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| developer =
| typing = [[Static typing|static]], [[Strong and weak typing|strong]], [[Type safety|safe]], [[Nominal type system|nominal]]
| implementations = AdaCore [[GNAT]],<ref>{{Cite web|url=https://www.adacore.com/download|title=Commercial software solutions for Ada, C and C++|website=AdaCore|accessdate=Apr 4, 2023}}</ref><br/>[[Green Hills Software]] Optimising Ada 95 compiler,<br/>[[PTC (software company)|PTC]] ApexAda and ObjectAda,<ref>{{cite web|url=http://www.ptc.com/developer-tools/objectada |title=PTC ObjectAda |publisher=PTC.com |access-date=2014-01-27}}</ref><br/>MapuSoft Ada-C/C++ changer,<ref>{{cite web|url=https://www.mapusoft.com/ada-to-c-changer/|title=MapuSoft Ada-C/C++ changer|date=16 April 2019}}</ref> formerly known as "AdaMagic with C Intermediate",<ref>{{Cite web|url=http://ada-auth.org/cpl/details/151.html|title=Ada 95 Certified Processors List
| dialects = [[SPARK (programming language)|SPARK]], [[Ravenscar profile]]
| influenced = [[C++]], [[Chapel (programming language)|Chapel]],<ref
| license =
| released = {{Start date and age|1980|02}}
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}}
'''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 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, called Ada 2022 informally, is ISO/IEC 8652:2023.<ref name="ada-letters-june2023">{{cite journal | first=Luis Miguel | last=Pinho | 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=31 January 2024 | url=https://dl.acm.org/action/showFmPdf?doi=10.1145%2F3631483
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 used by the DoD at that time.<ref
== Features ==
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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.
A large number of [[Compile time|compile-time]] checks are supported to help avoid bugs that would not be detectable until run-time in some other languages or would require explicit checks to be added to the source code. For example, the syntax requires explicitly named closing of blocks to prevent errors due to mismatched end tokens. The adherence to strong typing allows detecting many common software errors (wrong parameters, range violations, invalid references, mismatched types, etc.) either during compile-time, or otherwise during run-time. As concurrency is part of the language specification, the [[compiler]] can in some cases detect potential [[Deadlock (computer science)|deadlocks.]]<ref>{{cite web|url=https://www.adaic.org/resources/add_content/docs/95style/html/sec_6/|title=Concurrency
Ada also supports [[Runtime system|run-time]] checks to protect against access to unallocated memory, [[buffer overflow]] errors, range violations, [[off-by-one error]]s, array access errors, and other detectable bugs. These checks can be disabled in the interest of runtime efficiency, but can often be compiled efficiently. It also includes facilities to help [[software verification|program verification]]. For these reasons, Ada is sometimes used in critical systems, where any [[anomaly in software|anomaly]] might lead to very serious consequences, e.g., accidental death, injury or severe financial loss. Examples of systems where Ada is used include [[avionics]], [[air traffic control]], [[Rail transport|railways]], banking, military and [[space technology]].<ref>{{cite web|title=Ada helps churn out less-buggy code|url=http://gcn.com/Articles/1999/06/30/Ada-helps-churn-out-lessbuggy-code.aspx|publisher=Government Computer News|access-date=2010-09-14|last1=Taft|first1=S. Tucker|last2=Olsen|first2=Florence|pages=2–3|date=1999-06-30|archive-date=2015-08-31|archive-url=https://web.archive.org/web/20150831211902/http://gcn.com/Articles/1999/06/30/Ada-helps-churn-out-lessbuggy-code.aspx|url-status=dead}}</ref><ref name="Ada_usage">{{cite web |last=Feldman |first=Michael |title=Who's Using Ada? Real-World Projects Powered by the Ada Programming Language November 2014 |url=https://www2.seas.gwu.edu/~mfeldman/ada-project-summary.html#Banking_and_Financial_Systems |publisher=SIGAda Education Working Group}}</ref>
{{anchor|Access type}}Ada's dynamic [[memory management]] is high-level and type-safe. Ada has no generic or untyped [[Pointer (computer programming)|pointers]]; nor does it implicitly declare any pointer type. Instead, all dynamic memory allocation and deallocation must occur via explicitly declared ''access types''. Each access type has an associated ''storage pool'' that handles the low-level details of memory management; the programmer can either use the default storage pool or define new ones (this is particularly relevant for [[Non-Uniform Memory Access]]). It is even possible to declare several different access types that all designate the same type but use different storage pools. Also, the language provides for ''accessibility checks'', both at compile time and at run time, that ensures that an ''access value'' cannot outlive the type of the object it points to.<ref>[https://youtube.com/watch?v=RyY01fRyGhM&t=419 no safe dynamic memory management in ADA], in: Writing Linux Kernel Modules in Safe Rust
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 does support a limited form of [[region-based memory management]]; also, creative use of storage pools can provide for a limited form of automatic garbage collection, since destroying a storage pool also destroys all the objects in the pool.
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== History ==
In the 1970s the [[United States Department of Defense|US Department of Defense]] (DoD) became concerned by the number of different programming languages being used for its embedded computer system projects, many of which were obsolete or hardware-dependent, and none of which supported safe modular programming. In 1975, a [[working group]], the [[High Order Language Working Group]] (HOLWG), was formed with the intent to reduce this number by finding or creating a programming language generally suitable for the department's and the [[Ministry of Defence (United Kingdom)|UK Ministry of Defence]]'s requirements. After many iterations beginning with an original [[Straw man proposal|straw-man proposal]]<ref>{{Cite web|url=http://iment.com/maida/computer/requirements/strawman.htm|title=DoD
HOLWG crafted the [[Steelman language requirements]], 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.
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Requests for proposals for a new programming language were issued and four contractors were hired to develop their proposals under the names of Red ([[Intermetrics]] led by Benjamin Brosgol), Green ([[Honeywell]], led by [[Jean Ichbiah]]), Blue ([[SofTech, Inc.|SofTech]], led by John Goodenough)<ref>{{cite web|url=http://www.sei.cmu.edu/about/people/jbg.cfm |title=John Goodenough | SEI Staff Profile |publisher=Sei.cmu.edu |access-date=2014-01-27}}</ref> and Yellow ([[SRI International]], led by Jay Spitzen).<!-- Though Intermetrics and Bull have previous links, I am including them for parallelism. --> In April 1978, after public scrutiny, the Red and Green proposals passed to the next phase. In May 1979, the Green proposal, designed by Jean Ichbiah at Honeywell, was chosen and given the name Ada—after Augusta Ada King, Countess of Lovelace, usually known as [[Ada Lovelace]]. This proposal was influenced by the language [[LIS (programming language)|LIS]] that Ichbiah and his group had developed in the 1970s. The preliminary Ada reference manual was published in ACM SIGPLAN Notices in June 1979. The Military Standard reference manual was approved on December 10, 1980 (Ada Lovelace's birthday), and given the number MIL-STD-1815 in honor of Ada Lovelace's birth year. In 1981, [[Tony Hoare]] took advantage of his [[Turing Award]] speech to criticize Ada for being overly complex and hence unreliable,<ref>{{cite journal |last=C.A.R. |first=Hoare |author-link=Tony Hoare |date=1981 |title=The Emperor's Old Clothes |url=http://zoo.cs.yale.edu/classes/cs422/2011/bib/hoare81emperor.pdf |url-status=live |journal=Communications of the ACM |publisher=[[Association for Computing Machinery]] |volume=24 |issue=2 |pages=75–83 |doi=10.1145/358549.358561 |s2cid=97895 |archive-url=https://web.archive.org/web/20160304012013/http://zoo.cs.yale.edu/classes/cs422/2011/bib/hoare81emperor.pdf |archive-date=2016-03-04 |doi-access=free}}</ref> but subsequently seemed to recant in the foreword he wrote for an Ada textbook.<ref>{{cite book |last1=Watt |first1=D.A. |last2=Wichmann |first2=B.A. |last3=Findlay |first3=W. |title=Ada: Language and Methodology |publisher=Prentice-Hall |date=1987}}</ref>
Ada attracted much attention from the programming community as a whole during its early days. Its backers and others predicted that it might become a dominant language for general purpose programming and not only defense-related work.<ref name="sward" /> Ichbiah publicly stated that within ten years, only two programming languages would remain: Ada and [[Lisp (programming language)|Lisp]].<ref name="SIGAda-Rosen">{{cite journal |last=Rosen |first=J-P. |title=The Ada Paradox(es) |journal=Ada Letters |publisher=ACM SIGAda |volume=24 |issue=2 |date=August 2009 |pages=28–35|doi=10.1145/1620593.1620597 |s2cid=608405
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 |url-status=dead}}</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
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=1983-04-11 |access-date=2015-06-07 |url-status=dead |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
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" />
Because of Ada's [[Safety-critical system|safety-critical]] support features, it is now used not only for military applications, but also in commercial projects where a software bug can have severe consequences, e.g., [[avionics]] and [[air traffic control]], commercial rockets such as the [[Ariane (rocket family)|Ariane 4 and 5]], [[satellite]]s and other space systems, railway transport and banking.<ref name="Ada_usage" />
For example, the [[Primary Flight Control System]], the [[Aircraft flight control systems|fly-by-wire]] system software in the [[Boeing 777]], was written in Ada, as were the fly-by-wire systems for the aerodynamically unstable [[Eurofighter Typhoon]],<ref>{{cite web |date=16 June 1999 |title=Agile thinking |url=https://www.flightglobal.com/agile-thinking/26933.article |url-status=live |archive-url=https://web.archive.org/web/20210415054346/https://www.flightglobal.com/agile-thinking/26933.article |archive-date=15 April 2021 |access-date=13 Feb 2024 |website=FlightGlobal}}</ref> [[Saab JAS 39 Gripen|Saab Gripen]],<ref>{{Cite web |last=Frisberg |first=Bo |title=Usage of Ada in the Gripen Flight Control System |url=https://www.sigada.org/conf/sa98/papers/frisberg.pdf |url-status=live |archive-url=https://web.archive.org/web/20240115002036/https://www.sigada.org/conf/sa98/papers/frisberg.pdf |archive-date=15 Jan 2024 |access-date=13 Feb 2024 |website=The Special Interest Group on Ada}}</ref> [[Lockheed Martin F-22 Raptor]] and the DFCS replacement flight control system for the [[Grumman F-14 Tomcat]]. The Canadian Automated Air Traffic System was written in 1 million lines of Ada ([[Source lines of code|SLOC]] count). It featured advanced [[distributed processing]], a distributed Ada database, and object-oriented design. Ada is also used in other air traffic systems, e.g., the UK's next-generation Interim Future Area Control Tools Support ({{proper name|iFACTS}}) air traffic control system is designed and implemented using [[SPARK (programming language)|SPARK]] Ada.<ref>{{cite web|last=AdaCore|title=GNAT Pro Chosen for UK's Next Generation ATC System|url=http://www.adacore.com/2007/06/19/adacore-gnat-pro-chosen-for-uk-next-generation/|access-date=2011-03-01|archive-url=https://web.archive.org/web/20101224163518/http://www.adacore.com/2007/06/19/adacore-gnat-pro-chosen-for-uk-next-generation/|archive-date=2010-12-24|url-status=dead}}</ref>
It is also used in the [[France|French]] [[Transmission Voie-Machine|TVM]] in-[[cab signalling]] system on the [[TGV]] high-speed rail system, and the metro suburban trains in Paris, London, Hong Kong and New York City.<ref name="Ada_usage" /><ref>{{cite web|last=AdaCore|title=Look Who's Using Ada|url=http://www.adacore.com/home/ada_answers/lookwho/|access-date=2011-03-01|archive-url=https://web.archive.org/web/20101224102110/http://www.adacore.com/home/ada_answers/lookwho|archive-date=2010-12-24|url-status=dead}}</ref>
== Standardization ==
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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.
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 83''', from the date of its adoption by ANSI, but is sometimes referred to also as '''Ada 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 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>
Work has continued on improving and updating the technical content of the Ada language. A Technical Corrigendum to Ada 95 was published in October 2001,<ref>
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>
On May 2, 2023, the Ada community saw the formal approval of publication of the '''Ada 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.
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=== Pragmas ===
A pragma is a [[compiler directive]] that conveys information to the compiler to allow specific manipulating of compiled output.<ref
Examples of common usage of compiler pragmas would be to disable certain features, such as run-time type checking or array subscript boundary checking, or to instruct the compiler to insert object code instead of a function call (as C/C++ does with [[inline function]]s).
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{{notelist}}
{{
== References ==
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