Generations of computers:

First generation of computer(1942-55): Vacuum Tubes :

Vacuum Tube

These computers that used vacuum tubes, which was only available technology those days.

These computers made use of electronic digital circuits and were the fastest calculating device of their time. They could perform the instructions in milliseconds. This is why the technology of vacuum tubes was accepted.

They were to big in size and required large rooms for installation.

As a large number of vacuum tubes were connected, they generated lot of heat. Therefore, these computers required continuous maintenance and cooling with the help of large AC's .

They had poor reliability as they could produce inaccurate result sometimes.

They used batch processing techniques and use punched card and paper-tape as secondary storage. Thus all problems faced in batch processing were also faced.

They performed slow input/output operations.

These computers were programmed by machine language that was difficult to design.

These computers had limited commercial use.

Second generation of computers(1955-64): Transistor :

Transistor

Manual assembly of individual into a functioning unit was required.

They were about 10 times faster than the first generation computers.

They were highly reliable and lesser prone to hardware failures.

Lesser amount of heat was generated but still air conditioning was required.

They consumed lesser power.

They were much smaller in size and required lesser space for installation.

The capacity to store data using magnetic tapes and magnetic disk increased.

They were much easier to program and had commercial usage due to high level procedural languages like FORTRAN, COBOL were available.

The commercial production of second generation computers was limited and costly.

As the circuitry was still complex so proper knowledge was required. Only technicians could handle these.

Third generation of computers(1964-75):IC:

Integrated Circuit

The IC's used were more powerful and smaller than second generation computers.

They were more reliable and lesser prone to errors. They had low maintenance cost.

Being smaller in size they required lesser space for installation.

The storage space available in these computers was much more than earlier computers and had faster access.

They supported the concept of timesharing.

Development and introduction of minicomputers took place in this generation.

Development of standardized high level languages like PL/1, PASCAL, BASIC etc.

The cost of preparation and maintenance of these computer was very less.

They had much wider scientific commercial usage.

There was lesser heat dissipation, still air-conditioning was required.

The development of IC's was a tedious task and required sophisticated technology.

Fourth generation of computers(1975=91): Microprocessors :

Much smaller in size than mainframe of third generation computers.

No air-conditioning was required for PC's .

Consumed less power.

More reliable and lesser prone to hardware failure.

Increased costs of software and lower costs of hardware.

Faster access to larger memory.

No manual assembly of components was required.

Use of high level languages allowed program to be transferred from one computer to another.

Pipeline processing.

Used in application development by users.

New operating systems introduced that were user friendly.

Fifth generation computers (Present and Beyond)- Artificial Intelligence :

Game Playing- Programming computers to play games such as chess and checkers.

Programming computers to play games such as chess and checkers. Expert Systems - Programming computers to make decisions in real life situations(For example, some expert systems help doctors diagnose diseases based on symptoms)

Programming computers to make decisions in real life situations(For example, some expert systems help doctors diagnose diseases based on symptoms) Natural Language - Programming computers to understand natural human languages.

Programming computers to understand natural human languages. Neural Networks - Systems that simulate intelligence by attempting to reproduce the types of physical connections that occur in animal brains.

Systems that simulate intelligence by attempting to reproduce the types of physical connections that occur in animal brains. Robotics - Programming computers to see and hear and react to other sensory stimuli.

Computers can be classified according to the major changes in the development of the computer industry. These significant development in the hardware technologies (and now software technologies also) in a generation. Thus , 'Generation' is a step in technology.There are five generations of computers ;The computers in this generation used vacuum tubes as circuitry and magnetic drums (a metal coated with magnetic iron-oxide material) for memory. A vacuum is a glass device that used filaments as a source of electrons that could control and amplify electronic signals. They were about the size of a small electric bulb and produced a lot of heat. As a result, they were enormous, literally taking up entire rooms and costing a fortune to run. These were inefficient materials that generated a lot of heat, sucked huge electricity and subsequently generated a lot of heat which caused ongoing breakdowns. The vacuum tubes could perform computations in milliseconds and were the only available high speed electronic switching device in those days.ENAMIC, EDVAC, UNIVAC, IBM-701, IBM-650 etc.To overcome the difficulties encountered while with working with computers based on vacuum tubes, a new electronic switching device called transistor was made. The transistor that were made of semiconductor material were highly reliable as compared to vacuum tubes since they had no filaments to burn . Thus making computer smaller, faster, cheaper and less heavy on electricity use.Transistor-driven machines were the first computers to store instructions into their memories-moving from magnetic drum to magnetic core technology. They were used to construct large random access memories. With the introduction of magnetic tapes, their capacity to store data increased many folds. However, they still relied on punched card for input/printouts.Honeywell 400, IBM 7094, CDC 1604, CDC 3600, UNIVAC 1108 etc.In third generation of computers, transistors were being miniaturized and put on silicon chips(called semiconductors). These chips were called integrated circuit or IC's. The various components were interconnected inside the chip to form an electronic circuit. The chip was mounted on a metal or plastic package, and connections are welded to external pins to form the IC. Initially, the IC's contained only about ten to twenty components. This technology was named Small Scale Integration(SSI). Later advancements were made and was made possible to integrate about hundred components on a single chip. This technology was called Medium Scale Integration(MSI).PDP-8, PDP-11, ICL 2900, IBM 360, IBM 370 etc.The fourth generation computer used ICs that could integrate over 30000 components(transistor, diodes etc.) into a single chip. This generation was called Large Scale Integration(LSI). Later, it was made possible to integrate about one lakh or more electronic components on a single chip. This progress led to the development of a microprocessor. It contained all circuits needed to perform arithmetic, logic and control circuits. The technology in which very large number of circuits were grouped was called Very Large Scale Integrations(VLSI).IBM 4341, DEC 10, STAR 1000, PUP 11 etc.Fifth generation computing devices, based on artificial intelligence, are still development though there are some applications , such as voice recognition, that are still being used today.Artificial Intelligence is a branch of computer science concerned with making computers behave like humans. Artificial Intelligence includes :Currently, no computers support full artificial intelligence. The concept of nanotechnology is also emerging in this generation.