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{{Short description|Programming language that abstracts details of computing hardware}}
{{Use dmy dates|date=May 2023}}
{{Use American English|date=January 2019}}
A '''high-level programming language''' is a [[programming language]] with strong [[Abstraction (computer science)|abstraction]] from the details of the [[computer]]. In contrast to [[low-level programming language]]s, it may use [[natural language]] ''elements'', be easier to use, or may automate (or even hide entirely) significant areas of computing systems (e.g. [[memory management]]), making the process of developing a program simpler and more understandable than when using a lower-level language. The amount of abstraction provided defines how "high-level" a programming language is.<ref>{{cite web |archive-url=https://web.archive.org/web/20070826224349/http://www.ittc.ku.edu/hybridthreads/glossary/index.php |archive-date=2007-08-26 |url=http://www.ittc.ku.edu/hybridthreads/glossary/index.php |url-status=dead |title=HThreads - RD Glossary<!-- Bot generated title -->}}</ref>
''High-level'' refers to a level of abstraction from the hardware details of a [[CPU |processor]] inherent in [[machine code |machine]] and [[assembly language| assembly]] code. Rather than dealing with registers, memory addresses, and call stacks, high-level languages deal with variables, arrays, [[object (computer science)|object]]s, arithmetic and [[Boolean expression]]s, [[function (computing)|functions]], loops, [[Thread (computer science)|thread]]s, locks, and other computer science abstractions, intended to facilitate [[Correctness (computer science)|correctness]] and [[software maintenance |maintainability]]. Unlike low-level [[assembly language]]s, high-level languages have few, if any, language elements that translate directly to a machine's native [[opcode]]s. Other features, such as string handling, [[Object-oriented programming]] features, and file input/output, may also be provided. A high-level language allows for source code that is detached and separated from the machine details. That is, unlike low-level languages like assembly and machine code, high-level language code may result in data movements without the programmer's knowledge. Some control of what instructions to execute is handed to the compiler.
==History==
In the 1960s, a high-level programming language using a [[compiler]] was commonly called an ''[[autocode]]''.<ref name=kleith>{{cite book|last=London|first=Keith|year=1968|title=Introduction to Computers|publisher=Faber and Faber Limited|___location=24 Russell Square London WC1|isbn=0571085938|page=184|chapter=4, Programming|quote=The 'high' level programming languages are often called autocodes and the processor program, a compiler.}}<!--The book has no ISBN number, instead it has an SBN number. There is no typo in the prior sentence.--></ref>
Examples of autocodes are [[COBOL]] and [[Fortran]].<ref name=kleith2>{{cite book|last=London|first=Keith|title=Introduction to Computers|year=1968|publisher=Faber and Faber Limited|___location=24 Russell Square London WC1|isbn=0571085938|page=186|chapter=4, Programming|quote=Two high level programming languages which can be used here as examples to illustrate the structure and purpose of autocodes are COBOL (Common Business Oriented Language) and FORTRAN (Formular Translation).}}<!--The book has no ISBN number, instead it has an SBN number. There is no typo in the prior sentence.--></ref>
The first high-level programming language designed for computers was [[Plankalkül]], created by [[Konrad Zuse]].<ref>{{ill|Wolfgang Giloi{{!}}Giloi, Wolfgang, K.|de|Wolfgang Giloi}} (1997). "Konrad Zuse's Plankalkül: The First High-Level "non von Neumann" Programming Language". IEEE Annals of the History of Computing, vol. 19, no. 2, pp. 17–24, April–June, 1997. [http://doi.ieeecomputersociety.org/10.1109/85.586068 (abstract)]</ref> However, it was not implemented in his time, and his original contributions were largely isolated from other developments due to [[World War II]], aside from the language's influence on the "Superplan" language by [[Heinz Rutishauser]] and also to some degree [[ALGOL]]. The first significantly widespread high-level language was [[Fortran]], a machine-independent development of IBM's earlier [[Autocode]] systems. The [[ALGOL]] family, with [[ALGOL 58]] defined in 1958 and [[ALGOL 60]] defined in 1960 by committees of European and American computer scientists, introduced [[recursion]] as well as [[nested functions]] under [[lexical scope]]. ALGOL 60 was also the first language with a clear distinction between [[call by value|value]] and [[call by name|name-parameter]]s and their corresponding [[Semantics (computer science)|semantics]].<ref>Although it lacked a notion of [[call by reference|reference-parameter]]s, which could be a problem in some situations. Several successors, including [[ALGOL W]], [[ALGOL 68]], [[Simula]], [[Pascal (programming language)|Pascal]], [[Modula]] and [[Ada (programming language)|Ada]] thus included reference-parameters (The related C-language family instead allowed addresses as <code>value</code>-parameters).</ref> ALGOL also introduced several [[structured programming]] concepts, such as the <code>while-do</code> and <code>if-then-else</code> constructs and its [[Syntax (programming languages)|syntax]] was the first to be described in formal notation – ''[[Backus–Naur form]]'' (BNF). During roughly the same period, [[COBOL]] introduced [[Record (computer science)|record]]s (also called structs) and [[Lisp (programming language)|Lisp]] introduced a fully general [[lambda abstraction]] in a programming language for the first time.
==Abstraction penalty==
A high-level language provides features that standardize common tasks, permit rich debugging, and maintain architectural agnosticism. On the other hand, a low-level language requires the coder to work at a lower-level of abstraction which is generally more challenging, but does allow for [[program optimization |optimizations]] that are not possible with a high-level language. This ''abstraction penalty'' for using a high-level language instead of a low-level language is real, but in practice, low-level optimizations rarely improve performance at the [[user experience]] level.<ref>{{cite journal
|author=Surana P
|title=Meta-Compilation of Language Abstractions.
|year=2006
|url=http://lispnyc.org/meeting-assets/2007-02-13_pinku/SuranaThesis.pdf
|access-date=2008-03-17
|url-status=live
|archive-url=https://web.archive.org/web/20150217154926/http://lispnyc.org/meeting-assets/2007-02-13_pinku/SuranaThesis.pdf
|archive-date=2015-02-17
}}</ref><ref>{{cite web
| first = Argyn
| last = Kuketayev
| website = Application Development Trends
| title = The Data Abstraction Penalty (DAP) Benchmark for Small Objects in Java.
| url = http://www.adtmag.com/joop/article.aspx?id=4597
| access-date = 2008-03-17
| archive-url = https://web.archive.org/web/20090111091710/http://www.adtmag.com/joop/article.aspx?id=4597
| archive-date = 2009-01-11
| url-status = dead
}}</ref><ref>{{Cite book
| last1 = Chatzigeorgiou
| last2 = Stephanides
| editor-last = Blieberger
| editor2-last = Strohmeier
| contribution = Evaluating Performance and Power Of Object-Oriented Vs. Procedural Programming Languages
| title = Proceedings - 7th International Conference on Reliable Software Technologies - Ada-Europe'2002
| year = 2002
| pages = 367
| publisher = Springer
}}</ref> None the less, code that needs to run quickly and efficiently may require the use of a lower-level language, even if a higher-level language would make the coding easier to write and maintain. In many cases, critical portions of a program mostly in a high-level language are coded in assembly in order to meet tight timing or memory constraints. A well-designed compiler for a high-level language can produce code comparable in efficiency to what could be coded by hand in assembly, and the higher-level abstractions sometimes allow for optimizations that beat the performance of hand-coded assembly.<ref>
{{Cite journal
|author1=Manuel Carro |author2=José F. Morales |author3=Henk L. Muller |author4=G. Puebla |author5=M. Hermenegildo | journal = Proceedings of the 2006 International Conference on Compilers, Architecture and Synthesis for Embedded Systems
| title = High-level languages for small devices: a case study
| url = http://www.clip.dia.fi.upm.es/papers/carro06:stream_interpreter_cases.pdf
| year = 2006
| publisher = ACM
}}</ref> Since a high-level language is designed independent of a specific computing [[Computer architecture |system architecture]], a program written in such a language can run on any computing context with a compatible compiler or interpreter.
Unlike a low-level language that is inherently tied to processor hardware, a high-level language can be improved, and new high-level languages can evolve from others with the goal of aggregating the most popular constructs with improved features. For example, [[Scala (programming language)|Scala]] maintains backward compatibility with [[Java (programming language)|Java]]. Code written in Java continue to be usable even if a developer switches to Scala. This makes the transition easier and extends the lifespan of a [[codebase]]. In contrast, low-level programs rarely survive beyond the [[Computer architecture |system architecture]] which they were written for.
== Relative meaning ==
{{refimprove section|date=October 2018}}
The terms ''high-level'' and ''low-level'' are inherently relative, and languages can be compared as higher or lower level to each other. Sometimes the [[C (programming language)|C language]] is considered as either high-level or low-level depending on one's perspective. Regardless, most agree that C is higher level than assembly and lower level than most other languages.
C supports constructs such as expression evaluation, [[parameter |parameterized]] and recursive functions, data types and structures which are generally not supported in assembly or directly by a processor but C does provide lower-level features such as auto-increment and pointer math. But C lacks many higher-level abstracts common in other languages such as [[garbage collection]] and a built-in string type. In the introduction of [[The C Programming Language]] (second edition) by [[Brian Kernighan]] and [[Dennis Ritchie]], C is described as "not a very high level" language.<ref>{{cite book|last1=Kernighan|first1=Brian W.|last2=Ritchie|first2=Dennis M.|date=1988|title=The C Programming Language: 2nd Edition|url=https://books.google.com/books?id=FGkPBQAAQBAJ|url-status=bot: unknown|publisher=Prentice Hall|isbn=9780131103627|archive-url=https://web.archive.org/web/20221025180501/https://books.google.com/books?id=FGkPBQAAQBAJ|archive-date=25 October 2022|access-date=25 October 2022}}</ref>
Assembly language is higher-level than machine code, but still highly tied to the processor hardware. But, assembly may provide some higher-level features such as [[Macro (computer science)|macro]]s, relatively limited expressions, constants, variables, procedures, and [[data structure]]s.
[[Machine code]] is at a slightly higher level abstraction than the [[microcode]] or [[micro-operation]]s used internally in many processors.<ref>{{Cite book|title=The art of assembly language|last=Hyde, Randall.|date=2010|publisher=No Starch Press|isbn=9781593273019|edition= 2nd|___location=San Francisco|oclc=635507601|url=https://books.google.com/books?id=sYHtTvQ-ObIC}}</ref>
== Execution modes ==
{{refimprove section|find=Execution modes|date=October 2018}}
The source code of a high-level language may be processed in various ways, including
; Compiled: A [[compiler]] transforms source code into other code. Sometimes, and traditionally, a compiler generates native machine code that is interpreted by the processor. But, today many execution models involve generating an [[intermediate representation]] (i.e. [[bytecode]]) that is later interpreted in software or converted to native code at runtime (via [[JIT compilation]]).
; [[Transpiled]]: Code may be translated into source code of another language (typically lower-level) for which a compiler or interpreter is available. [[JavaScript]] and the [[C (programming language)|C]] are common targets for such translators. For example, C and C++ code can be seen as generated from Eiffel code when using the [[EiffelStudio]] IDE. In Eiffel, the ''translated'' process is referred to as ''transcompiling'' or ''transcompiled'', and the Eiffel compiler as a transcompiler or [[source-to-source compiler]].
; Software interpreted: A [[interpreter (software)|software interpreter]] performs the actions encoded in source code without generating native machine code.
; Hardware interpreted: Although uncommon, a processor with a [[high-level language computer architecture]] can process a high-level language without a compilation step. For example, the [[Burroughs large systems]] were target machines for [[ALGOL 60]].<ref>{{Citation|last=Chu|first=Yaohan|chapter=Concepts of High-Level Language Computer Architecture|date=1975|pages=1–14|publisher=Elsevier|isbn=9780121741501|doi=10.1016/b978-0-12-174150-1.50007-0|title=High-Level Language Computer Architecture}}</ref>
Note that a language is not strictly interpreted or compiled. Rather, an execution model involves a compiler or an interpreter and the same language might be used with different execution models. For example, [[ALGOL 60]] and [[Fortran]] have both been interpreted even though they were more typically compiled. Similarly, Java shows the difficulty of trying to apply these labels to languages, rather than to implementations. Java is compiled to bytecode which is then executed by either interpreting in a [[Java virtual machine]] (JVM) or JIT compiled.
== See also ==
{{Portal|Computer programming}}
* [[Generational list of programming languages]]
* [[Categorical list of programming languages]]
* [[Very high-level programming language]]s
* [[Low-level programming language]]s
* [[High-level assembler]]
* [[Abstraction (computer science)]]
{{Clear}}
== References ==
{{Reflist}}
== External links ==
* http://c2.com/cgi/wiki?HighLevelLanguage - The [[WikiWikiWeb]]'s article on high-level programming languages
{{Types of programming languages}}
{{Authority control}}
{{DEFAULTSORT:High-Level Programming Language}}
[[Category:High-level programming languages| ]]
[[Category:Programming language classification]]
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