In order to understand today's computers, it is important to study how computers evolved through time by discussing some of the major achievements. This section deals with the history of computers and identifies the major technological achievements of the four computer generations. Humans needed devices that could be used to perform calculations as early as the period when they kept animals and started to trade with other people. They realized the need to calculate and to record information. Many people agree that the history of calculation began with the Abacus around 5000 B.C.