This is an accepted version of this page
74-547: CORAL , short for Computer On-line Real-time Applications Language is a programming language originally developed in 1964 at the Royal Radar Establishment (RRE), Malvern, Worcestershire , in the United Kingdom. The R was originally for "radar", not "real-time". It was influenced primarily by JOVIAL , and thus ALGOL , but is not a subset of either. The most widely-known version, CORAL 66 ,
148-406: A heap and automatic garbage collection . For the next decades, Lisp dominated artificial intelligence applications. In 1978, another functional language, ML , introduced inferred types and polymorphic parameters . After ALGOL (ALGOrithmic Language) was released in 1958 and 1960, it became the standard in computing literature for describing algorithms . Although its commercial success
222-400: A logic called a type system . Other forms of static analyses like data flow analysis may also be part of static semantics. Programming languages such as Java and C# have definite assignment analysis , a form of data flow analysis, as part of their respective static semantics. Once data has been specified, the machine must be instructed to perform operations on the data. For example,
296-588: A CORAL compiler approved by IECCA, and thus allowing a compiler to be marketed as a CORAL 66 compiler, the candidate compiler had to compile and execute a standard suite of 25 test programs and 6 benchmark programs. The process was part of the British Standard (BS) 5905 approval process. This methodology was observed and adapted later by the United States Department of Defense for the certification of Ada compilers. Source code for
370-660: A Coral 66 compiler (written in BCPL ) has been recovered and the Official Definition of Coral 66 document by Her Majesty's Stationery Office (HMSO) has been scanned; the Ministry of Defence patent office has issued a licence to the Edinburgh Computer History project to allow them to put both the code and the language reference online for non-commercial use. A variant of Coral 66 named PO-CORAL
444-444: A PAS has all the functionality of a British Standard for the purposes of creating schemes such as management systems and product benchmarks as well as codes of practice. A PAS is a living document and after two years the document will be reviewed and a decision made with the client as to whether or not this should be taken forward to become a formal standard. The term PAS was originally an abbreviation for "product approval specification",
518-447: A data type whose elements, in many languages, must consist of a single type of fixed length. Other languages define arrays as references to data stored elsewhere and support elements of varying types. Depending on the programming language, sequences of multiple characters, called strings , may be supported as arrays of characters or their own primitive type . Strings may be of fixed or variable length, which enables greater flexibility at
592-403: A field of standardization such as ICT, quality, agriculture, manufacturing, or fire). Each sector board, in turn, constitutes several technical committees. It is the technical committees that, formally, approve a British Standard, which is then presented to the secretary of the supervisory sector board for endorsement of the fact that the technical committee has indeed completed a task for which it
666-422: A meaning to a grammatically correct sentence or the sentence may be false: The following C language fragment is syntactically correct, but performs operations that are not semantically defined (the operation *p >> 4 has no meaning for a value having a complex type and p->im is not defined because the value of p is the null pointer ): If the type declaration on the first line were omitted,
740-480: A name which was subsequently changed to "publicly available specification". However, according to BSI, not all PAS documents are structured as specifications and the term is now sufficiently well established not to require any further amplification. Copies of British Standards are sold at the BSI Online Shop or can be accessed via subscription to British Standards Online (BSOL). They can also be ordered via
814-454: A performance cost. Programming language theory is the subfield of computer science that studies the design, implementation, analysis, characterization, and classification of programming languages. Programming languages differ from natural languages in that natural languages are used for interaction between people, while programming languages are designed to allow humans to communicate instructions to machines. The term computer language
SECTION 10
#1732780998120888-425: A programming language is required in order to execute programs, namely an interpreter or a compiler . An interpreter directly executes the source code, while a compiler produces an executable program. Computer architecture has strongly influenced the design of programming languages, with the most common type ( imperative languages —which implement operations in a specified order) developed to perform well on
962-449: A prohibition on recursion to remove the need for a stack . Programming language A programming language is a system of notation for writing computer programs . Programming languages are described in terms of their syntax (form) and semantics (meaning), usually defined by a formal language . Languages usually provide features such as a type system , variables , and mechanisms for error handling . An implementation of
1036-446: A series of Publicly Available Specification (PAS) documents. PAS documents are a flexible and rapid standards development model open to all organizations. A PAS is a sponsored piece of work allowing organizations flexibility in the rapid creation of a standard while also allowing for a greater degree of control over the document's development. A typical development time frame for a PAS is around six to nine months. Once published by BSI,
1110-488: A shorthand way of claiming that certain specifications are met, while encouraging manufacturers to adhere to a common method for such a specification. The Kitemark can be used to indicate certification by BSI, but only where a Kitemark scheme has been set up around a particular standard. It is mainly applicable to safety and quality management standards. There is a common misunderstanding that Kitemarks are necessary to prove compliance with any BS standard, but in general, it
1184-406: Is a set of allowable values and operations that can be performed on these values. Each programming language's type system defines which data types exist, the type of an expression , and how type equivalence and type compatibility function in the language. According to type theory , a language is fully typed if the specification of every operation defines types of data to which the operation
1258-415: Is allowed, the fewer type errors can be detected. Early programming languages often supported only built-in, numeric types such as the integer (signed and unsigned) and floating point (to support operations on real numbers that are not integers). Most programming languages support multiple sizes of floats (often called float and double ) and integers depending on the size and precision required by
1332-419: Is applicable. In contrast, an untyped language, such as most assembly languages , allows any operation to be performed on any data, generally sequences of bits of various lengths. In practice, while few languages are fully typed, most offer a degree of typing. Because different types (such as integers and floats ) represent values differently, unexpected results will occur if one type is used when another
1406-471: Is designed for real-time computing and embedded system applications, and for use on computers with limited processing power, including those limited to fixed-point arithmetic and those without support for dynamic storage allocation. The language was an inter-service standard for British military programming, and was also widely adopted for civil purposes in the British control and automation industry. It
1480-469: Is expected. Type checking will flag this error, usually at compile time (runtime type checking is more costly). With strong typing , type errors can always be detected unless variables are explicitly cast to a different type. Weak typing occurs when languages allow implicit casting—for example, to enable operations between variables of different types without the programmer making an explicit type conversion. The more cases in which this type coercion
1554-459: Is neither desirable nor possible that every standard be 'policed' in this way. Following the move on harmonization of the standard in Europe, some British Standards are gradually being superseded or replaced by the relevant European Standards (EN). Standards are continuously reviewed and developed and are periodically allocated one or more of the following status keywords. BSI also publishes
SECTION 20
#17327809981201628-403: Is often used to specify the execution semantics of languages commonly used in practice. A significant amount of academic research goes into formal semantics of programming languages , which allows execution semantics to be specified in a formal manner. Results from this field of research have seen limited application to programming language design and implementation outside academia. A data type
1702-444: Is sometimes used interchangeably with "programming language". However, usage of these terms varies among authors. In one usage, programming languages are described as a subset of computer languages. Similarly, the term "computer language" may be used in contrast to the term "programming language" to describe languages used in computing but not considered programming languages – for example, markup languages . Some authors restrict
1776-474: Is stored. The simplest user-defined type is an ordinal type whose values can be mapped onto the set of positive integers. Since the mid-1980s, most programming languages also support abstract data types , in which the representation of the data and operations are hidden from the user , who can only access an interface . The benefits of data abstraction can include increased reliability, reduced complexity, less potential for name collision , and allowing
1850-442: Is the potential for errors to go undetected. Complete type inference has traditionally been associated with functional languages such as Haskell and ML . With dynamic typing, the type is not attached to the variable but only the value encoded in it. A single variable can be reused for a value of a different type. Although this provides more flexibility to the programmer, it is at the cost of lower reliability and less ability for
1924-402: Is used (in languages that require such declarations) or that the labels on the arms of a case statement are distinct. Many important restrictions of this type, like checking that identifiers are used in the appropriate context (e.g. not adding an integer to a function name), or that subroutine calls have the appropriate number and type of arguments, can be enforced by defining them as rules in
1998-481: Is usually defined using a combination of regular expressions (for lexical structure) and Backus–Naur form (for grammatical structure). Below is a simple grammar, based on Lisp : This grammar specifies the following: The following are examples of well-formed token sequences in this grammar: 12345 , () and (a b c232 (1)) . Not all syntactically correct programs are semantically correct. Many syntactically correct programs are nonetheless ill-formed, per
2072-557: The CPU that performs instructions on data is separate, and data must be piped back and forth to the CPU. The central elements in these languages are variables, assignment , and iteration , which is more efficient than recursion on these machines. Many programming languages have been designed from scratch, altered to meet new needs, and combined with other languages. Many have eventually fallen into disuse. The birth of programming languages in
2146-699: The Ministry of Defence ." As Coral was aimed at a variety of real-time work, rather than general office data processing, there was no standardised equivalent to a stdio library . IECCA recommended a primitive input/output (I/O) package to accompany any compiler (in a document titled Input/Output of Character data in Coral 66 Utility Programs ). Most implementers avoided this by producing Coral interfaces to extant Fortran and, later, C libraries. CORAL's most significant contribution to computing may have been enforcing quality control in commercial compilers . To have
2220-455: The 1950s was stimulated by the desire to make a universal programming language suitable for all machines and uses, avoiding the need to write code for different computers. By the early 1960s, the idea of a universal language was rejected due to the differing requirements of the variety of purposes for which code was written. Desirable qualities of programming languages include readability, writability, and reliability. These features can reduce
2294-487: The code is reached; this is called finalization. There is a tradeoff between increased ability to handle exceptions and reduced performance. For example, even though array index errors are common C does not check them for performance reasons. Although programmers can write code to catch user-defined exceptions, this can clutter a program. Standard libraries in some languages, such as C, use their return values to indicate an exception. Some languages and their compilers have
CORAL - Misplaced Pages Continue
2368-412: The collection while students can copy/paste and print but not download a standard. Up to 10% of the content of a standard can be copy/pasted for personal or internal use and up to 5% of the collection made available as a paper or electronic reference collection at the subscribing university. Because of their reference material status standards are not available for interlibrary loan. Public library users in
2442-402: The cost of increased storage space and more complexity. Other data types that may be supported include lists , associative (unordered) arrays accessed via keys, records in which data is mapped to names in an ordered structure, and tuples —similar to records but without names for data fields. Pointers store memory addresses, typically referencing locations on the heap where other data
2516-408: The cost of readability. Natural-language programming has been proposed as a way to eliminate the need for a specialized language for programming. However, this goal remains distant and its benefits are open to debate. Edsger W. Dijkstra took the position that the use of a formal language is essential to prevent the introduction of meaningless constructs. Alan Perlis was similarly dismissive of
2590-432: The cost of training programmers in a language, the amount of time needed to write and maintain programs in the language, the cost of compiling the code, and increase runtime performance. Programming language design often involves tradeoffs. For example, features to improve reliability typically come at the cost of performance. Increased expressivity due to a large number of operators makes writing code easier but comes at
2664-433: The details of the hardware, instead being designed to express algorithms that could be understood more easily by humans. For example, arithmetic expressions could now be written in symbolic notation and later translated into machine code that the hardware could execute. In 1957, Fortran (FORmula TRANslation) was invented. Often considered the first compiled high-level programming language, Fortran has remained in use into
2738-637: The first email from a head of state from the Royal Signals and Radar Establishment over the ARPANET on March 26, 1976. The message read "This message to all ARPANET users announces the availability on ARPANET of the Coral 66 compiler provided by the GEC 4080 computer at the Royal Signals and Radar Establishment, Malvern, England, ... Coral 66 is the standard real-time high level language adopted by
2812-461: The first programming languages. The earliest computers were programmed in first-generation programming languages (1GLs), machine language (simple instructions that could be directly executed by the processor). This code was very difficult to debug and was not portable between different computer systems. In order to improve the ease of programming, assembly languages (or second-generation programming languages —2GLs) were invented, diverging from
2886-626: The general adoption of British Standards and schedules in connection therewith and from time to time to revise, alter and amend such standards and schedules as experience and circumstances require. Formally, as stated in a 2002 memorandum of understanding between the BSI and the United Kingdom Government , British Standards are defined as: "British Standards" means formal consensus standards as set out in BS 0-1 paragraph 3.2 and based upon
2960-557: The idea. British Standard British Standards ( BS ) are the standards produced by the BSI Group which is incorporated under a royal charter and which is formally designated as the national standards body (NSB) for the UK. The BSI Group produces British Standards under the authority of the charter, which lays down as one of the BSI's objectives to: Set up standards of quality for goods and services, and prepare and promote
3034-402: The invention of the microprocessor , computers in the 1970s became dramatically cheaper. New computers also allowed more user interaction, which was supported by newer programming languages. Lisp , implemented in 1958, was the first functional programming language. Unlike Fortran, it supported recursion and conditional expressions , and it also introduced dynamic memory management on
CORAL - Misplaced Pages Continue
3108-429: The language's rules; and may (depending on the language specification and the soundness of the implementation) result in an error on translation or execution. In some cases, such programs may exhibit undefined behavior . Even when a program is well-defined within a language, it may still have a meaning that is not intended by the person who wrote it. Using natural language as an example, it may not be possible to assign
3182-417: The languages intended for execution. He also argues that textual and even graphical input formats that affect the behavior of a computer are programming languages, despite the fact they are commonly not Turing-complete, and remarks that ignorance of programming language concepts is the reason for many flaws in input formats. The first programmable computers were invented at the end of the 1940s, and with them,
3256-511: The machine language to make programs easier to understand for humans, although they did not increase portability. Initially, hardware resources were scarce and expensive, while human resources were cheaper. Therefore, cumbersome languages that were time-consuming to use, but were closer to the hardware for higher efficiency were favored. The introduction of high-level programming languages ( third-generation programming languages —3GLs)—revolutionized programming. These languages abstracted away
3330-400: The meaning of languages, as opposed to their form ( syntax ). Static semantics defines restrictions on the structure of valid texts that are hard or impossible to express in standard syntactic formalisms. For compiled languages, static semantics essentially include those semantic rules that can be checked at compile time. Examples include checking that every identifier is declared before it
3404-639: The new programming languages uses static typing while a few numbers of new languages use dynamic typing like Ring and Julia . Some of the new programming languages are classified as visual programming languages like Scratch , LabVIEW and PWCT . Also, some of these languages mix between textual and visual programming usage like Ballerina . Also, this trend lead to developing projects that help in developing new VPLs like Blockly by Google . Many game engines like Unreal and Unity added support for visual scripting too. Every programming language includes fundamental elements for describing data and
3478-455: The operations or transformations applied to them, such as adding two numbers or selecting an item from a collection. These elements are governed by syntactic and semantic rules that define their structure and meaning, respectively. A programming language's surface form is known as its syntax . Most programming languages are purely textual; they use sequences of text including words, numbers, and punctuation, much like written natural languages. On
3552-436: The option of turning on and off error handling capability, either temporarily or permanently. One of the most important influences on programming language design has been computer architecture . Imperative languages , the most commonly used type, were designed to perform well on von Neumann architecture , the most common computer architecture. In von Neumann architecture, the memory stores both data and instructions, while
3626-436: The order of execution of key instructions via the use of semaphores , controlling access to shared data via monitor , or enabling message passing between threads. Many programming languages include exception handlers, a section of code triggered by runtime errors that can deal with them in two main ways: Some programming languages support dedicating a block of code to run regardless of whether an exception occurs before
3700-483: The other hand, some programming languages are graphical , using visual relationships between symbols to specify a program. The syntax of a language describes the possible combinations of symbols that form a syntactically correct program. The meaning given to a combination of symbols is handled by semantics (either formal or hard-coded in a reference implementation ). Since most languages are textual, this article discusses textual syntax. The programming language syntax
3774-442: The parsing phase. Languages that have constructs that allow the programmer to alter the behavior of the parser make syntax analysis an undecidable problem , and generally blur the distinction between parsing and execution. In contrast to Lisp's macro system and Perl's BEGIN blocks, which may contain general computations, C macros are merely string replacements and do not require code execution. The term semantics refers to
SECTION 50
#17327809981203848-505: The popular von Neumann architecture . While early programming languages were closely tied to the hardware , over time they have developed more abstraction to hide implementation details for greater simplicity. Thousands of programming languages—often classified as imperative, functional , logic , or object-oriented —have been developed for a wide variety of uses. Many aspects of programming language design involve tradeoffs—for example, exception handling simplifies error handling, but at
3922-673: The principles of standardisation recognised inter alia in European standardisation policy. Products and services which BSI certifies as having met the requirements of specific standards within designated schemes are awarded the Kitemark . BSI Group began in 1901 as the Engineering Standards Committee , led by James Mansergh , to standardize the number and type of steel sections, in order to make British manufacturers more efficient and competitive. Over time
3996-585: The program would trigger an error on the undefined variable p during compilation. However, the program would still be syntactically correct since type declarations provide only semantic information. The grammar needed to specify a programming language can be classified by its position in the Chomsky hierarchy . The syntax of most programming languages can be specified using a Type-2 grammar, i.e., they are context-free grammars . Some languages, including Perl and Lisp, contain constructs that allow execution during
4070-489: The programmer specifies a desired result and allows the interpreter to decide how to achieve it. During the 1980s, the invention of the personal computer transformed the roles for which programming languages were used. New languages introduced in the 1980s included C++, a superset of C that can compile C programs but also supports classes and inheritance . Ada and other new languages introduced support for concurrency . The Japanese government invested heavily into
4144-417: The programmer. Storing an integer in a type that is too small to represent it leads to integer overflow . The most common way of representing negative numbers with signed types is twos complement , although ones complement is also used. Other common types include Boolean —which is either true or false—and character —traditionally one byte , sufficient to represent all ASCII characters. Arrays are
4218-420: The programming language to check for errors. Some languages allow variables of a union type to which any type of value can be assigned, in an exception to their usual static typing rules. In computing, multiple instructions can be executed simultaneously. Many programming languages support instruction-level and subprogram-level concurrency. By the twenty-first century, additional processing power on computers
4292-450: The publishing units of many other national standards bodies ( ANSI , DIN , etc.) and from several specialized suppliers of technical specifications. British Standards, including European and international adoptions, are available in many university and public libraries that subscribe to the BSOL platform. Librarians and lecturers at UK-based subscribing universities have full access rights to
4366-404: The semantics may define the strategy by which expressions are evaluated to values, or the manner in which control structures conditionally execute statements . The dynamic semantics (also known as execution semantics ) of a language defines how and when the various constructs of a language should produce a program behavior. There are many ways of defining execution semantics. Natural language
4440-686: The so-called fifth-generation languages that added support for concurrency to logic programming constructs, but these languages were outperformed by other concurrency-supporting languages. Due to the rapid growth of the Internet and the World Wide Web in the 1990s, new programming languages were introduced to support Web pages and networking . Java , based on C++ and designed for increased portability across systems and security, enjoyed large-scale success because these features are essential for many Internet applications. Another development
4514-425: The standards developed to cover many aspects of tangible engineering, and then engineering methodologies including quality systems, safety and security. The BSI Group as a whole does not produce British Standards, as standards work within the BSI is decentralized. The governing board of BSI establishes a Standards Board. The Standards Board does little apart from setting up sector boards (a sector in BSI parlance being
SECTION 60
#17327809981204588-525: The term "programming language" to Turing complete languages. Most practical programming languages are Turing complete, and as such are equivalent in what programs they can compute. Another usage regards programming languages as theoretical constructs for programming abstract machines and computer languages as the subset thereof that runs on physical computers, which have finite hardware resources. John C. Reynolds emphasizes that formal specification languages are just as much programming languages as are
4662-401: The twenty-first century. Around 1960, the first mainframes —general purpose computers—were developed, although they could only be operated by professionals and the cost was extreme. The data and instructions were input by punch cards , meaning that no input could be added while the program was running. The languages developed at this time therefore are designed for minimal interaction. After
4736-424: The twenty-first century. C allows access to lower-level machine operations more than other contemporary languages. Its power and efficiency, generated in part with flexible pointer operations, comes at the cost of making it more difficult to write correct code. Prolog , designed in 1972, was the first logic programming language, communicating with a computer using formal logic notation. With logic programming,
4810-475: The underlying data structure to be changed without the client needing to alter its code. In static typing , all expressions have their types determined before a program executes, typically at compile-time. Most widely used, statically typed programming languages require the types of variables to be specified explicitly. In some languages, types are implicit; one form of this is when the compiler can infer types based on context. The downside of implicit typing
4884-476: Was service-oriented programming , designed to exploit distributed systems whose components are connected by a network. Services are similar to objects in object-oriented programming, but run on a separate process. C# and F# cross-pollinated ideas between imperative and functional programming. After 2010, several new languages— Rust , Go , Swift , Zig and Carbon —competed for the performance-critical software for which C had historically been used. Most of
4958-525: Was constituted. The standards produced are titled British Standard XXXX[-P]:YYYY where XXXX is the number of the standard, P is the number of the part of the standard (where the standard is split into multiple parts) and YYYY is the year in which the standard came into effect. BSI Group currently has over 27,000 active standards. Products are commonly specified as meeting a particular British Standard, and in general, this can be done without any certification or independent testing. The standard simply provides
5032-642: Was developed during the late 1970s to early 1980s by the British General Post Office (GPO), together with GEC , STC and Plessey , for use on the System X digital telephone exchange control computers. This was later renamed BT-CORAL when British Telecom was spun off from the Post Office. Unique features of this language were the focus on real-time execution, message processing, limits on statement execution between waiting for input, and
5106-407: Was increasingly coming from the use of additional processors, which requires programmers to design software that makes use of multiple processors simultaneously to achieve improved performance. Interpreted languages such as Python and Ruby do not support the concurrent use of multiple processors. Other programming languages do support managing data shared between different threads by controlling
5180-713: Was introduced to ensure CORAL compilers met the specifications. This process was later adopted by the US Department of Defense while defining Ada . Coral 66 is a general-purpose programming language based on ALGOL 60 , with some features from Coral 64, JOVIAL , and Fortran . It includes structured record types (as in Pascal ) and supports the packing of data into limited storage (also as in Pascal). Like Edinburgh IMP it allows inline (embedded) assembly language , and also offers good runtime checking and diagnostics. It
5254-550: Was limited, most popular imperative languages—including C , Pascal , Ada , C++ , Java , and C# —are directly or indirectly descended from ALGOL 60. Among its innovations adopted by later programming languages included greater portability and the first use of context-free , BNF grammar. Simula , the first language to support object-oriented programming (including subtypes , dynamic dispatch , and inheritance ), also descends from ALGOL and achieved commercial success. C, another ALGOL descendant, has sustained popularity into
5328-489: Was subsequently developed by I. F. Currie and M. Griffiths under the auspices of the Inter-Establishment Committee for Computer Applications (IECCA). Its official definition, edited by Woodward , Wetherall, and Gorman, was first published in 1970. In 1971, CORAL was selected by the Ministry of Defence as the language for future military applications and to support this, a standardization program
5402-430: Was that of dynamically typed scripting languages — Python , JavaScript , PHP , and Ruby —designed to quickly produce small programs that coordinate existing applications . Due to their integration with HTML , they have also been used for building web pages hosted on servers . During the 2000s, there was a slowdown in the development of new programming languages that achieved widespread popularity. One innovation
5476-667: Was used to write software for both the Ferranti and General Electric Company (GEC) computers from 1971 onwards. Implementations also exist for the Interdata 8/32, PDP-11 , VAX and Alpha platforms and HPE Integrity Servers ; for the Honeywell , and for the Computer Technology Limited (CTL, later ITL) Modular-1 ; and for SPARC running Solaris , and Intel running Linux . Queen Elizabeth II sent
#119880