Computer as defined in the simple words is nothing but a machine which takes an input, processes it as per our requirement and gives us a required output. They exist in different forms based on the function they perform. It is most commonly used as PC – a personal computer, its very user friendly and easy to use. Then there is Desktop which offers more storage and dynamism for less cost. There are Laptops to for people who would like to work while they are mobile, it is also known as portable computer where in we have a screen, keyboard, a mouse, hard drive etc. put together in a battery operated device. Another form is PDA – Personal Digital Assistant – a very light weight device with an impressive battery life. The other types of computers are workstation, server, mainframe, minicomputer and supercomputer.