certain tasks without step-by-step instructions. The robot should be able to decide for itself how the task should be accomplished, based on the observations it made of its environment.


Applications examples of 5th generation computers are:

Intelligent systems that could control the route of a missile and defense-systems that could fend off attacks; Word processors that could be controlled by means by speech recognition; Programs that could translate documents from one language to another.



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