The development of computers began in the late 1940s with huge mainframes that used vacuum tube technology. The second generation of computers were built with discrete transistors, from the mid-1950s through the mid-1960s. Third-generation computers were built using integrated circuits after the mid-1960s; during this time period, minicomputers were developed. The fourth generation of computers are the microcomputers which use large-scale integration or very large-scale integration. In 1973, the Xerox Corporation Palo Alto Research Center (PARC) built the first desktop computer, called the "Alto", that implemented a bitmapping process and utilized a mouse pointer. The fifth generation of computers, beginning in the late 1990s, uses quantum mechanics, and are expected to extend and expand the application of artificial intelligence (AI). See quantum, IAS, ENIAC, MANIAC, Mark 1, stone age, hardware, bus, SSI, chip, disc, markup, database, file system, software, program, platform, interface, analog, cybernetics, language.