Encyclopedia of Computer Science and Technology

Licklider, Joseph Carl Robnett 277Licklider, Joseph Carl Robnett(1915–1990)AmericanComputer Scientist, PsychologistDynamic linking is an alternative approach to library use. The programis compiled with a reference to the library, but it is not linkedto the library code until the program is actually running. Since severaldifferent running programs can link to the same dynamic linklibrary (DLL), memory is saved.core language is kept simple because it doesn’t have to dealwith issues such as the actual storage of data in memorythat are dependent on the particular architecture of eachtype of machine. To “port” the language to a new machine,specialists in its architecture can implement the standardlibrary functions. In addition to the standard librariesincluded with the compiler, programmers are also free tocreate additional libraries to support particular applicationssuch as graphics.With a traditional library the library routines invokedin the source code are included in the final executable file.With most modern operating systems, however, many programsare active in memory at the same time (see multitasking).Storing the same commonly used routines(such as standard I/O) with each program wastes memory.Therefore, operating systems such as Microsoft Windowsuse dynamic linking. This means that instead of compilingthe library code into the program to create the executablefile, the program links to the library at execution time.If another program is using the library, the new programlinks to the same copy in memory rather than having tostore another copy. (Dynamically linked libraries [DLLs]include special code to keep track of the invocation of thelibrary functions by each separate program.)Further ReadingJosuttis, Nicolai M. The C++ Standard Library: A Tutorial and Reference.Upper Saddle River, N.J.: Addison-Wesley, 1999.Loosemore, Sandra, et al. GNU C Library Application Fundamentals.Boston: GNU Press, 2004.———. et al. GNU C Library System & Network Applications. Boston:GNU Press, 2004.Lundh, Fredrik. Python Standard Library. Sebastapol, Calif.:O’Reilly, 2001.Most of the early computer pioneers came from backgroundsin mathematics or engineering. This naturally ledthem to focus on the computer as a tool for computation andinformation processing. Joseph Licklider, however, broughtan extensive background in psychology to the problem ofdesigning interactive computer systems that could providebetter communication and access to information for users.Licklider was born on March 11, 1915, in St. Louis, Missouri.During the 1930s, he attended Washington Universityin St. Louis, earning B.A. degrees in psychology, mathematics,and physics. He then concentrated on psychology forhis graduate studies, earning an M.A. at Washington Universityand then receiving his Ph.D. from the University ofRochester in 1942.While at Rochester, Licklider participated in a studygroup led by Norbert Wiener, pioneer in the new field ofcybernetics, in the late 1940s. This brought him into contactwith emerging computer technology and its excitingprospects for the future. In turn, Licklider’s psychologybackground allowed him a perspective quite different fromthe mathematical and engineering background shared bymost early computer pioneers.Cybernetics emphasized the computer as a system thatcould interact in complex ways with the environment. Licklideradded an interest in human-computer interaction andcommunication. He began to see the computer as a sort of“amplifier” for the human mind. He believed that humansand computers could work together to solve problems thatneither could successfully tackle alone. The human couldsupply imagination and intuition, while the computer providedcomputational “muscle.” Ultimately, according to thetitle of his influential paper, it might be possible to achievea true “Man-Computer Symbiosis.”During the 1950s, Licklider taught psychology at theMassachusetts Institute of Technology, hoping eventually toestablish a full-fledged psychology department that wouldelevate the concern for what engineers call “human factors.”From 1957 to 1962 he also served in the private sector as avice president for engineering psychology at Bolt Beranekand Newman, the company that would become famous forpioneering networking technology.In 1962, the federal Advanced Research Projects Agency(ARPA) appointed Licklider to head a new office focusingon leading-edge development in computer science. Licklidersoon brought together research groups that includedin their leadership three of the leading pioneers in artificialintelligence: John McCarthy, Marvin Minsky, and AllenNewell (see artificial intelligence; McCarthy, John;and Minsky, Marvin). By promoting university access togovernment funding, Licklider also fueled the growth ofcomputer science graduate programs at major universitiessuch as Carnegie Mellon University, University of Californiaat Berkeley, Stanford University, and the MassachusettsInstitute of Technology.