Computer is a wonderful scientific invention. Charles Babez offered a primary concept of computer. On the basis of his concept the first automatic electronic computer was invented in 1946. And so he is called the father of computer. It is such an electronic machine which gives decision very swiftly by receiving masses of data and analysing them automatically. In accordance with the act and activities computer can be divided into three classes. They are analogue, digital and hy-breed computer. According to form and formation computer can be divided into four classes. They are Super computer, Mainframe computer, Mini computer and Microcomputer. Microcomputer is also called PC (Personal Computer). Computer has some specific parts. These are Input device, CPU (central processing unit) and Output device. However, computer is of great use to us. It is used in measuring daily routine work, trade and commerce, diagnosing diseases, entertainment, games and sports, transport, educational sector, researching space and what not. It has done a great wonder in inventing e-mail, internet and robot. Besides, its utility in controlling population, preparing budget, analysing natural calamity is very great. But computer is not of unmixed blessing. For its wide use unemployment problem is getting severe. It also causes various diseases to the users. Its ray is very harmful to them. By using computer, the users may lose eye-sight. Nevertheless, present lives cannot be led without computer. Truly speaking, modern civilisation is dependent on computer to a great extent.