generation of computer

Computer generation is the classification of computer into different groups according to their manufacturing date and the memory device & other hardware & software technology used in them. So generation of computer is a step in technology. It provides of the framework for the growth and development of more powerful & more useful computer system.
When computer generation goes higher i.e. from first to second , second to third & so on, then one can find that the speed, processing capability & storage capacity are increasing but size, power consumption, heat generation, cost & complexity are decreasing gradually. There are five generation of computer which are as follows:-
First Generation Computer

The computer which were made approximately between 1940&1956 AD are classified as the computer of first 

generation. All the computers made during the first generation had used the vacuum tubes or valves as memory device. Vacuum tubes were developed by Lee De forest in1908 & used later in computer. The first generation computer have the following features:-

1. The electronics circuit was based on vacuum tubes.
2. the computer of first generation were very big in size, unreliable & slower.
3. human operator had to set the switches before a program could run.
4. the operating[processing] speed was limited up to millisecond.
5. machine level languages was used for computer programming which made programming extremely difficult & time consuming.
6. punched cards were used as secondary storage.
7. the cost of the computer was very high.

The example of the first generation computer are Mark1 , ABC, ENIAC etc