pascal

Pascal: see programming language.

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pascal

Unit of pressure, abbreviated Pa, in the International System of Units. Named for Blaise Pascal, the unit is a pressure of one newton per square meter (1 N/m²). It is inconveniently small for many purposes, and the kilopascal (kPa), 1,000 N/m², is more commonly used in engineering work (1 lb per sq in. equals 6.895 kPa).

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Pascal

Computer programming language named for Blaise Pascal and based partly on ALGOL. It was developed by Niklaus Wirth of Zurich's Federal Institute of Technology in the late 1960s as an educational tool for systematic teaching of programming, with fast, reliable compilers. It was made available to the public in 1974 and was used by many universities for the next 15 years. Pascal strongly influenced languages developed later, such as Ada. Complex data structures and algorithms can be described concisely by Pascal, and its programs are easy to read and debug.

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A high-level programming language developed by Swiss professor Niklaus Wirth in the early 1970s and named after the French mathematician, Blaise Pascal. It is noted for its structured programming, which caused it to achieve popularity initially in academic circles. Pascal has had strong influence on subsequent languages, such as Ada, dBASE and PAL. See Turbo Pascal.

Pascal is available in both interpreter and compiler form and has unique ways of defining variables. For example, a set of values can be stated for a variable, and if any other value is stored in it, the program generates an error at runtime. A Pascal set is an array-like structure that can hold a varying number of predefined values. Sets can be matched and manipulated providing powerful non-numeric programming capabilities.

The following Turbo Pascal example converts Fahrenheit to Celsius:

   program convert;
   var
   fahr, cent : real;
   begin
    write('Enter Fahrenheit ');
    readln(fahr);
    cent := (fahr - 32) * 5 / 9;
    writeln('Celsius is ',cent)
   end.

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(language)

Pascal - (After the French mathematician Blaise Pascal (1623-1662)) A programming language designed by Niklaus Wirth around 1970. Pascal was designed for simplicity and for teaching programming, in reaction to the complexity of ALGOL 68. It emphasises structured programming constructs, data structures and strong typing. Innovations included enumeration types, subranges, sets, variant records, and the case statement. Pascal has been extremely influential in programming language design and has a great number of variants and descendants. ANSI/IEEE770X3.97-1993 is very similar to ISO Pascal but does not include conformant arrays. ISO 7185-1983(E). Level 0 and Level 1. Changes from Jensen & Wirth's Pascal include name equivalence; names must be bound before they are used; loop index must be local to the procedure; formal procedure parameters must include their arguments; conformant array schemas. An ALGOL-descended language designed by Niklaus Wirth on the CDC 6600 around 1967--68 as an instructional tool for elementary programming. This language, designed primarily to keep students from shooting themselves in the foot and thus extremely restrictive from a general-purpose-programming point of view, was later promoted as a general-purpose tool and, in fact, became the ancestor of a large family of languages including Modula-2 and Ada (see also bondage-and-discipline language). The hackish point of view on Pascal was probably best summed up by a devastating (and, in its deadpan way, screamingly funny) 1981 paper by Brian Kernighan (of K&R fame) entitled "Why Pascal is Not My Favourite Programming Language", which was turned down by the technical journals but circulated widely via photocopies. It was eventually published in "Comparing and Assessing Programming Languages", edited by Alan Feuer and Narain Gehani (Prentice-Hall, 1984). Part of his discussion is worth repeating here, because its criticisms are still apposite to Pascal itself after ten years of improvement and could also stand as an indictment of many other bondage-and-discipline languages. At the end of a summary of the case against Pascal, Kernighan wrote: 9. There is no escape This last point is perhaps the most important. The language is inadequate but circumscribed, because there is no way to escape its limitations. There are no casts to disable the type-checking when necessary. There is no way to replace the defective run-time environment with a sensible one, unless one controls the compiler that defines the "standard procedures". The language is closed. People who use Pascal for serious programming fall into a fatal trap. Because the language is impotent, it must be extended. But each group extends Pascal in its own direction, to make it look like whatever language they really want. Extensions for separate compilation, Fortran-like COMMON, string data types, internal static variables, initialisation, octal numbers, bit operators, etc., all add to the utility of the language for one group but destroy its portability to others. I feel that it is a mistake to use Pascal for anything much beyond its original target. In its pure form, Pascal is a toy language, suitable for teaching but not for real programming. Pascal has since been almost entirely displaced (by C) from the niches it had acquired in serious applications and systems programming, but retains some popularity as a hobbyist language in the MS-DOS and Macintosh worlds. See also Kamin's interpreters, p2c. ["The Programming Language Pascal", N. Wirth, Acta Informatica 1:35-63, 1971]. ["PASCAL User Manual and Report", K. Jensen & N. Wirth, Springer 1975] made significant revisions to the language. [BS 6192, "Specification for Computer Programming Language Pascal", British Standards Institute 1982].