The word computer is derived from the Latin word ‘computare’ which means “to calculate”, “to add” or “to count”. Computer is an electronic device which can calculate. Not only that computer is an electronic device, we can say computer is an electrical, electronics and programmable device which can take data or input from the user or external device, stores them in a memory (RAM or hard-drive), process those data and finally show that data as an desired output. Computers performs the task according to the instructions it was fed into, and those instructions are known as “programs”.
There are two types of computer which are
a) Analog Computer
b) Digital Computer
The development of computer has seen many changes and according to that changes and development, computer are divided as either analog or digital. In earlier time, computer are made up of mechanical and electrical components. Analog computer used to calculate a direct mechanical or electrical model of the problem as basis for calculation. At that time computer didn’t have programs so they had to be executed manually. The first modern analog computer was a tide-predicting machine invented by Sir William Thompson in 1872. The differential analyzer, a mechanical analog computer designed to solve differential equations by integration using wheel-and-disc mechanisms , was conceptualized in 1876 by James Thomson, the brother of the more famous Lord Kelvin.
Another type is Digital Computer. It is made up of various component mostly by transistor. By the development of the transistor computer has evolved rapidly. Digital computer has the characteristics like smaller size, faster processing, multitasking, multi-programming etc. It has also one more features, it can store the data that user provides for long term. Digital computer uses digital signal, thus it increases the security of the data because digital signal can be encrypted. It has programs so the work can be done very fast and easily. Programs are the set of instructions or rules which allow to perform some preferable work in given data or inputs.