Computers can divided into five generations depending upon the technologies used. These are following:
- First Generation (1942 – 1955)
- Second Generation (1955 – 1964)
- Third Generation (1964 – 1975)
- Fourth Generation (Since 1975)
- Fifth Generation (Since 1980)
First Generation (1942 – 1955)
Each computer had a different binary coded program called machine language that told it how to operate. This made the computer difficult to program and limited its versatility and speed.
This distinct features of first generation computers were:
Vacuum tubes were used to control and amplify the electronic signals.
There was no concept of operating system. Operating instructions were used to operate computers for specific tasks.
To operate the computer different binary coded programs were used. Example: ENIAC, EDVAC, EDSAC, etc. belongs to first generation computers.
The main advantages of first-generation computers etc.
- These computers were the fastest of their time.
- They were programmed using machine language.
- The electronic digital computers were introduced due to the vacuum technology.
The main disadvantages of first-generation computer were:
- Very big in size
- Not reliable
- Consumed large amount of energy
- Constant maintenance was required
- More heat generated and air-conditioning was required
- More costly
- Very slow in speed (data processing)
- It was difficult to write program for these generation computers, because they uses only machine language
- Limited commercial use
Second Generation Computer (1955 – 1964)
The transistor technology was used in second-generation computers. The electronic component transistor was invented in 1948 at Bell Laboratories. The transistor is smaller in size and more reliable than vacuum tube. Therefore, the transistor technology was used in computer in place of vacuum tube technology. Second generation computers replaced machine language with Assembly language allowing abbreviated programming codes to replace long difficult binary codes. More sophisticated high level languages such as COBOL (Common Business Oriented Language) and FORTRAN (Formula Translator) came into common use during this time.
The main advantage of second-generation computers as compared to first-generation computer are:
- Low in cost
- Smaller in size
- Fast in speed
- Less heat generated More reliable and accurate in calculations
- Consume low power etc.
- Used for commercial purpose
- Assembly language was introduced. This language is easy to write program than machine language
The main disadvantages of this generation computer are:
- Air-conditioned required
- Commercial production was difficult and these were very costly
- Constant (or frequent) maintenance required
- Only used for special purposes
Third Generation Computers (1964 – 1975)
The IC (Integrated Circuit) technology was used in third-generation computers. In a small IC chip (5 mm square size) a circuit is designed having large number of electronic components like transistors , capacitors, diodes, resistors etc. Initially, an IC contained only about ten to twenty components. Thus the IC technology was named as Small Scale Integration (SSI). The third-generation was based on IC technology and the computers were designed using this technology.
Another third generation development included the use of an operating system that allowed machines to run many different programs at once with a central program that monitored and coordinated the computer’s memory.
The main advantages of third-generation as compared to previous generations of computer were:
- Smaller in size
- Production cost was low
- Very fast in computational power
- More reliable
- Low power consumption
- Maintenance cost was low because failure rate of hardware was very low
- Magnetic disk, used for external storage
- More storage capacity
- Easily portable
- Easy to operate
- Upgraded easily
- Widely used for various commercial applications all over the world
- Lower heat generated
- High-level languages were commonly used
- Many input/output devices were introduced such as mouse and keyboard etc.
The main disadvantages of third-generation computers were:
- Air-conditioning required
- Highly sophisticated technology required for the manufacturer chips
Fourth Generation Computers (1975 onwards)
The microchip technology was introduced in this generation of computers. LSI (large scale integration) could it hundreds of components onto one chip. By the 1980’s Very Large Scale Integration (VLSI) squeezed hundreds of thousands of components onto a chip. Ultra Large Scale Integration (ULSI) increased that number into the millions. It increased their power, efficiency and reliability. Intel made a chip named 4004 in 1971 on which a central processing unit, memory and input / output controls were made.
IBM (International Business Machine) introduced its personal computer for use in 1981. The number of personal computers in use was two million in 1981 and increased to 5.5 million in 1982. Macintosh introduced an operating system that allowed users to move screen icons instead of typing instructions.
As smaller computers became more powerful, they could be linked-together or networked to share memory space, software information and communicated with each other as opposed to a mainframe or mini computer. Computers were linked together by using either direct wiring called a Local Area Network (LAN) or telephone lines called Internet.
The advantages of fourth-generation as compared to previous generation computers are:
- Smaller in size
- Production cost is very low
- Very reliable
- Hardware failure is negligible
- Easily portable because of their small size
- Totally general purpose
- Air conditioning is not compulsory
- Very high processing speed
- Very large internal and external storage capacity
- Used advanced input & output devices such as optical readers, laser printers, CD-ROM/DVD-ROM drives etc.
The main disadvantage of fourth-generation computers is:
- Highly sophisticated technology required for the manufacturer of microprocessor chips
Fifth Generation Computers (In process)
The main drawback of first to fourth generation computers is that the computers have not their own thinking power. These are totally depending upon the instructions given by the users.
Fifth generation computers are supposed to be the ideal computers, but do not exist. The scientists are working to design such computers that will have the following features.
- Having their own thinking power
- Making decisions themselves
- Having capabilities of learning
- Having capabilities of reasoning
- Having large capacity of internal storage
- Having extra high processing speed
- Having capabilities of parallel processing
In these computers following technologies will be used:
ULSIC (Ultra Large Scale Integrated Circuits) technology
Artificial Intelligence (AI) technology also called the knowledge Processor. The AI means automatic programs that let the machines to think and decide themselves. The programming languages LISP (List Processor) and PROLOG (Programming with Logic) are used for artificial intelligence. The scientists at ICOT in Japan use the PROLOG to develop the Artificial Intelligence software.