Personal computers are now a very common item in many houses yet in 1955, there were only 250 computers in use throughout the world. In 1980, more than one million personal computers had been sold and by the mid-1980's, this figure had risen million. How did this about?
1. A computer in 1955 was very large and could not have fitted into a normal room in a normal sized house. They frequently burned out and had a tendency to attract moths into the system which short-circuited them.
2. . In the late 1950's, computers got smaller because one of its main components the valve - was replaced by the much smaller transistor. These made computers far more reliable and therefore businesses took a much greater interest in them.
3. By the mid-1960's, the microchip was replacing the transistor. A microchip could have several transistors on it. But being smaller, it lead again to a decrease in the size of computers.
4. By 1970, one microchip could contain 1000 transistors on it. In 1971, the microprocessor went on sale. It become cheaper and smaller. Developed by Ted Hoff of Intel.
5. In 1975, Bill Gates and Paul Allen developed a program for the Altair thal allowed people to write their own programs in BASIC program language. Their newly formed company was called Micro-Soft which was later changed to Microsoft.
6. In 1975, Apple Computers was founded by Steve Jobs and Steve Wozniac. Apple created the 'home/personal computer that could be used by anybody.
7. mage, could The personal computer was sealed in a neat plastic case, it had a keyboard, video unit and used removable floppy discs, Above all, it was much cheaper then before. The success of Apple Il established Apple Computers as the main player in the field of personal computers. By 1980, there were 1 million personal computers in the world.
IBM launched its own personal computer in 1981. Eventually 85% of all personal computers were to be IBM compatible. Microsoft won the contract to write the operating system for the IBM personal computer. Microsoft called its new operating system MS-DOS.
Computer Generations
Following are the main five generations of computers:
First Generation
The period of first generation was 1942-1954. The main features of first generation are:
1. Vacuum tube technology
2. Unreliable
3. Supported Machine language only
4. Very costly
5. Generate lot of heat normal
6. Huge size
Second Generation
Vacuum Tube ponents The period of second generation was 1952-1964. The main features of Second Generation mputers are: n them
1. Use of transistors
2. Reliable as compared to First generation computers
3. Smaller size as compared to First generation computers
4. Generate less heat as compared to generation computers
5. Faster than first generation computers
6. Still very costly
7. Support machine and assembly languages 
Third Generation
The period of third generation was 1964-1972. The main features of third generation are:
1. Integrated Circuit (IC) technology used
2. More reliable
3. Smaller size
4. Generate less heat
5. Faster
6. Lesser maintenance
7. Still costly
8. Support high level language
Fourth Generation
The period of Fourth Generation was 1972-1990. The main features of fourth generation are:
1. VLSI technology used
2. Very cheap
3 Portable and reliable
4. Use of PCs
5. Very small size
6. Pipeline processing
7. Concept of internet was introduced
8. Great developments in the fields of networks
9. Computers became easily available
Fifth Generation
The period of Fifth Generation is 1990-till date. The main features of Fifth Generation are:
1. ULSI (Ultra Large Scale Integration) technology used
2. Development of true artificial intelligence
3. Development of Natural language processing Advancement in Processing .
4. Advancement in parallel processing.
5. Advancement in Superconductor technology
6. More friendly interfaces with multimedia features
7. Availability of very powerful and compact computers at cheaper rates.
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