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102-505: The PL/M programming language (an acronym of P rogramming L anguage for M icrocomputers ) is a high-level language conceived and developed by Gary Kildall in 1973 for Hank Smith at Intel for its microprocessors . The language incorporated ideas from PL/I , ALGOL and XPL , and had an integrated macro processor . As a graduate of the University of Washington Kildall had used their Burroughs B5500 computer, and as such
204-533: A basic block , to whole procedures, or even the whole program. There is a trade-off between the granularity of the optimizations and the cost of compilation. For example, peephole optimizations are fast to perform during compilation but only affect a small local fragment of the code, and can be performed independently of the context in which the code fragment appears. In contrast, interprocedural optimization requires more compilation time and memory space, but enable optimizations that are only possible by considering
306-412: A concrete syntax tree (CST, parse tree) and then transforming it into an abstract syntax tree (AST, syntax tree). In some cases additional phases are used, notably line reconstruction and preprocessing, but these are rare. The main phases of the front end include the following: The middle end, also known as optimizer, performs optimizations on the intermediate representation in order to improve
408-406: 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
510-400: 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,
612-467: A type system , variables , and mechanisms for error handling . An implementation of 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
714-422: A PDP-7 in B. Unics eventually became spelled Unix. Bell Labs started the development and expansion of C based on B and BCPL. The BCPL compiler had been transported to Multics by Bell Labs and BCPL was a preferred language at Bell Labs. Initially, a front-end program to Bell Labs' B compiler was used while a C compiler was developed. In 1971, a new PDP-11 provided the resource to define extensions to B and rewrite
816-437: A Production Quality Compiler (PQC) from formal definitions of source language and the target. PQCC tried to extend the term compiler-compiler beyond the traditional meaning as a parser generator (e.g., Yacc ) without much success. PQCC might more properly be referred to as a compiler generator. PQCC research into code generation process sought to build a truly automatic compiler-writing system. The effort discovered and designed
918-405: A compiler up into small programs is a technique used by researchers interested in producing provably correct compilers. Proving the correctness of a set of small programs often requires less effort than proving the correctness of a larger, single, equivalent program. Regardless of the exact number of phases in the compiler design, the phases can be assigned to one of three stages. The stages include
1020-432: A component of an IDE (VADS, Eclipse, Ada Pro). The interrelationship and interdependence of technologies grew. The advent of web services promoted growth of web languages and scripting languages. Scripts trace back to the early days of Command Line Interfaces (CLI) where the user could enter commands to be executed by the system. User Shell concepts developed with languages to write shell programs. Early Windows designs offered
1122-447: 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
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#17327797886561224-520: A different CPU or operating system than the one on which the cross-compiler itself runs. A bootstrap compiler is often a temporary compiler, used for compiling a more permanent or better optimised compiler for a language. Related software include decompilers , programs that translate from low-level languages to higher level ones; programs that translate between high-level languages, usually called source-to-source compilers or transpilers ; language rewriters , usually programs that translate
1326-628: A front end, a middle end, and a back end. This front/middle/back-end approach makes it possible to combine front ends for different languages with back ends for different CPUs while sharing the optimizations of the middle end. Practical examples of this approach are the GNU Compiler Collection , Clang ( LLVM -based C/C++ compiler), and the Amsterdam Compiler Kit , which have multiple front-ends, shared optimizations and multiple back-ends. The front end analyzes
1428-527: A grammar for the language, though in more complex cases these require manual modification. The lexical grammar and phrase grammar are usually context-free grammars , which simplifies analysis significantly, with context-sensitivity handled at the semantic analysis phase. The semantic analysis phase is generally more complex and written by hand, but can be partially or fully automated using attribute grammars . These phases themselves can be further broken down: lexing as scanning and evaluating, and parsing as building
1530-422: 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,
1632-432: A result, compilers were split up into smaller programs which each made a pass over the source (or some representation of it) performing some of the required analysis and translations. The ability to compile in a single pass has classically been seen as a benefit because it simplifies the job of writing a compiler and one-pass compilers generally perform compilations faster than multi-pass compilers . Thus, partly driven by
1734-431: A simple batch programming capability. The conventional transformation of these language used an interpreter. While not widely used, Bash and Batch compilers have been written. More recently sophisticated interpreted languages became part of the developers tool kit. Modern scripting languages include PHP, Python, Ruby and Lua. (Lua is widely used in game development.) All of these have interpreter and compiler support. "When
1836-399: A specified order) developed to perform well on 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
1938-598: A very efficient manner. PL/M was the first higher level programming language for microprocessor-based computers and was the original implementation language for those parts of the CP/M operating system which were not written in assembler. Many Intel and Zilog Z80 -based embedded systems were programmed in PL/M during the 1970s and 1980s. For instance, the firmware of the Service Processor component of CISC IBM AS/400
2040-608: A wide variety of uses. Many aspects of programming language design involve tradeoffs—for example, exception handling simplifies error handling, but at 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
2142-492: Is Open64 , which is used by many organizations for research and commercial purposes. Due to the extra time and space needed for compiler analysis and optimizations, some compilers skip them by default. Users have to use compilation options to explicitly tell the compiler which optimizations should be enabled. The back end is responsible for the CPU architecture specific optimizations and for code generation . The main phases of
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#17327797886562244-406: 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
2346-415: 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
2448-613: Is also commercial support, for example, AdaCore, was founded in 1994 to provide commercial software solutions for Ada. GNAT Pro includes the GNU GCC based GNAT with a tool suite to provide an integrated development environment . High-level languages continued to drive compiler research and development. Focus areas included optimization and automatic code generation. Trends in programming languages and development environments influenced compiler technology. More compilers became included in language distributions (PERL, Java Development Kit) and as
2550-419: 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
2652-469: 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
2754-446: Is favored due to its modularity and separation of concerns . Most commonly, the frontend is broken into three phases: lexical analysis (also known as lexing or scanning), syntax analysis (also known as scanning or parsing), and semantic analysis . Lexing and parsing comprise the syntactic analysis (word syntax and phrase syntax, respectively), and in simple cases, these modules (the lexer and parser) can be automatically generated from
2856-401: Is no longer supported by Intel, but aftermarket tools like PL/M-to-C source-code translators exist. 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
2958-403: 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
3060-444: 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
3162-474: 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
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3264-442: 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
3366-402: 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
3468-481: 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
3570-508: 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
3672-599: The (since 1995, object-oriented) programming language Ada . The Ada STONEMAN document formalized the program support environment (APSE) along with the kernel (KAPSE) and minimal (MAPSE). An Ada interpreter NYU/ED supported development and standardization efforts with the American National Standards Institute (ANSI) and the International Standards Organization (ISO). Initial Ada compiler development by
3774-455: 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
3876-587: The Early PL/I (EPL) compiler by Doug McIlory and Bob Morris from Bell Labs. EPL supported the project until a boot-strapping compiler for the full PL/I could be developed. Bell Labs left the Multics project in 1969, and developed a system programming language B based on BCPL concepts, written by Dennis Ritchie and Ken Thompson . Ritchie created a boot-strapping compiler for B and wrote Unics (Uniplexed Information and Computing Service) operating system for
3978-528: The Sun 3/60 Solaris targeted to Motorola 68020 in an Army CECOM evaluation. There were soon many Ada compilers available that passed the Ada Validation tests. The Free Software Foundation GNU project developed the GNU Compiler Collection (GCC) which provides a core capability to support multiple languages and targets. The Ada version GNAT is one of the most widely used Ada compilers. GNAT is free but there
4080-670: The U.S. Military Services included the compilers in a complete integrated design environment along the lines of the STONEMAN document. Army and Navy worked on the Ada Language System (ALS) project targeted to DEC/VAX architecture while the Air Force started on the Ada Integrated Environment (AIE) targeted to IBM 370 series. While the projects did not provide the desired results, they did contribute to
4182-471: The University of Cambridge was originally developed as a compiler writing tool. Several compilers have been implemented, Richards' book provides insights to the language and its compiler. BCPL was not only an influential systems programming language that is still used in research but also provided a basis for the design of B and C languages. BLISS (Basic Language for Implementation of System Software)
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4284-660: The advanced 80286 and the 32-bit 80386 . There were also PL/M compilers developed for later microcontrollers, such as the Intel 8061 and 8096 / MCS-96 architecture family (PL/M-96). While some PL/M compilers were "native", meaning that they ran on systems using that same microprocessor, e.g. for the Intel ISIS operating system, there were also cross compilers , for instance PLMX , which ran on other operating environments such as Digital Research CP/M, Microsoft 's DOS , and Digital Equipment Corporation 's VAX/VMS . PL/M
4386-435: The basis of digital modern computing development during World War II. Primitive binary languages evolved because digital devices only understand ones and zeros and the circuit patterns in the underlying machine architecture. In the late 1940s, assembly languages were created to offer a more workable abstraction of the computer architectures. Limited memory capacity of early computers led to substantial technical challenges when
4488-433: The behavior of multiple functions simultaneously. Interprocedural analysis and optimizations are common in modern commercial compilers from HP , IBM , SGI , Intel , Microsoft , and Sun Microsystems . The free software GCC was criticized for a long time for lacking powerful interprocedural optimizations, but it is changing in this respect. Another open source compiler with full analysis and optimization infrastructure
4590-487: 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
4692-591: The compiler. By 1973 the design of C language was essentially complete and the Unix kernel for a PDP-11 was rewritten in C. Steve Johnson started development of Portable C Compiler (PCC) to support retargeting of C compilers to new machines. Object-oriented programming (OOP) offered some interesting possibilities for application development and maintenance. OOP concepts go further back but were part of LISP and Simula language science. Bell Labs became interested in OOP with
4794-402: 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
4896-408: 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
4998-432: 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
5100-433: 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
5202-407: The development of C++ . C++ was first used in 1980 for systems programming. The initial design leveraged C language systems programming capabilities with Simula concepts. Object-oriented facilities were added in 1983. The Cfront program implemented a C++ front-end for C84 language compiler. In subsequent years several C++ compilers were developed as C++ popularity grew. In many application domains,
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#17327797886565304-551: The development of compiler technology: Early operating systems and software were written in assembly language. In the 1960s and early 1970s, the use of high-level languages for system programming was still controversial due to resource limitations. However, several research and industry efforts began the shift toward high-level systems programming languages, for example, BCPL , BLISS , B , and C . BCPL (Basic Combined Programming Language) designed in 1966 by Martin Richards at
5406-424: The development of high-level languages followed naturally from the capabilities offered by digital computers. High-level languages are formal languages that are strictly defined by their syntax and semantics which form the high-level language architecture. Elements of these formal languages include: The sentences in a language may be defined by a set of rules called a grammar. Backus–Naur form (BNF) describes
5508-424: The early days, the approach taken to compiler design was directly affected by the complexity of the computer language to be processed, the experience of the person(s) designing it, and the resources available. Resource limitations led to the need to pass through the source code more than once. A compiler for a relatively simple language written by one person might be a single, monolithic piece of software. However, as
5610-491: The field of compiling began in the late 50s, its focus was limited to the translation of high-level language programs into machine code ... The compiler field is increasingly intertwined with other disciplines including computer architecture, programming languages, formal methods, software engineering, and computer security." The "Compiler Research: The Next 50 Years" article noted the importance of object-oriented languages and Java. Security and parallel computing were cited among
5712-464: The first (algorithmic) programming language for computers called Plankalkül ("Plan Calculus"). Zuse also envisioned a Planfertigungsgerät ("Plan assembly device") to automatically translate the mathematical formulation of a program into machine-readable punched film stock . While no actual implementation occurred until the 1970s, it presented concepts later seen in APL designed by Ken Iverson in
5814-423: The first compilers were designed. Therefore, the compilation process needed to be divided into several small programs. The front end programs produce the analysis products used by the back end programs to generate target code. As computer technology provided more resources, compiler designs could align better with the compilation process. It is usually more productive for a programmer to use a high-level language, so
5916-559: The first pass needs to gather information about declarations appearing after statements that they affect, with the actual translation happening during a subsequent pass. The disadvantage of compiling in a single pass is that it is not possible to perform many of the sophisticated optimizations needed to generate high quality code. It can be difficult to count exactly how many passes an optimizing compiler makes. For instance, different phases of optimization may analyse one expression many times but only analyse another expression once. Splitting
6018-461: 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
6120-933: The form of expressions without a change of language; and compiler-compilers , compilers that produce compilers (or parts of them), often in a generic and reusable way so as to be able to produce many differing compilers. A compiler is likely to perform some or all of the following operations, often called phases: preprocessing , lexical analysis , parsing , semantic analysis ( syntax-directed translation ), conversion of input programs to an intermediate representation , code optimization and machine specific code generation . Compilers generally implement these phases as modular components, promoting efficient design and correctness of transformations of source input to target output. Program faults caused by incorrect compiler behavior can be very difficult to track down and work around; therefore, compiler implementers invest significant effort to ensure compiler correctness . Compilers are not
6222-454: The future research targets. A compiler implements a formal transformation from a high-level source program to a low-level target program. Compiler design can define an end-to-end solution or tackle a defined subset that interfaces with other compilation tools e.g. preprocessors, assemblers, linkers. Design requirements include rigorously defined interfaces both internally between compiler components and externally between supporting toolsets. In
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#17327797886566324-421: The idea of using a higher-level language quickly caught on. Because of the expanding functionality supported by newer programming languages and the increasing complexity of computer architectures, compilers became more complex. DARPA (Defense Advanced Research Projects Agency) sponsored a compiler project with Wulf's CMU research team in 1970. The Production Quality Compiler-Compiler PQCC design would produce
6426-621: The idea. Compiler In computing , a compiler is a computer program that translates computer code written in one programming language (the source language) into another language (the target language). The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a low-level programming language (e.g. assembly language , object code , or machine code ) to create an executable program. There are many different types of compilers which produce output in different useful forms. A cross-compiler produces code for
6528-402: 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
6630-429: 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
6732-417: 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,
6834-434: The late 1950s. APL is a language for mathematical computations. Between 1949 and 1951, Heinz Rutishauser proposed Superplan , a high-level language and automatic translator. His ideas were later refined by Friedrich L. Bauer and Klaus Samelson . High-level language design during the formative years of digital computing provided useful programming tools for a variety of applications: Compiler technology evolved from
6936-511: 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
7038-400: 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
7140-408: The need for a strictly defined transformation of the high-level source program into a low-level target program for the digital computer. The compiler could be viewed as a front end to deal with the analysis of the source code and a back end to synthesize the analysis into the target code. Optimization between the front end and back end could produce more efficient target code. Some early milestones in
7242-639: 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
7344-570: The only language processor used to transform source programs. An interpreter is computer software that transforms and then executes the indicated operations. The translation process influences the design of computer languages, which leads to a preference of compilation or interpretation. In theory, a programming language can have both a compiler and an interpreter. In practice, programming languages tend to be associated with just one (a compiler or an interpreter). Theoretical computing concepts developed by scientists, mathematicians, and engineers formed
7446-455: 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
7548-436: 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
7650-436: 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
7752-483: 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
7854-667: The overall effort on Ada development. Other Ada compiler efforts got underway in Britain at the University of York and in Germany at the University of Karlsruhe. In the U. S., Verdix (later acquired by Rational) delivered the Verdix Ada Development System (VADS) to the Army. VADS provided a set of development tools including a compiler. Unix/VADS could be hosted on a variety of Unix platforms such as DEC Ultrix and
7956-442: 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
8058-511: The performance and the quality of the produced machine code. The middle end contains those optimizations that are independent of the CPU architecture being targeted. The main phases of the middle end include the following: Compiler analysis is the prerequisite for any compiler optimization, and they tightly work together. For example, dependence analysis is crucial for loop transformation . The scope of compiler analysis and optimizations vary greatly; their scope may range from operating within
8160-646: The phase structure of the PQC. The BLISS-11 compiler provided the initial structure. The phases included analyses (front end), intermediate translation to virtual machine (middle end), and translation to the target (back end). TCOL was developed for the PQCC research to handle language specific constructs in the intermediate representation. Variations of TCOL supported various languages. The PQCC project investigated techniques of automated compiler construction. The design concepts proved useful in optimizing compilers and compilers for
8262-585: 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
8364-489: 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
8466-417: 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
8568-420: 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
8670-429: The resource limitations of early systems, many early languages were specifically designed so that they could be compiled in a single pass (e.g., Pascal ). In some cases, the design of a language feature may require a compiler to perform more than one pass over the source. For instance, consider a declaration appearing on line 20 of the source which affects the translation of a statement appearing on line 10. In this case,
8772-404: 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
8874-686: 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
8976-490: The source code to build an internal representation of the program, called the intermediate representation (IR). It also manages the symbol table , a data structure mapping each symbol in the source code to associated information such as location, type and scope. While the frontend can be a single monolithic function or program, as in a scannerless parser , it was traditionally implemented and analyzed as several phases, which may execute sequentially or concurrently. This method
9078-469: The source language grows in complexity the design may be split into a number of interdependent phases. Separate phases provide design improvements that focus development on the functions in the compilation process. Classifying compilers by number of passes has its background in the hardware resource limitations of computers. Compiling involves performing much work and early computers did not have enough memory to contain one program that did all of this work. As
9180-440: The syntax of "sentences" of a language. It was developed by John Backus and used for the syntax of Algol 60 . The ideas derive from the context-free grammar concepts by linguist Noam Chomsky . "BNF and its extensions have become standard tools for describing the syntax of programming notations. In many cases, parts of compilers are generated automatically from a BNF description." Between 1942 and 1945, Konrad Zuse designed
9282-525: 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
9384-401: 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
9486-424: 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,
9588-475: 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
9690-476: 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
9792-419: Was aware of the potential of high-level languages such as ESPOL for systems programming. Unlike other contemporary languages such as Pascal or BASIC , PL/M had no standard input or output routines. It included features targeted at the low-level hardware specific to the target microprocessors, and as such, it could support direct access to any location in memory, I/O ports and the processor interrupt flags in
9894-432: Was developed for a Digital Equipment Corporation (DEC) PDP-10 computer by W. A. Wulf's Carnegie Mellon University (CMU) research team. The CMU team went on to develop BLISS-11 compiler one year later in 1970. Multics (Multiplexed Information and Computing Service), a time-sharing operating system project, involved MIT , Bell Labs , General Electric (later Honeywell ) and was led by Fernando Corbató from MIT. Multics
9996-407: 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
10098-550: 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
10200-430: 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
10302-539: Was written in PL/M. The original PL/M compiler targeted the Intel 8008 . An updated version (PL/M-80) generated code for the 8080 processor, which would also run on the newer Intel 8085 as well as on the Zilog Z80 family (as it is backward-compatible with the 8080). Later followed compilers for the Intel 8048 and Intel 8051 -microcontroller family (PL/M-51) as well as for the 8086 (8088) (PL/M-86), 80186 (80188) and subsequent 8086-based processors, including
10404-470: Was written in the PL/I language developed by IBM and IBM User Group. IBM's goal was to satisfy business, scientific, and systems programming requirements. There were other languages that could have been considered but PL/I offered the most complete solution even though it had not been implemented. For the first few years of the Multics project, a subset of the language could be compiled to assembly language with
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