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Four major high-level languages were developed at IBM: FORTRAN, GPSS, APL, and PL/I. In addition, significant contributions were made to formal methods for specifying language syntax and semantics, in particular, the Backus–Naur Form (BNF) and the Vienna Definition Language (VDL).
The development of FORTRAN (FORmula TRANslator), the first report on which was issued in 1954, had a great impact on the computer field in that it demonstrated that efficient object code could be produced by a compiler. FORTRAN is still the most widely used programming language for scientific, engineering, and mathematical problems.
GPSS (General Purpose Simulation System), a language developed in 1960 for simulating discrete events, is based on a block diagram notation and a simulation clock that advances in fixed-size steps. Although GPSS was used extensively in the following 20 years, it did not lead to the development of other major languages and its popularity decreased in favor of more flexible simulation languages such as Simula and SIMSCRIPT.
The APL notation, conceived around 1956 by Kenneth Iverson, led to a series of programming systems which culminated in the mid-1960s in an efficient interactive system supported by a special printing element that contained most of the unique language characters. APL is a high-level programming language that is famous for its conciseness and for its ability to handle vectors and matrices.
Work on PL/I started in 1963. It was designed with the goal of satisfying the needs of not only commercial and scientific programmers but also systems programmers. It included features from many other languages, such as ALGOL, COBOL, and FORTRAN. It also included facilities for dealing with storage allocation, task management, and exception handling. It was the first significant multipurpose language and introduced a large number of innovations.
BNF, a formal mechanism for defining a language syntax, was created by John Backus in 1959, with contributions from Peter Naur, and was used as a metalanguage for developing ALGOL 60. VDL represents the earliest attempt to formally define the semantics of a programming language. It was originally developed for PL/I and later applied to ALGOL and other languages.
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