Ada (programming language): Difference between revisions

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| operating system = Multi- or [[cross-platform]]

| file ext = .adb, .ads

| website = {{urlURL|https://www.adaic.org/|adaic.org}}

| wikibooks = Ada Programming

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[[File:Ada Mascot with slogan.svg|thumb|Ada mascot with slogan]]

'''Ada''' is a [[structured programming|structured]], [[statically typed]], [[Imperative programming|imperative]], and [[Object-oriented programming|object-oriented]] [[high-level programming language]], inspired by [[Pascal (programming language)|Pascal]] and other languages. It has built-in language support for ''[[design by contract]]'' (DbC), extremely [[Strong and weak typing|strong typing]], explicit concurrency, tasks, synchronous [[message passing]], protected [[Object (computer science)|objects]], and [[nondeterministic programming|non-determinism]]. Ada improves code safety and maintainability by using the [[compiler]] to find errors in favor of [[Runtime (program lifecycle phase)|runtime]] errors. Ada is an [[International standard|international]] [[technical standard]], jointly defined by the [[International Organization for Standardization]] (ISO), and the [[International Electrotechnical Commission]] (IEC). {{As of|May 2023}}, the standard, ISO/IEC 8652:2023, is called Ada 2022 informally.<ref name="ada-letters-june2023">{{cite journal |last1=Pinho |first1=Luis Miguel |title=From the Editor's Desk |journal=Ada Letters |volume=XLIII |number=1 |publisher=Association for Computing Machinery |date=June 2023 |page=3 |doi=10.1145/3631483 |doi-broken-date=1 November 2024 |url=https://dl.acm.org/action/showFmPdf?doi=10.1145%2F3631483}}</ref>

'''Ada''' is a [[structured programming|structured]], [[statically typed]], [[Imperative programming|imperative]], and [[Object-oriented programming|object-oriented]] [[high-level programming language]], inspired by [[Pascal (programming language)|Pascal]] and other languages. It has built-in language support for ''[[design by contract]]'' (DbC), extremely [[Strong and weak typing|strong typing]], explicit concurrency, tasks, synchronous [[message passing]], protected [[Object (computer science)|objects]], and [[nondeterministic programming|non-determinism]]. Ada improves code safety and maintainability by using the [[compiler]] to find errors in favor of [[Runtime (program lifecycle phase)|runtime]] errors. Ada is an [[International standard|international]] [[technical standard]], jointly defined by the [[International Organization for Standardization]] (ISO), and the [[International Electrotechnical Commission]] (IEC). {{As of|May 2023}}, the standard, ISO/IEC 8652:2023, is called Ada 2022 informally.<ref name="ada-letters-june2023">{{cite journal |last1=Pinho |first1=Luis Miguel |title=From the Editor's Desk |journal=Ada Letters |volume=XLIII |number=1 |publisher=Association for Computing Machinery |date=June 2023 |page=3 |doi=10.1145/3631483 |doi-broken-date=1 NovemberJuly 20242025 |url=https://dl.acm.org/action/showFmPdf?doi=10.1145%2F3631483}}</ref>

Ada was originally designed by a team led by French [[computer scientist]] [[Jean Ichbiah]] of [[Groupe Bull|Honeywell]] under contract to the [[United States Department of Defense]] (DoD) from 1977 to 1983 to supersede over 450 programming languages then used by the DoD.<ref>{{cite web|title=The Ada Programming Language|url=http://groups.engin.umd.umich.edu/CIS/course.des/cis400/ada/ada.html|website=University of Mich|access-date=27 May 2016|archive-url=https://web.archive.org/web/20160522063844/http://groups.engin.umd.umich.edu/CIS/course.des/cis400/ada/ada.html|archive-date=2016-05-22}}</ref> Ada was named after [[Ada Lovelace]] (1815–1852), who has been credited as the first computer programmer.<ref>{{cite journal|doi=10.1109/MAHC.2003.1253887|title=Lovelace & Babbage and the creation of the 1843 'notes'|journal=IEEE Annals of the History of Computing|volume=25|issue=4|pages=16–26|year=2003|last1=Fuegi|first1=J|last2=Francis|first2=J|s2cid=40077111}}</ref>

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Features of Ada include: [[Strong and weak typing|strong typing]], [[modular programming]] mechanisms ([[Modular programming|packages]]), [[run-time checking]], [[Parallel computing|parallel processing]] ([[Task (computing)|tasks]], synchronous [[message passing]], protected objects, and nondeterministic [[Switch statement|select statements]]), [[exception handling]], and [[generic programming|generics]]. Ada&nbsp;95 added support for [[object-oriented programming]], including [[dynamic dispatch]].

The [[Syntax (programming languages)|syntax]] of Ada minimizes choices of ways to perform basic operations, and prefers English keywords (such as "{{code|or else"}} and "{{code|and then"}}) to symbols (such as "{{code||"{{!}}{{!}}}} and "{{code|&&"}}). Ada uses the basic arithmetical operators "{{code|+"}}, "{{code|-"}}, "{{code|*"}}, and "{{code|/"}}, but avoids using other symbols. Code blocks are delimited by words such as "'declare"', "'begin"', and "'end"', where the "'end"' (in most cases) is followed by the identifierkeyword of the block that it closes (e.g., ''{{code|if}} ... {{code|end if''}}, ''{{code|loop}} ... {{code|end loop''}}). In the case of conditional blocks this avoids a ''[[dangling else]]'' that could pair with the wrong nested 'if'-expression in other languages likesuch as C or Java.

Ada is designed for developing very large software systems. Ada packages can be compiled separately. Ada package specifications (the package interface) can also be compiled separately without the implementation to check for consistency. This makes it possible to detect problems early during the design phase, before implementation starts.

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Though the semantics of the language allow automatic [[garbage collection (computer science)|garbage collection]] of inaccessible objects, most implementations do not support it by default, as it would cause unpredictable behaviour in real-time systems. Ada supports a limited form of [[region-based memory management]], and in Ada, destroying a storage pool also destroys all the objects in the pool.

A double-[[dash]] ("{{code|--"}}), resembling an [[em dash]], denotes comment text. Comments stop at end of line; there is intentionally no way to make a comment span multiple lines, to prevent unclosed comments from accidentally voiding whole sections of source code. Disabling a whole block of code therefore requires the prefixing of each line (or column) individually with "{{code|--"}}. While this clearly denotes disabled code by creating a column of repeated "'--"' down the page, it also renders the experimental dis/re-enablement of large blocks a more drawn-out process in editors without block commenting support.

The semicolon ("{{code|;"}}) is a [[statement terminator]], and the null or no-operation statement is <{{code>|null;</code>}}. A single <{{code>|;</code>}} without a statement to terminate is not allowed.

Unlike most [[International Organization for Standardization|ISO]] standards, the Ada language definition (known as the ''Ada Reference Manual'' or ''ARM'', or sometimes the ''Language Reference Manual'' or ''LRM'') is [[free content]]. Thus, it is a common reference for Ada programmers, not only programmers implementing Ada compilers. Apart from the reference manual, there is also an extensive rationale document which explains the language design and the use of various language constructs. This document is also widely used by programmers. When the language was revised, a new rationale document was written.

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HOLWG crafted the '''<span class="anchor" id="Steelman language requirements">Steelman language requirements</span>''' , a series of documents stating the requirements they felt a programming language should satisfy. Many existing languages were formally reviewed, but the team concluded in 1977 that no existing language met the specifications. The requirements were created by the [[United States Department of Defense]] in ''The Department of Defense Common High Order Language program'' in 1978. The predecessors of this document were called, in order, "Strawman", "Woodenman", "Tinman" and "Ironman".<ref>Department of Defense (June 1978), [https://web.archive.org/web/20200914235620/https://dwheeler.com/steelman/steelman.htm Requirements for High Order Computer Programming Languages: "Steelman"]</ref> The requirements focused on the needs of [[embedded systems|embedded]] computer applications, and emphasised reliability, maintainability, and efficiency. Notably, they included [[exception handling]] facilities, [[run-time checking]], and [[parallel computing]].

It was concluded that no existing language met these criteria to a sufficient extent,<ref>SoftTech Inc. (1976), [[iarchive:DTIC_ADA037637DTIC ADA037637/mode/2up|"Evaluation of ALGOL 68, Jovial J3B, Pascal, Simula 67, and TACPOL Versus TINMAN - Requirements for a Common High Order Programming Language."]] - See also: [[ALGOL 68]], [[JOVIAL]] J3B, [[Pascal (programming language)|Pascal]], [[Simula]] 67, and TACPOL (Defense Technical Information Center - DTIC ADA037637, Report Number 1021-14)</ref> so a contest was called to create a language that would be closer to fulfilling them. The design that won this contest became the Ada programming language. The resulting language followed the Steelman requirements closely, though not exactly.

[[File:Ada Lovelace portrait.jpg|thumb|225x225px|Watercolour painting of Ada Lovelace]]

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The first validated Ada implementation was the NYU Ada/Ed translator,<ref>{{cite web |url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA136759 |title=Ada Compiler Validation Summary Report: NYU Ada/ED, Version 19.7 V-001 |author=SofTech Inc. |place=Waltham, MA |date=1983-04-11 |access-date=2010-12-16 |archive-url=https://web.archive.org/web/20120312080046/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA136759 |archive-date=2012-03-12 }}</ref> certified on April 11, 1983. NYU Ada/Ed is implemented in the high-level set language [[SETL]].<ref>{{cite book |last1=Dewar |first1=Robert B. K. |last2=Fisher |first2=Gerald A. Jr. |last3=Schonberg |first3=Edmond |last4=Froelich |first4=Robert |last5=Bryant |first5=Stephen |last6=Goss |first6=Clinton F. |last7=Burke |first7=Michael |title=Proceeding of the ACM-SIGPLAN symposium on Ada programming language – SIGPLAN '80 |chapter=The NYU Ada translator and interpreter |volume=15 |issue=11 |pages=194–201 |date=November 1980 |isbn=0-89791-030-3 |doi=10.1145/948632.948659|s2cid=10586359}}</ref> Several commercial companies began offering Ada compilers and associated development tools, including [[Alsys]], [[TeleSoft]], [[DDC-I]], [[Advanced Computer Techniques]], [[Tartan Laboratories]], [[Irvine Compiler]], [[TLD Systems]], and [[Verdix]].<ref name="adaic-1992">{{cite news |title=Ada Validated Compilers List |publisher=Ada Information Clearinghouse |date=July 1, 1992 |pages=1–36}}</ref> Computer manufacturers who had a significant business in the defense, aerospace, or related industries, also offered Ada compilers and tools on their platforms; these included [[Concurrent Computer Corporation]], [[Cray Research, Inc.]], [[Digital Equipment Corporation]], [[Harris Computer Systems]], and [[Siemens Nixdorf Informationssysteme AG]].<ref name="adaic-1992" />

In 1991, the US Department of Defense began to require the use of Ada (the ''Ada mandate'') for all software,<ref>{{cite web|url=http://archive.adaic.com/pol-hist/policy/mandate.txt |title=The Congressional Ada Mandate |author=Ada Information Clearinghouse |date=1994 |access-date=2015-06-07 |archive-url=https://web.archive.org/web/20160304073005/http://archive.adaic.com/pol-hist/policy/mandate.txt |archive-date=2016-03-04}}</ref> though exceptions to this rule were often granted.<ref name="sward" /> The Department of Defense Ada mandate was effectively removed in 1997, as the DoD began to embrace [[commercial off-the-shelf]] (COTS) technology.<ref name="sward">{{cite conference |contribution=The rise, fall and persistence of Ada |first=Ricky E. |last=Sward |date=November 2010 |title=SIGAda '10: Proceedings of the ACM SIGAda annual international conference on SIGAda |pages=71–74 |url=http://dl.acm.org/citation.cfm?id=1879063.1879081&coll=DL&dl=GUIDE&CFID=551420221&CFTOKEN=60383966 | doi=10.1145/1879063.1879081|isbn=978-1-4503-0027-8|url-access=subscription }}</ref> Similar requirements existed in other [[North Atlantic Treaty Organization|NATO]] countries: Ada was required for NATO systems involving [[command and control]] and other functions, and Ada was the mandated or preferred language for defense-related applications in countries such as Sweden, Germany, and Canada.<ref>{{cite book |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a217657.pdf |archive-url=https://web.archive.org/web/20191215065214/http://www.dtic.mil/dtic/tr/fulltext/u2/a217657.pdf |url-status=live |archive-date=December 15, 2019 |first=Nicholas J. |last=Babiak |title=Ada, the New DoD Weapon System Computer Language – Panacea or Calamity |publisher=[[Air University (United States Air Force)]] |date=1989 |pages=39–40}}</ref>

By the late 1980s and early 1990s, Ada compilers had improved in performance, but there were still barriers to fully exploiting Ada's abilities, including a tasking model that was different from what most real-time programmers were used to.<ref name="SIGAda-Rosen" />

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| 1983

| Ada 83/87

| ANSI MIL-STD 1815A,<br />ISO/IEC 8652:1987

|-

| 1995

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Preliminary Ada can be found in ACM Sigplan Notices Vol 14, No 6, June 1979<ref>{{cite web|url=https://dl.acm.org/doi/pdf/10.1145/956650.956651 |title=ACM Sigplan Notices |volume=14 |number= 6 |date=June 1979|pages=1–145 |doi=10.1145/956650.956651 |last1=Ichbiah |first1=J. D.}}</ref>

Ada was first published in 1980 as an [[American National Standards Institute|ANSI]] standard ANSI/'''MIL-STD 1815'''. As this very first version held many errors and inconsistencies ,{{Efn|see Summary of Ada Language Changes<ref>[https://dl.acm.org/doi/pdf/10.1145/989791.989792 Summary of Ada Language Changes]</ref>}} the revised edition was published in 1983 as ANSI/MIL-STD 1815A. Without any further changes, it became an ISO standard in 1987.<ref>{{Cite web |last= |date=2013-02-21 |title=ISO 8652:1987 |url=https://www.iso.org/standard/16028.html |access-date=2024-01-19 |website=ISO |language=en}}</ref> This version of the language is commonly known as '''Ada&nbsp;83''', from the date of its adoption by ANSI, but is sometimes referred to also as '''Ada&nbsp;87''', from the date of its adoption by ISO.<ref>{{Cite web |title=Ada 83 LRM, Front Page |url=http://archive.adaic.com/standards/83lrm/html/Welcome.html |access-date=2024-01-19 |website=archive.adaic.com}}</ref> There is also a French translation; DIN translated it into German as DIN 66268 in 1988.

'''Ada&nbsp;95''', the joint ISO/IEC/ANSI standard ISO/IEC 8652:1995<ref>{{Cite web |last= |title=ISO/IEC 8652:1995 |url=https://www.iso.org/standard/22983.html |access-date=2024-01-19 |website=ISO |language=en}}</ref><ref>{{Cite web |title=Ada 95 Language Reference Manual (original) – Ada Resource Association |url=https://www.adaic.org/ada-resources/standards/ada-95-documents/lrm-original/ |access-date=2024-01-19 |website=www.adaic.org}}</ref> was published in February 1995, making it the first ISO standard object-oriented programming language. To help with the standard revision and future acceptance, the [[US Air Force]] funded the development of the [[GNAT]] [[Compiler]]. Presently, the GNAT Compiler is part of the [[GNU Compiler Collection]].

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Work has continued on improving and updating the technical content of the Ada language. A Technical Corrigendum to Ada&nbsp;95 was published in October 2001,<ref>[https://www.iso.org/standard/35451.html ISO/IEC 8652:1995/Corr 1:2001]</ref><ref>[http://www.adaic.org/standards/95lrm/html/RM-TTL.html Ada 95 RM with TC 1]</ref> and a major Amendment, ISO/IEC 8652:1995/Amd 1:2007 <ref>{{Cite web |last= |title=ISO/IEC 8652:1995/Amd 1:2007 |url=https://www.iso.org/standard/45001.html |access-date=2024-01-19 |website=ISO |language=en}}</ref><ref>{{Cite web |title=Ada Reference Manual, ISO/IEC 8652:2007(E) Ed. 3 |url=https://www.adaic.org/resources/add_content/standards/05rm/html/RM-TTL.html |access-date=2024-01-19 |website=www.adaic.org}}</ref> was published on March 9, 2007, commonly known as '''Ada&nbsp;2005''' because work on the new standard was finished that year.

At the Ada-Europe 2012 conference in Stockholm, the Ada Resource Association (ARA) and Ada-Europe announced the completion of the design of the latest version of the Ada language and the submission of the reference manual to the [[ISO/IEC JTC 1/SC 22]]/WG 9 of the [[International Organization for Standardization]] (ISO) and the [[International Electrotechnical Commission]] (IEC) for approval. ISO/IEC 8652:2012<ref>{{Cite web |last= |date=2013-03-28 |title=ISO/IEC 8652:2012 |url=https://www.iso.org/standard/61507.html |access-date=2024-01-19 |website=ISO |language=en}}</ref> (see [https://www.adaic.org/resources/add_content/standards/12rm/html/RM-TTL.html Ada 2012 RM]) was published in December 2012, known as '''Ada&nbsp;2012'''. A technical corrigendum, ISO/IEC 8652:2012/COR 1:2016, was published <ref>{{Cite web |last= |title=ISO/IEC 8652:2012/Cor 1:2016 |url=https://www.iso.org/standard/69798.html |access-date=2024-01-19 |website=ISO |language=en}}</ref> (see [http://www.ada-auth.org/standards/rm12_w_tc1/html/RM-TTL.html RM 2012 with TC 1]).

On May 2, 2023, the Ada community saw the formal approval of publication of the '''Ada&nbsp;2022''' edition of the programming language standard.<ref name="ada-letters-june2023" />

Despite the names Ada 83, 95 etc., legally there is only one Ada standard, the one of the last ISO/IEC standard: with the acceptance of a new standard version, the previous one becomes withdrawn. The other names are just informal ones referencing a certain edition.

Other related standards include [[Graphical Kernel System|ISO/IEC 8651]]-3:1988 ''Information processing systems—Computer graphics—Graphical Kernel System (GKS) language bindings—Part 3: Ada''.

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{{Portal|Computer programming}}

* [[List of compilers#Ada compilers|Ada compilers]]

* [[{{annotated link|ALGOL 68]]}}

* {{annotated link|APSE}}

* [[APSE]] – a specification for a programming environment to support software development in Ada

* [[{{annotated link|Pascal (programming language)|Pascal]]}}

* {{annotated link|Ravenscar profile}}

* [[Ravenscar profile]] – a subset of the Ada tasking features designed for safety-critical hard real-time computing

* [[{{annotated link|Smalltalk]]}}

* {{annotated link|SPARK (programming language)|SPARK}}

* [[SPARK (programming language)|SPARK]] – a programming language consisting of a highly restricted subset of Ada, annotated with meta-information describing desired component behavior and individual runtime requirements

* {{annotated link|VHDL}}

* [[VHDL]], Ada-based hardware description language

==Notes==

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===== {{No more links}} ===== -->

{{Commons category|Ada (programming language)}}

{{Wikibooks|Ada Programming}}

{{Wikisourcecat|Ada|Steelman language requirements}}

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[[Category:.NET programming languages]]

[[Category:Avionics programming languages]]

[[Category:High-integrity Integrityprogramming Programming Languagelanguages]]

[[Category:Multi-paradigm programming languages]]

[[Category:Programming language standards]]