programming language (redirected from (programming) language)

programming language, syntax, grammar, and symbols or words used to give instructions to a computer.

Development of Low-Level Languages

All computers operate by following machine language programs, a long sequence of instructions called machine code that is addressed to the hardware of the computer and is written in binary notation (see numeration), which uses only the digits 1 and 0. First-generation languages, called machine languages, required the writing of long strings of binary numbers to represent such operations as "add," "subtract," "and compare." Later improvements allowed octal, decimal, or hexadecimal representation of the binary strings.

Because writing programs in machine language is impractical (it is tedious and error prone), symbolic, or assembly, languages—second-generation languages—were introduced in the early 1950s. They use simple mnemonics such as A for "add" or M for "multiply," which are translated into machine language by a computer program called an assembler. The assembler then turns that program into a machine language program. An extension of such a language is the macro instruction, a mnemonic (such as "READ") for which the assembler substitutes a series of simpler mnemonics. The resulting machine language programs, however, are specific to one type of computer and will usually not run on a computer with a different type of central processing unit (CPU).

Evolution of High-Level Languages

The lack of portability between different computers led to the development of high-level languages—so called because they permitted a programmer to ignore many low-level details of the computer's hardware. Further, it was recognized that the closer the syntax, rules, and mnemonics of the programming language could be to "natural language" the less likely it became that the programmer would inadvertently introduce errors (called "bugs") into the program. Hence, in the mid-1950s a third generation of languages came into use. These algorithmic, or procedural, languages are designed for solving a particular type of problem. Unlike machine or symbolic languages, they vary little between computers. They must be translated into machine code by a program called a compiler or interpreter.

Early computers were used almost exclusively by scientists, and the first high-level language, Fortran [Formula translation], was developed (1953–57) for scientific and engineering applications by John Backus at the IBM Corp. A program that handled recursive algorithms better, LISP [LISt Processing], was developed by John McCarthy at the Massachusetts Institute of Technology in the early 1950s; implemented in 1959, it has become the standard language for the artificial intelligence community. COBOL [COmmon Business Oriented Language], the first language intended for commercial applications, is still widely used; it was developed by a committee of computer manufacturers and users under the leadership of Grace Hopper, a U.S. Navy programmer, in 1959. ALGOL [ALGOrithmic Language], developed in Europe about 1958, is used primarily in mathematics and science, as is APL [A Programming Language], published in the United States in 1962 by Kenneth Iverson. PL/1 [Programming Language 1], developed in the late 1960s by the IBM Corp., and ADA [for Ada Augusta, countess of Lovelace, biographer of Charles Babbage], developed in 1981 by the U.S. Dept. of Defense, are designed for both business and scientific use.

BASIC [Beginner's All-purpose Symbolic Instruction Code] was developed by two Dartmouth College professors, John Kemeny and Thomas Kurtz, as a teaching tool for undergraduates (1966); it subsequently became the primary language of the personal computer revolution. In 1971, Swiss professor Nicholas Wirth developed a more structured language for teaching that he named Pascal (for French mathematician Blaise Pascal, who built the first successful mechanical calculator). Modula 2, a Pascallike language for commercial and mathematical applications, was introduced by Wirth in 1982. Ten years before that, to implement the UNIX operating system, Dennis Ritchie of Bell Laboratories produced a language that he called C; along with its extensions, called C++, developed by Bjarne Stroustrup of Bell Laboratories, it has perhaps become the most widely used general-purpose language among professional programmers because of its ability to deal with the rigors of object-oriented programming. Java is an object-oriented language similar to C++ but simplified to eliminate features that are prone to programming errors. Java was developed specifically as a network-oriented language, for writing programs that can be safely downloaded through the Internet and immediately run without fear of computer viruses. Using small Java programs called applets, World Wide Web pages can be developed that include a full range of multimedia functions.

Fourth-generation languages are nonprocedural—they specify what is to be accomplished without describing how. The first one, FORTH, developed in 1970 by American astronomer Charles Moore, is used in scientific and industrial control applications. Most fourth-generation languages are written for specific purposes. Fifth-generation languages, which are still in their infancy, are an outgrowth of artificial intelligence research. PROLOG [PROgramming LOGic], developed by French computer scientist Alain Colmerauer and logician Philippe Roussel in the early 1970s, is useful for programming logical processes and making deductions automatically.

Many other languages have been designed to meet specialized needs. GPSS [General Purpose System Simulator] is used for modeling physical and environmental events, and SNOBOL [String-Oriented Symbolic Language] is designed for pattern matching and list processing. LOGO, a version of LISP, was developed in the 1960s to help children learn about computers. PILOT [Programmed Instruction Learning, Or Testing] is used in writing instructional software, and Occam is a nonsequential language that optimizes the execution of a program's instructions in parallel-processing systems.

There are also procedural languages that operate solely within a larger program to customize it to a user's particular needs. These include the programming languages of several database and statistical programs, the scripting languages of communications programs, and the macro languages of word-processing programs.

Compilers and Interpreters

Once the program is written and has had any errors repaired (a process called debugging), it may be executed in one of two ways, depending on the language. With some languages, such as C or Pascal, the program is turned into a separate machine language program by a compiler, which functions much as an assembler does. Other languages, such as LISP, do not have compilers but use an interpreter to read and interpret the program a line at a time and convert it into machine code. A few languages, such as BASIC, have both compilers and interpreters. Source code, the form in which a program is written in a high-level language, can easily be transferred from one type of computer to another, and a compiler or interpreter specific to the machine configuration can convert the source code to object, or machine, code.

Bibliography

See R. Cezzar, A Guide to Programming Languages: Overview and Comparison (1995), T. W. Pratt and M. V. Zelkowitz, Programming Languages: Design and Implementation (3d ed. 1996); C. Ghezzi and M. Jazayem, Programming Language Concepts (3d ed. 1997); R. W. Sebasta, Concepts of Programming Languages (4th ed. 1998).

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programming language

Language in which a computer programmer writes instructions for a computer to execute. Some languages, such as COBOL, FORTRAN, Pascal, and C, are known as procedural languages because they use a sequence of commands to specify how the machine is to solve a problem. Others, such as LISP, are functional, in that programming is done by invoking procedures (sections of code executed within a program). Languages that support object-oriented programming take the data to be manipulated as their point of departure. Programming languages can also be classified as high-level or low-level. Low-level languages address the computer in a way that it can understand directly, but they are very far from human language. High-level languages deal in concepts that humans devise and can understand, but they must be translated by means of a compiler into language the computer understands.

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programming language

A language used to write instructions for the computer. It lets the programmer express data processing in a symbolic manner without regard to machine-specific details.

From Source Code to Machine Language
The statements that are written by the programmer are called "source language," and they are translated into the computer's "machine language" by programs called "assemblers," "compilers" and "interpreters." For example, when a programmer writes MULTIPLY HOURS TIMES RATE, the verb MULTIPLY must be turned into a code that means multiply, and the nouns HOURS and RATE must be turned into memory locations where those items of data are actually located.

Grammar and Syntax
Like human languages, each programming language has its own grammar and syntax. There are many dialects of the same language, and each dialect requires its own translation system. Standards have been set by ANSI for many programming languages, and ANSI-standard languages are dialect free. However, it can take years for new features to be included in ANSI standards, and new dialects inevitably spring up as a result.

Low Level and High Level
Programming languages fall into two categories: low-level assembly languages and high-level languages. Assembly languages are available for each CPU family, and each assembly instruction is translated into one machine instruction by the assembler program. With high-level languages, a programming statement may be translated into one or several machine instructions by the compiler.

Following is a brief summary of the major high-level languages. Look up each one for more details. For a list of high-level programming languages designed for client/server development, see client/server development system.

ActionScript
Programming language for Flash programs. See Flash and ActionScript.

Ada
Comprehensive, Pascal-based language used by the Department of Defense. See Ada.

ALGOL
International language for expressing algorithms. See ALGOL.

APL
Used for statistics and mathematical matrices. Requires special keyboard symbols. See APL.

BASIC
Developed as a timesharing language in the 1960s. It has been widely used in microcomputer programming in the past, and various dialects of BASIC have been incorporated into many different applications. Microsoft's Visual Basic is widely used. See BASIC and Visual Basic.

C
Developed in the 1980s at AT&T. Widely used to develop commercial applications. Unix is written in C. See C.

C++
Object-oriented version of C that is popular because it combines object-oriented capability with traditional C programming syntax. See C++.

C#
Pronounced "C-sharp." A Microsoft .NET language based on C++ with elements from Visual Basic and Java. See .NET.

COBOL
Developed in the 1960s. Widely used for mini and mainframe programming. See COBOL.

dBASE
Used to be widely used in business applications, but FoxPro (Microsoft's dBASE) has survived the longest. See Visual FoxPro, FoxBase, Clipper and Quicksilver.

F#
Pronounced "F-sharp." A Microsoft .NET scripting language based on ML. See F#.

FORTH
Developed in the 1960s, FORTH has been used in process control and game applications. See FORTH.

FORTRAN
Developed in 1954 by IBM, it was the first major scientific programming language and continues to be widely used. Some commercial applications have been developed in FORTRAN. See FORTRAN.

Java
The programming language developed by Sun and repositioned for Web use. It is widely used on the server side, although client applications are increasingly used. See Java.

JavaScript
A scripting language widely used on the Web. JavaScript is embedded into many HTML pages. See JavaScript.

LISP
Developed in 1960. Used for AI applications. Its syntax is very different than other languages. See LISP.

Logo
Developed in the 1960s, it was noted for its ease of use and "turtle graphics" drawing functions. See Logo.

M
Originally MUMPS (Massachusetts Utility MultiProgramming System), it includes its own database. It is widely used in medical applications. See M.

Modula-2
Enhanced version of Pascal introduced in 1979. See Modula-2.

Pascal
Originally an academic language developed in the 1970s. Borland commercialized it with its Turbo Pascal. See Pascal.

Perl
A scripting language widely used on the Web to write CGI scripts. See Perl.

Prolog
Developed in France in 1973. Used throughout Europe and Japan for AI applications. See Prolog.

Python
A scripting language used for system utilities and Internet scripts. Developed in Amsterdam by Guido van Rossum. See Python.

REXX
Runs on IBM mainframes and OS/2. Used as a general purpose macro language. See REXX.

VBScript
Subset of Visual Basic used on the Web similar to JavaScript. See VBScript.

Visual Basic
Version of BASIC for Windows programming from Microsoft that has been widely used. See Visual Basic.

Web Languages
Languages such as JavaScript, Jscript, Perl and CGI are used to automate Web pages as well as link them to other applications running in servers.

Millions of Languages!
Programmers must use standard names for the instruction verbs (add, compare, etc.) in the language they use. In addition, a company generally uses standardized names for the data elements in its databases. However, programmers typically "make up" names for all the functions (subroutines) in the program. Since programmers are loathe to document their code, the readability of the names chosen for these routines is critical.

In a single program, the programmer could make up hundreds of function names as well as names for data structures that hold fixed sums, predefined tables and display messages.

Just Make It Up!
Unless rigid naming conventions are enforced or pair programming is used, whereby one person looks over the shoulders of the other, programmers can make up names that make no sense whatsoever. Little understood by non-programmers, this is the bane of many professionals when they have to modify someone else's program. Debugging another person's code is very difficult if the names are cryptic, and there are few comments, which is often the case. It often requires tracing the logic one statement at a time.

In fact, if programmers are not attentive to naming things clearly, they can have a miserable time reading their own code later on. See pair programming, programmer, to the recruiter and naming fiascos.

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programming language

a simple language system designed to facilitate the writing of computer programs

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programming language [′prō‚gram·iŋ ‚laŋ·gwij]

(computer science)

The language used by a programmer to write a program for a computer.

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(language)

programming language - A formal language in which computer programs are written. The definition of a particular language consists of both syntax (how the various symbols of the language may be combined) and semantics (the meaning of the language constructs). Languages are classified as low level if they are close to machine code and high level if each language statement corresponds to many machine code instructions (though this could also apply to a low level language with extensive use of macros, in which case it would be debatable whether it still counted as low level). A roughly parallel classification is the description as first generation language through to fifth generation language. The other major classification of languages distinguishes between imperative languages, procedural language and declarative languages. Programming languages time-line/family tree.