a medium allowing humans and computers to communicate an abstraction of the real world a notation for expressing algorithms the set of all syntactically correct programs CS/421 is not a programming course! CS/421 is not a survey of languages course!

Classification by “Power”  machine language - a program instruction is a number - programs are “understood” by computer hardware  assembler language - a program instruction is a mnemonic version of the corresponding machine instruction  high-level language - language constructs are designed with the programmer in mind  parallel language - a program is a group of tasks that execute simultaneously

Classification by Intended Application  general purpose … e.g. PL/1  scientific/engineering applications … e.g. FORTRAN  business applications … e.g.s COBOL, RPG  systems programming … e.g.s C, PL/S, Bliss  real time systems … e.g.s Ada, Jovial  list processing … e.g.s LISP, SLIP, Scheme  string processing … e.g.s Snobol, Icon  set processing … e.g. SETL  Web applications … e.g. Java  O.S. script programming … e.g.s Perl

Classification by User Interface  compiled Each program (the source code) must be translated into machine language form for execution.  interpreted The source code instructions are analyzed individually as they are executed.

Classification by Paradigm  imperative / procedural programming  program = sequence of instructions (usually including loops & procedures)  variables & assignments used liberally  key control structure: repetition (while/for)  key data structure: array  examples: Ada, C, Cobol, FORTRAN, Pascal, PL/1  functional / applicative programming  program = a function to be evaluated  key control structure: recursion  key data structure: list  examples: LISP, Scheme, ml

Classification by Paradigm (continued)  object-oriented programming  program = sequence of operations (methods) applied to objects  an object incorporates both data and associated operations  examples: Smalltalk, Eiffel, Java, C#  logic-based / relational programming  program = a collection of rules and goals  program execution is based on theorem proving concepts  example: Prolog

languageyearauthor(s)intended purpose FORTRAN1957J. Backus/IBMscientific LISP1958McCarthy (MIT)list processing (A.I.) ALGOL 58/ Intn’l committeegeneral COBOL1959Hopper/committeebusiness D.P. APL1960 Iverson/Harvard/IBMmatrices/scientific SNOBOL1962Griswold/Bell Labsstring processing BASIC1963Kemeny & Kurtzeducation PL/11963SHARE Com./IBMgeneral Simula1963Dahl et. al.general/simulation ALGOL Intn’l committeegeneral Bliss1971Wulf/CMUsystems programming Pascal1971Wirth/ETC-Zurichgeneral/education Prolog1972Colmerauer/Kowalskilogic-based (A.I.)

languageyearauthor(s)intended purpose C1972Ritchie/Bell Labssystems programming Conc.Pascal1975Hansen/CA-Techparallel programming Scheme1975 Steele/Sussman/MITlists/A.I. Euclid1977Committeeverifiable prog. Gypsy1977U of TXverifiable prog. Modula-21977Wirth/ETCgeneral ML1978Milner/EdinburghMachine-assisted proof Ada1979DOD committeereal-time Smalltalk1980Kay/Xerox PARCobject-oriented C++1986Stroustrup/Bell Labsobject-oriented C Eiffel1990Bertrand Meyerobject-oriented Java1994Gosling/SunWeb/object-oriented C#2001Microsoftbasis for.net