Encyclopedia of Computer Science and Technology

410 roboticsMac. The MIT computer students, the original “hackers” (inthe positive meaning of the term), emphasized a cooperativeapproach to designing tools for writing programs. This,too, was quite different from IBM’s highly structured andcentralized approach.Unfortunately, the Multics project itself grew increasinglyunwieldy. Bell Labs withdrew from the Multics projectin 1969. Ritchie and his colleague Ken Thompson thendecided to apply many of the same principles to creatingtheir own operating system. Bell Labs wasn’t in a mood tosupport another operating system project, but they eventuallylet Ritchie and Thompson use a DEC PDP-7 minicomputer.Although small and already obsolete, the machinedid have a graphics display and a Teletype terminal thatmade it suitable for the kind of interactive programmingthey preferred. They decided to call their system UNIX,punning on Multics by suggesting something that was simplerand better integrated.Instead of designing from the top down, Ritchie andThompson worked from the bottom up. They designed away to store data on the machine’s disk drive (see file), andgradually wrote the necessary utility programs for listing,copying, and otherwise working with the files. Thompsondid the bulk of the work on writing the operating system,but Ritchie did make key contributions such as the idea thatdevices (such as the keyboard and printer) would be treatedthe same way as other files. Later, he reconceived data connectionsas “streams” that could connect not only files anddevices but applications and data being sent using differentprotocols. The ability to flexibly assign input and output, aswell as to direct data from one program to another, wouldbecome hallmarks of UNIX.When Ritchie and Thompson successfully demonstratedUNIX, Bell Labs adopted the system for its internal use.UNIX turned out to be ideal for exploiting the capabilitiesof the new PDP-11 minicomputer. As Bell licensed UNIX tooutside users, a unique community of user-programmersbegan to contribute their own UNIX utilities (see opensourcemovement).In the early 1970s, Ritchie also collaborated with Thompsonin creating C, a streamlined version of the earlier BCPLand CPL languages. C would be a “small” language thatwas independent of any one machine but could be linkedto many kinds of hardware thanks to its ability to directlymanipulate the contents of memory. C became tremendouslysuccessful in the 1980s. Since then, C and its offshoots C++and Java became the dominant languages used for most programmingtoday.Ritchie still works at Bell Labs’s Computing SciencesResearch Center. (When AT&T spun off many of its divisions,Bell Labs became part of Lucent Technologies.)Ritchie developed an experimental operating system calledPlan 9 (named for a cult sci-fi movie). Plan 9 attempts totake the UNIX philosophy of decentralization and flexibilityeven further, and is designed especially for networkswhere computing resources are distributed.Ritchie has received numerous awards, often givenjointly to Thompson. These include the ACM Turing Award(1985), the IEEE Hamming Medal (1990), the TsutomuKanai Award (1999), and the National Medal of Technology(also 1999).Further ReadingDennis Ritchie Home Page. Available online. URL: http://www.cs.bell-labs.com/who/dmr/. Accessed August 27, 2007.Kernighan, B. W., and Dennis M. Ritchie. The C ProgrammingLanguage. Upper Saddle River, N.J., Prentice Hall, 1978. (Asecond edition was published in 1989.)Lohr, Steve. Go To. New York: Basic Books, 2001.Plan 9 from Bell Labs. 4th ed. Available online. URL: http://plan9.bell-labs.com/plan9/. Accessed August 19, 2007.Ritchie, Dennis M., and Ken Thompson. “The UNIX Time-SharingSystem.” Communications of the ACM 17, 7 (1974): 365–375.Slater, Robert. Portraits in Silicon. Cambridge, Mass.: MIT Press,1987.roboticsThe idea of the automaton—the lifelike machine that performsintricate tasks by itself—is very old. Simple automatonswere known to the ancient world. By the 18th century,royal courts were being entertained by intricate humanlikeautomatons that could play music, draw pictures, or dance.A little later came the “Turk,” a chess-playing automatonthat could beat most human players.However, things are not always what they seem. Thetrue automatons, controlled by gears and cams, could playonly whatever actions had been designed into them. Theycould not be reprogrammed and did not respond to changesin their environment. The chess-playing automaton held aconcealed human player.True robotics began in the mid-20th century and hascontinued to move between two poles: the pedestrian butuseful industrial robots and the intriguing but tentativecreations of the artificial intelligence laboratories.Industrial RobotsIn 1921, the Czech playwright Karel Capek wrote a playcalled R.U.R. or Rossum’s Universal Robots. Robot is a Czechword that has been translated as work(er), serf, or slave. In theplay the robots, which are built by factories to work in otherfactories, eventually revolt against their human masters.During the 1960s, real robots began to appear in factorysettings (see also Engelberger, Joseph). They were an outgrowthof earlier machine tools that had been programmedby cams and other mechanisms. An industrial robot is basicallya movable arm that ends in a “hand” called an endeffector. The arm and hand can be moved by some combinationof hydraulic, pneumatic, electrical, or mechanicalmeans. Typical applications include assembling parts,welding, and painting. The robot is programmed for a taskeither by giving it a detailed set of commands to move to,grasp, and manipulate objects, or by “training” the robot bymoving its arm, hand, and effectors through the requiredmotions, which are then stored in the robot’s memory. Bythe early 1970s, Unimation, Inc. had created a profitablebusiness from selling its Unimate robots to factories.The early industrial robots had very little ability torespond to variations in the environment, such as the “work