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Programming Languages. A program is an encoding of computation in some programming languages Four basic programming language levels: machine language assembly language high-level language fourth-generation language Each CPU has its own specific machine language
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Programming Languages • A program is an encoding of computation in some programming languages • Four basic programming language levels: • machine language • assembly language • high-level language • fourth-generation language • Each CPU has its own specific machine language • The higher level languages were created to make programming easier
Genealogy of High Level Languages 1957 FORTRAN I 1958 ALGOL58 FORTRAN II 1959 LISP 1960 ALGOL60 COBOL 1961 FORTRAN IV 1962 1963 BASIC CPL 1964 SIMULA I 1965 1966 ALGOL-w PL/1 1967 SIMULA67 1968 ALGOL68 1969 BCPL 1970 B 1971 1972 Pascal Prolog C 1973 1974 1975 Scheme 1976 1977 FORTRAN77 1978 1979 1980 Smalltalk80 1981 1982 1983 Ada 1984 1985 Common Lisp C++ 1986
Main Components of A Language • Primitive expressions: the simplest entities the language is concerned with • Data • Procedures • Means of Combination: by which compound elements are built from simpler ones, e.g. (+ (* 3 5) (- 10 6)) • Means of Abstraction: by which compound elements can be named and manipulated as units.
Pretty-Printing (+ (* 3 (+ (* 2 4)(+ 3 5)))(+ (- 10 7) 6)) (+ (* 3 (+ (* 2 4) (+ 3 5))) (+ (- 10 7) 6))