In the first generation (Vacuum Tubes-1940-1956) the vacuum tubes were used as the basic components for memory in the first generation computers. Punch cards, magnetic tape, and paper Regarding the main features of the first generation computers, in general, their sizes were very large (non-portable), their energy consumption and heat release to the environment were too high. Those computers were relatively very slow (solve only one problem at a time) and quite expensive. They used machine code as the programming language and used batch processing operating system. In the second generation (Transistors-1956 - 1963) transistors replaced vacuum tubes in the second generation computers. Those computers were cheaper, consuming less power, smaller in size, more reliable and faster than the first generation computers. In this generation, magnetic cores were used for the primary memory and magnetic tape and magnetic disks for secondary storage devices. Low-level programming languages such as assembly language, batch processing and multiprogramming operating system were used as well. The computers belonging to the third generation (Integrated Circuits-1964- 1971) used integrated circuits instead of transistors. These computers were smaller in size, more reliable, faster and more efficient than the previously developed ones. In this generation, remote processing, high- level programming languages, multiprogramming operating system were used. The fourth generation computers (Microprocessors-1971-Present used Very or even thousands of integrated circuits were built onto a single silicon chip to form a microprocessor. These computers became more compact, powerful, portable, reliable, cheaper, and easily available. Real time networks, time-sharing, distributed operating system and high-level languages were used in this generation. The fifth generation computers (Artificial Intelligence-Present and Future), based on artificial intelligence, are still in development, though certain applications such as computer vision and pattern recognition are being used today. The use of parallel processing enabled hardware and software allow computers to perform artificial intelligence based tasks. It is evident that quantum computation and nanotechnology would change the computers dramatically in the near future. The correct answer is Choice B.