Encyclopedia of Computer Science and Technology

290 mainframeMaes has participated in many high-profile conferencessuch as AAAI (American Association for Artificial Intelligence)and ACM Siggraph, and her work has been featuredin numerous magazine articles. She was one of 16 modern“visionaries” chosen to speak at the 50th anniversary of theACM. She has also been repeatedly named by Upside magazineas one of the 100 most influential people for developmentof the Internet and e-commerce. Time Digital featuredher in a cover story and selected her as a member of its“cyber elite.” Newsweek put her on its list of 100 Americansto be watched for in the year 2000. That same year the MassachusettsInteractive Media Council gave her its LifetimeAchievement Award.Further ReadingD’inverno, Mark, and Michael Luck, eds. Understanding Agent Systems.2nd. ed. New York: Springer Verlag, 2003.Maes, Pattie. “Intelligence Augmentation: A Talk with PattieMaes.” Available online. URL: http://www.edge.org/3rd_culture/maes./ Accessed May 5, 2007.Software Agents group at MIT Media Lab. http://agents.mit.edu.Accessed May 5, 2007.mainframeIn the era of vacuum tube technology, all computers werelarge, room-filling machines. By the 1960s, the use of transistors(and later, integrated circuits), enabled the productionof smaller (roughly, refrigerator-sized) systems (seeminicomputer). By the late 1970s, desktop computers werebeing designed around newly available computer chips (seemicroprocessor). Although they, too, now use integratedcircuits and microprocessors, the largest scale machines arestill called mainframes.The first commercial computer, the UNIVAC I (see Eckert,J. Presper and Mauchly, John) entered service in1951. These machines consisted of a number of large cabinets.The cabinet that held the main processor and mainmemory was originally referred to as the “mainframe”before the name was given to the whole class of machines.Although the UNIVAC (eventually taken over by SperryCorp.) was quite successful, by the 1960s the quintessentialmainframes were those built by IBM, which controlledabout two-thirds of the market. The IBM 360 (and in the1970s, the 370) offered a range of upwardly compatible systemsand peripherals, providing an integrated solution forlarge businesses.Traditionally, mainframes were affordable mainly bylarge businesses and government agencies. Their mainapplication was large-scale data processing, such as thecensus, Social Security, large company payrolls, and otherapplications that required the processing of large amountsof data, which were stored on punched cards or transferredto magnetic tape. Programmers typically punched theirCOBOL or other commands onto decks of punched cardsthat were submitted together with processing instructions(see job control language) to operators who mountedthe required data tapes or cards and then submitted theprogram cards to the computer.By the late 1960s, however, time-sharing systems allowedlarge computers to be partitioned into separate areas so thatthey can be used by several persons at the same time. Thepunched cards began to be replaced by Teletypes or videoterminals at which programs or other commands could beentered and their results displayed or printed. At aboutthe same time, smaller computers were being developed byDigital Equipment Corporation (DEC) with its PDP series(see minicomputer).With increasingly powerful minicomputers and later,desktop computers, the distinction between mainframe,minicomputer, and microcomputer became much less pronounced.To the extent it remains, the distinction today ismore about the bandwidth or amount of data that can beprocessed in a given time than about raw processor performance.Powerful desktop computers combined into networkshave taken over many of the tasks formerly assignedto the largest mainframe computers. With a network, evena large database can be stored on dedicated computers (seefile server) and integrated with software running on theindividual desktops.Nevertheless, mainframes such as the IBM System/390are still used for applications that involve processing largenumbers of transactions in near real-time. Indeed, manyof the largest e-commerce organizations have a mainframeat the heart of their site. The reason is that while the rawprocessing power of high-end desktop systems today rivalsthat of many mainframes, the latter also have high-capacitychannels for moving large amounts of data into and out ofthe processor.Early desktop PCs relied upon their single processor tohandle most of the burden of input/output (I/O). AlthoughPCs now have I/O channels with separate processors (seebus), mainframes still have a much higher data throughput.The mainframe can also be easier to maintain than anetwork, since software upgrades and data backups canbe handled from a central location. On the other hand, aThe IBM System/360 was the most successful mainframe in computerhistory. It was actually a “family” of upwardly compatiblemachines. (IBM Corporate Archives)