Computers were first invented to process text data and execute certain large numerical calculations with greater accuracy. But later on the depth of usage of computers increased, and man found that computers could play a vital role in everyday life. The ease with which computers can process data, store and retrieve it painlessly has made them inevitable in office and business environments. The areas of applications of computers are confined only by limitations on human creativity and imagination. Accessing information from various parts of the world is possible by the implementation of computers in networking technologies. Some applications like internet are widely used. Therefore, it is essential for every educated person today to know about a computer, its strength, its weakness and its internal structure. Let us learn them in detail in this chapter.