View source for ALGOL

{{Short description|Family of programming languages}}
{{About|the programming language family||Algol (disambiguation)}}
{{Use dmy dates|date=February 2020}}
{{EngvarB|date=June 2022}}
{{Infobox programming language
| name = ALGOL
| logo = 1965 ALGOL-20 A Language Manual, Fierst et al - cover.jpg
| logo caption = A 1965 manual for ALGOL-20
| paradigm = [[Procedural programming|Procedural]], [[Imperative programming|imperative]], [[Structured programming|structured]]
| family = ALGOL
| designers = [[Friedrich Ludwig Bauer|Bauer]], [[Hermann Bottenbruch|Bottenbruch]], [[Heinz Rutishauser|Rutishauser]], [[Klaus Samelson|Samelson]], [[John Warner Backus|Backus]], [[Charles Katz|Katz]], [[Alan Jay Perlis|Perlis]], [[Joseph Henry Wegstein|Wegstein]], [[Peter Naur|Naur]], [[Bernard Vauquois|Vauquois]], [[Adriaan van Wijngaarden|van Wijngaarden]], [[Michael Woodger|Woodger]], [[Julien Green (computer scientist)|Green]], [[John McCarthy (computer scientist)|McCarthy]]
| released = {{Start date and age|1958}}
| typing = [[Static type|Static]], [[Strong and weak typing|strong]]
| scope = [[Scope (computer science)|Lexical]]
| implementations =
| influenced = Most subsequent imperative languages (including so-called ''ALGOL-like'' languages)<br/>e.g. [[PL/I]], [[Simula]], [[Pascal (programming language)|Pascal]], [[C (programming language)|C]] and [[Scheme (programming language)|Scheme]]
}}

'''ALGOL''' ({{IPAc-en|ˈ|æ|l|g|ɒ|l|,_|-|g|ɔː|l}}; short for "'''Algorithmic Language'''")<ref>The name of this language family is sometimes given in mixed case ([http://www.masswerk.at/algol60/report.htm ''Algol 60''] {{webarchive|url=https://web.archive.org/web/20070625171638/http://www.masswerk.at/algol60/report.htm |date=25 June 2007}}), and sometimes in all uppercase ([https://www.cs.ru.nl/~hubbers/courses/sl1/rr.pdf ''ALGOL68''] {{webarchive|url=https://web.archive.org/web/20140913132128/http://www.cs.ru.nl/~hubbers/courses/sl1/rr.pdf |date=13 September 2014}}). For simplicity this article uses ''ALGOL''.</ref> is a family of [[imperative programming|imperative]] computer [[programming language]]s originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for [[algorithm]] description used by the [[Association for Computing Machinery]] (ACM) in textbooks and academic sources for more than thirty years.<ref>[http://calgo.acm.org/ ''Collected Algorithms of the ACM''] {{webarchive|url=http://archive.wikiwix.com/cache/20111017235805/http://calgo.acm.org/ |date=17 October 2011}} Compressed archives of the algorithms. [[Association for Computing Machinery|ACM]].</ref>

In the sense that the [[Syntax (programming languages)|syntax]] of most modern languages is "Algol-like",<ref>{{cite web |url=http://www.eecs.qmul.ac.uk/~ohearn/Algol/intro.html |archive-url=https://web.archive.org/web/20111114122103/http://www.eecs.qmul.ac.uk/~ohearn/Algol/intro.html |title=Algol-like languages, Introduction |last1=O'Hearn |first1=P. W. |last2=Tennent |first2=R. D. |date=September 1996 |archive-date=14 November 2011}}</ref> it was arguably more influential than three other high-level programming languages among which it was roughly contemporary: [[FORTRAN]], [[Lisp (programming language)|Lisp]], and [[COBOL]].<ref>[http://groups.engin.umd.umich.edu/CIS/course.des/cis400/algol/algol.html "The ALGOL Programming Language"] {{webarchive|url=https://web.archive.org/web/20161006113915/http://groups.engin.umd.umich.edu/CIS/course.des/cis400/algol/algol.html |date=6 October 2016}}, University of Michigan-Dearborn</ref> It was designed to avoid some of the perceived problems with FORTRAN and eventually gave rise to many other programming languages, including [[PL/I]], [[Simula]], [[BCPL]], [[B (programming language)|B]], [[Pascal (programming language)|Pascal]], [[Ada (programming language)|Ada]], and [[C (programming language)|C]].

ALGOL introduced [[Block (programming)|code blocks]] and the <code>begin</code>...<code>end</code> pairs for delimiting them. It was also the first language implementing [[nested function]] definitions with [[lexical scope]]. Moreover, it was the first programming language which gave detailed attention to formal language definition and through the ''[[Algol 60#History|Algol 60 Report]]'' introduced [[Backus–Naur form]], a principal [[formal grammar]] notation for language design.

There were three major specifications, named after the years they were first published:
* [[ALGOL 58]] – originally proposed to be called ''IAL'', for ''International Algebraic Language''.
* [[ALGOL 60]] – first implemented as ''X1 ALGOL 60'' in 1961. Revised 1963.<ref name=":0">{{cite journal |title=Report on the Algorithmic Language ALGOL 60 |location=Copenhagen, Denmark |date=May 1960 |doi=10.1145/367236.367262 |issn=0001-0782 |author-first1=John Warner |author-last1=Backus |author-link1=John Warner Backus |author-first2=Friedrich Ludwig |author-last2=Bauer |author-link2=Friedrich Ludwig Bauer |author-first3=Julien |author-last3=Green |author-link3=Julien Green (computer scientist) |author-first4=Charles |author-last4=Katz |author-link4=Charles Katz |author-first5=John |author-last5=McCarthy |author-link5=John McCarthy (computer scientist) |author-first6=Peter |author-last6=Naur |author-link6=Peter Naur |author-first7=Alan Jay |author-last7=Perlis |author-link7=Alan Jay Perlis |author-first8=Heinz |author-last8=Rutishauser |author-link8=Heinz Rutishauser |author-first9=Klaus |author-last9=Samelson |author-link9=Klaus Samelson |author-first10=Bernard |author-last10=Vauquois |author-link10=Bernard Vauquois |author-first11=Joseph Henry |author-last11=Wegstein |author-link11=Joseph Henry Wegstein |author-first12=Adriaan |author-last12=van Wijngaarden |author-link12=Adriaan van Wijngaarden |author-first13=Michael |author-last13=Woodger |author-link13=Michael Woodger |editor-first=Peter |editor-last=Naur |editor-link=Peter Naur |journal=[[Communications of the ACM]] |volume=3 |issue=5 |pages=299–314 |s2cid=278290 |doi-access=free}}</ref><ref>{{cite web|title=Revised Report on the Algorithmic Language Algol 60|year=1963|url=http://www.masswerk.at/algol60/report.htm|access-date=8 June 2007 |archive-url=https://web.archive.org/web/20070625171638/http://www.masswerk.at/algol60/report.htm |archive-date=25 June 2007 |url-status=live}}</ref><ref>{{cite web|title=An ALGOL 60 Translator for the X1|year=1961|url=https://www.cs.utexas.edu/users/EWD/MCReps/MR35.PDF |archive-url=https://ghostarchive.org/archive/20221009/https://www.cs.utexas.edu/users/EWD/MCReps/MR35.PDF |archive-date=2022-10-09 |url-status=live|access-date=7 January 2021}}</ref>
* [[ALGOL 68]] – introduced new elements including flexible arrays, slices, parallelism, operator identification. Revised 1973.<ref name=a68>{{cite web|title=Revised Report on the Algorithmic Language ALGOL 68|year=1973|url=https://www.cs.ru.nl/~hubbers/courses/sl1/rr.pdf|access-date=13 September 2014|url-status=live|archive-url=https://web.archive.org/web/20140913132128/http://www.cs.ru.nl/~hubbers/courses/sl1/rr.pdf|archive-date=13 September 2014}}</ref>

ALGOL 68 is substantially different from ALGOL 60 and was not well received,{{according to whom|date=May 2023}} so reference to "Algol" is generally understood to mean ALGOL 60 and its dialects.{{citation needed|date=May 2023}}

==History==
ALGOL was developed jointly by a committee of European and American computer scientists in a meeting in 1958 at the [[ETH Zurich|Swiss Federal Institute of Technology in Zurich]] (cf. [[ALGOL 58]]).<ref>{{Cite web |title=History of ALGOL — Software Preservation Group |url=https://www.softwarepreservation.org/projects/ALGOL/ |access-date=2024-03-14 |website=www.softwarepreservation.org}}</ref> It specified three different syntaxes: a reference syntax, a publication syntax, and an implementation syntax, syntaxes that permitted it to use different keyword names and conventions for decimal points (commas vs periods) for different languages.<ref name=":0" />

ALGOL was used mostly by research computer scientists in the United States and in Europe; commercial applications were hindered by the absence of standard [[input/output]] facilities in its description, and the lack of interest in the language by large computer vendors (other than [[Burroughs Corporation]]).<ref name=":1" /> ALGOL 60 did however become the standard for the publication of algorithms and had a profound effect on future language development.<ref name=":1" />

[[File:Algol&Fortran family-by-Borkowski.svg|thumb|alt=caption|Family tree of the Algol, [[Fortran]] and [[COBOL]] programming language dynasty]]

[[John Backus]] developed the ''Backus normal form'' method of describing programming languages specifically for ALGOL 58. It was revised and expanded by [[Peter Naur]] for ALGOL 60, and at [[Donald Knuth]]'s suggestion renamed [[Backus–Naur form]].<ref>{{cite journal |last=Knuth |first=Donald E. |year=1964 |title=Backus Normal Form vs Backus Naur Form |journal=Communications of the ACM |volume=7 |issue=12 |pages=735–736 |doi=10.1145/355588.365140|s2cid=47537431 |doi-access=free }}</ref>

Peter Naur: "As editor of the [[ALGOL Bulletin]] I was drawn into the international discussions of the language and was selected to be member of the European language design group in November 1959. In this capacity I was the editor of the ALGOL 60 report, produced as the result of the ALGOL 60 meeting in Paris in January 1960."<ref name="naur_acm">[http://awards.acm.org/citation.cfm?id=1024454&srt=all&aw=140&ao=AMTURING&yr=2005 ACM Award Citation: Peter Naur] {{webarchive|url=https://wayback.archive-it.org/all/20120402220529/http://amturing.acm.org/award_winners/naur_1024454.cfm |date=2 April 2012}}, 2005</ref>

The following people attended the meeting in Paris (from 11 to 16 January):<ref name=":0" />
* [[Friedrich Ludwig Bauer]], [[Peter Naur]], [[Heinz Rutishauser]], [[Klaus Samelson]], [[Bernard Vauquois]], [[Adriaan van Wijngaarden]], and [[Michael Woodger]] (from Europe)
* [[John Warner Backus]], [[Julien Green (computer scientist)|Julien Green]], [[Charles Katz]], [[John McCarthy (computer scientist)|John McCarthy]], [[Alan Jay Perlis]], and [[Joseph Henry Wegstein]] (from the US).
Alan Perlis gave a vivid description of the meeting: "The meetings were exhausting, interminable, and exhilarating. One became aggravated when one's good ideas were discarded along with the bad ones of others. Nevertheless, diligence persisted during the entire period. The chemistry of the 13 was excellent."<ref>{{Cite book |last=Perlis |first=Alan J |chapter=The American side of the development of ALGOL |date=1978 |title=History of programming languages |chapter-url=https://dl.acm.org/doi/pdf/10.1145/800025.1198352 |pages=75–91 |doi=10.1145/800025.1198352 |isbn=0-12-745040-8 |via=dl.acm.org}}</ref>

===Legacy===
A significant contribution of the ALGOL 58 Report was to provide standard terms for programming concepts: statement, declaration, type, label, primary, block, and others.<ref name=":1">{{cite web |last1=Bemer |first1=Bob |title=A Politico-Social History of Algol |url=https://www.softwarepreservation.org/projects/ALGOL/paper/Bemer-Politico_Social_History_of_Algol.pdf |website=Computer History Museum |access-date=August 9, 2024}}</ref>

ALGOL 60 inspired many languages that followed it. [[Tony Hoare]] remarked: "Here is a language so far ahead of its time that it was not only an improvement on its predecessors but also on nearly all its successors."<ref>[http://www.eecs.umich.edu/~bchandra/courses/papers/Hoare_Hints.pdf "Hints on Programming Language Design"] {{webarchive|url=https://web.archive.org/web/20090915033339/http://www.eecs.umich.edu/~bchandra/courses/papers/Hoare_Hints.pdf |date=15 September 2009}}, C.A.R. Hoare, December 1973. Page 27. (This statement is sometimes erroneously attributed to [[Edsger W. Dijkstra]], also involved in implementing the first ALGOL 60 [[compiler]].)</ref> The [[Scheme (programming language)|Scheme]] programming language, a variant of [[Lisp (programming language)|Lisp]] that adopted the block structure and lexical scope of ALGOL, also adopted the wording "Revised Report on the Algorithmic Language Scheme" for its standards documents in homage to ALGOL.<ref name="r3rs">{{cite web |editor-last=Rees |editor-first=Jonathan |editor2-last=Clinger |editor2-first=William |editor3-last=Abelson |editor3-first=Hal |editor3-link=Hal Abelson |last=Dybvig |first=R. K. |title=Revised(3) Report on the Algorithmic Language Scheme, (Dedicated to the Memory of ALGOL 60) |url=http://groups.csail.mit.edu/mac/ftpdir/scheme-reports/r3rs-html/r3rs_toc.html |access-date=20 October 2009 | display-authors=etal |url-status=live |archive-url=https://web.archive.org/web/20100114060759/http://groups.csail.mit.edu/mac/ftpdir/scheme-reports/r3rs-html/r3rs_toc.html |archive-date=14 January 2010 | df=dmy-all}}</ref>

==Properties==
{{more citations needed section|date = February 2024}}
ALGOL 60 as officially defined had no [[I/O]] facilities; implementations defined their own in ways that were rarely compatible with each other. In contrast, ALGOL 68 offered an extensive library of ''transput'' (input/output) facilities.

ALGOL 60 allowed for two [[evaluation strategy|evaluation strategies]] for [[Parameter (computer science)|parameter]] passing: the common [[call-by-value]], and [[call-by-name]]. Call-by-name has certain effects in contrast to [[call-by-reference]]. For example, without specifying the parameters as ''value'' or ''reference'', it is impossible to develop a procedure that will swap the values of two parameters if the actual parameters that are passed in are an integer variable and an array that is indexed by that same integer variable.<ref>{{cite book |last1=Aho |first1=Alfred V. |author-link=Alfred V. Aho |last2=Sethi |first2=Ravi |author2-link=Ravi Sethi |last3=Ullman |first3=Jeffrey D. |author3-link=Jeffrey Ullman |title=[[Dragon Book (computer science)|Compilers: Principles, Techniques, and Tools]] |year=1986 |edition=1st |publisher=Addison-Wesley |isbn=0-201-10194-7}}, Section 7.5, and references therein</ref> Think of passing a pointer to swap(i, A[i]) in to a function. Now that every time swap is referenced, it is reevaluated. Say i := 1 and A[i] := 2, so every time swap is referenced it will return the other combination of the values ([1,2], [2,1], [1,2] and so on). A similar situation occurs with a random function passed as actual argument.

Call-by-name is known by many compiler designers for the interesting "[[thunk]]s" that are used to implement it. [[Donald Knuth]] devised the "[[man or boy test]]" to separate compilers that correctly implemented "[[recursion (computer science)|recursion]] and non-local references." This test contains an example of call-by-name.

ALGOL 68 was defined using a two-level grammar formalism invented by [[Adriaan van Wijngaarden]] and which bears his name. [[Van Wijngaarden grammar]]s use a [[context-free grammar]] to generate an infinite set of productions that will recognize a particular ALGOL 68 program; notably, they are able to express the kind of requirements that in many other programming language standards are labelled "semantics" and have to be expressed in ambiguity-prone natural language prose, and then implemented in compilers as ''ad hoc'' code attached to the formal language parser.

==Examples and portability==
{{expand section | with = further annotation indicating sources of code samples, as Wikipedia disallows presentation of individual editor creations or other original research | small = no |date=February 2024}}

===Code sample comparisons===

====ALGOL 60====
(The way the bold text has to be written depends on the implementation, e.g. 'INTEGER'—quotation marks included—for integer. This is known as [[stropping (programming)|stropping]].)

 '''procedure''' Absmax(a) Size:(n, m) Result:(y) Subscripts:(i, k);
     '''value''' n, m; '''array''' a; '''integer''' n, m, i, k; '''real''' y;
 '''comment''' The absolute greatest element of the matrix a, of size n by m,
     is copied to y, and the subscripts of this element to i and k;
 '''begin'''
     '''integer''' p, q;
     y := 0; i := k := 1;
     '''for''' p := 1 '''step''' 1 '''until''' n '''do'''
         '''for''' q := 1 '''step''' 1 '''until''' m '''do'''
             '''if''' abs(a[p, q]) > y '''then'''
                 '''begin''' y := abs(a[p, q]);
                     i := p; k := q
                 '''end'''
 '''end''' Absmax

Here is an example of how to produce a [[Table (information)|table]] using Elliott 803 ALGOL.<ref>[http://www.billp.org/ccs/A104/ "803 ALGOL"] {{webarchive|url=https://web.archive.org/web/20100529063048/http://www.billp.org/ccs/A104/ |date=29 May 2010}}, the manual for Elliott 803 ALGOL</ref>

  FLOATING POINT ALGOL TEST'
  BEGIN REAL A,B,C,D'
  READ D'
  FOR A:= 0.0 STEP D UNTIL 6.3 DO
  BEGIN
    PRINT {{abbr|PUNCH(3)|sends output to the teleprinter rather than the tape punch.}},££L??'
    B := SIN(A)'
    C := COS(A)'
    PRINT PUNCH(3),{{abbr|SAMELINE|suppresses the carriage return + line feed normally printed between arguments.}},{{abbr|ALIGNED(1,6)|controls the format of the output with one digit before and six after the decimal point.}},A,B,C'
  END
  END'

====ALGOL 68====
The following code samples are ALGOL 68 versions of the above ALGOL 60 code samples.

ALGOL 68 implementations used ALGOL 60's approaches to [[stropping (programming)|stropping]]. In ALGOL 68's case tokens with the bold typeface are reserved words, types (modes) or operators.

 '''proc''' abs max = ([,]'''real''' a, '''ref''' '''real''' y, '''ref''' '''int''' i, k)'''real''':
 '''comment''' The absolute greatest element of the matrix a, of size ⌈a by 2⌈a
 is transferred to y, and the subscripts of this element to i and k; '''comment'''
 '''begin'''
    '''real''' y := 0; i := ⌊a; k := 2⌊a;
    '''for''' p '''from''' ⌊a '''to''' ⌈a '''do'''
      '''for''' q '''from''' 2⌊a '''to''' 2⌈a '''do'''
        '''if''' '''abs''' a[p, q] > y '''then'''
            y := '''abs''' a[p, q];
            i := p; k := q
        '''fi'''
      '''od'''
    '''od''';
    y
 '''end''' # abs max #

Note: lower (⌊) and upper (⌈) bounds of an array, and array slicing, are directly available to the programmer.

 floating point algol68 test:
 (
   '''real''' a,b,c,d;
   &nbsp;
   # ''printf'' – sends output to the '''file''' ''stand out''. #
   # ''printf($p$);'' – selects a ''new page'' #
   printf(($pg$,"Enter d:"));  
   read(d);
   &nbsp;
   '''for''' step '''from''' 0 '''while''' a:=step*d; a <= 2*pi '''do'''
     printf($l$);  # ''$l$'' - selects a ''new line''. #
     b := sin(a);
     c := cos(a);
     printf(($z-d.6d$,a,b,c))  # formats output with 1 digit before and 6 after the decimal point. #
   '''od'''
 )

===Timeline: Hello world===
The variations and lack of portability of the programs from one implementation to another is easily demonstrated by the classic [[hello world program]].{{citation needed|date = February 2024}}

====ALGOL 58 (IAL)====
{{main|ALGOL 58}}
ALGOL 58 had no I/O facilities.

====ALGOL 60 family====
{{main|ALGOL 60}}
Since ALGOL 60 had no I/O facilities, there is no portable [[hello world program]] in ALGOL.
The next three examples are in Burroughs Extended Algol. The first two direct output at the interactive terminal they are run on. The first uses a character array, similar to C. The language allows the array identifier to be used as a pointer to the array, and hence in a REPLACE statement.
{{sxhl|2=m2|1=
 BEGIN
   FILE F(KIND=REMOTE);
   EBCDIC ARRAY E[0:11];
   REPLACE E BY "HELLO WORLD!";
   WRITE(F, *, E);
 END.
}}
A simpler program using an inline format:
{{sxhl|2=m2|1=
 BEGIN
   FILE F(KIND=REMOTE);
   WRITE(F, <"HELLO WORLD!">);
 END.
}}
An even simpler program using the Display statement. Note that its output would end up at the system console ('SPO'):

{{sxhl|2=m2|1= BEGIN DISPLAY("HELLO WORLD!") END.}}

An alternative example, using Elliott Algol I/O is as follows.  Elliott Algol used different characters for "open-string-quote" and "close-string-quote", represented here by {{color box|rgba(255,255,255,0)|border=silver|[[‘]]}} and {{color box|rgba(255,255,255,0)|border=silver|[[Single quotation mark|’]]}}.
{{sxhl|2=pascal|1=
 program HiFolks;
 begin
    print ‘Hello world’
 end;
}}
Below is a version from Elliott 803 Algol (A104). The standard Elliott 803 used five-hole paper tape and thus only had upper case.  The code lacked any quote characters so £ (UK Pound Sign) was used for open quote and ? (Question Mark) for close quote.  Special sequences were placed in double quotes (e.g£. £L?? produced a new line on the teleprinter).

   HIFOLKS'
   BEGIN
      PRINT £HELLO WORLD£L??'
   END'

The [[ICT 1900 series]] Algol I/O version allowed input from paper tape or punched card.  Paper tape 'full' mode allowed lower case.  Output was to a line printer. The open and close quote characters were represented using '(' and ')' and spaces by %.<ref>{{cite web|url=http://www.icl1900.co.uk/techpub/tp3340.djvu|title=ICL 1900 series: Algol Language|publisher=ICL Technical Publication 3340|year=1965}}</ref>
   'BEGIN'
      WRITE TEXT('('HELLO%WORLD')');
   'END'

====ALGOL 68====
{{main|ALGOL 68}}

'''ALGOL 68''' code was published with reserved words typically in lowercase, but bolded or underlined.
 '''begin'''
   printf(($gl$,"Hello, world!"))
 '''end'''
In the language of the "Algol 68 Report" the [[input/output]] facilities were collectively called the "Transput".

===Timeline of ALGOL special characters===
{{Contains special characters
| alt        = Decimal Exponent Symbol
| link       = http://mailcom.com/unicode/DecimalExponent.ttf
| special    = Unicode 6.0 "[https://www.unicode.org/charts/PDF/U2300.pdf Miscellaneous Technical]" characters
| fix        = Unicode#External_links
| characters = something like "₁₀" ([http://mailcom.com/unicode/DecimalExponent.ttf Decimal Exponent Symbol U+23E8 TTF])
}}
The ALGOLs were conceived at a time when character sets were diverse and evolving rapidly; also, the ALGOLs were defined so that only ''uppercase'' letters were required.

1960: [[IFIP]] – The Algol 60 language and report included several mathematical symbols which are available on modern computers and operating systems, but, unfortunately, were unsupported on most computing systems at the time. For instance: ×, ÷, ≤, ≥, ≠, ¬, ∨, ∧, ⊂, ≡, ␣ and ⏨.

1961 September: ASCII – The [[ASCII]] character set, then in an early stage of development, had the [[/|\]] (Back slash) character added to it in order to support ALGOL's [[Boolean data type|Boolean]] operators [[ALGOL 68#Dyadic operators with associated priorities|/\]] and [[ALGOL 68#Dyadic operators with associated priorities|\/]].<ref>[http://www.bobbemer.com/BACSLASH.HTM How ASCII Got Its Backslash] {{webarchive|url=https://web.archive.org/web/20140711225835/http://bobbemer.com/BACSLASH.HTM |date=11 July 2014}}, Bob Bemer</ref>

1962: [[ALCOR]] – This character set included the unusual "᛭"<!-- U+16ED --> runic cross<ref>[https://www.fileformat.info/info/unicode/char/16ed/ iron/runic cross]</ref> character for multiplication and the "⏨" Decimal Exponent Symbol<ref>[http://mailcom.com/unicode/DecimalExponent.ttf Decimal Exponent Symbol]</ref> for floating point notation.<ref>{{cite journal |last=Baumann |first=R. |title=ALGOL Manual of the ALCOR Group, Part 1 |journal=Elektronische Rechenanlagen |date=October 1961 |pages=206–212 |language=de|trans-title=ALGOL Manual of the ALCOR Group}}</ref><ref>{{cite journal |last=Baumann |first=R. |title=ALGOL Manual of the ALCOR Group, Part 2 |journal=Elektronische Rechenanlagen |volume=6 |date=December 1961 |pages=259–265 |language=de|trans-title=ALGOL Manual of the ALCOR Group}}</ref><ref>{{cite journal |last=Baumann |first=R. |title=ALGOL Manual of the ALCOR Group, Part 3 |journal=Elektronische Rechenanlagen |volume=2 |date=April 1962 |language=de|trans-title=ALGOL Manual of the ALCOR Group}}</ref>

1964: [[GOST]] – The 1964 Soviet standard [[GOST 10859]] allowed the encoding of 4-bit, 5-bit, 6-bit and 7-bit characters in ALGOL.<ref>{{cite web|title=GOST 10859 standard |url=http://homepages.cwi.nl/~dik/english/codes/stand.html#gost10859 |access-date=5 June 2007 |archive-url=https://web.archive.org/web/20070616201227/http://homepages.cwi.nl/~dik/english/codes/stand.html |archive-date=16 June 2007 |url-status=dead}}</ref>

1968: The "Algol 68 Report" – used extant ALGOL characters, and further adopted →, ↓, ↑, □, ⌊, ⌈, ⎩, ⎧, ○, ⊥, and ¢ characters which can be found on the [[IBM 2741]] keyboard with ''[[IBM Selectric typewriter|typeball]]'' (or ''golf ball'') [[Printer (computing)#Typewriter-derived printers|print heads]] inserted (such as the [[APL (programming language)#Hardware|APL golf ball]]). These became available in the mid-1960s while ALGOL 68 was being drafted.  The report was translated into Russian, German, French, and Bulgarian, and allowed programming in languages with larger character sets, e.g., [[Cyrillic]] alphabet of the Soviet [[BESM]]-4. All ALGOL's characters are also part of the [[Unicode]] standard and most of them are available in several popular [[font]]s.

2009 October: [[Unicode]] – The <code>⏨</code> (Decimal Exponent Symbol) for floating point notation was added to Unicode 5.2 for backward compatibility with historic [[Buran programme]] ALGOL software.<ref>{{cite web
 |url         = https://www.unicode.org/L2/L2008/08030r-subscript10.pdf
 |title       = Revised proposal to encode the decimal exponent symbol
 |last        = Broukhis
 |first       = Leonid
 |date        = 22 January 2008
 |website     = www.unicode.org
 |publisher   = ISO/IEC JTC 1/SC 2/WG 2
 |access-date = 24 January 2016
 |quote       = This means that the need to transcode GOST-based software and documentation can still arise: legacy numerical algorithms (some of which may be of interest, e.g. for the automatic landing of the Buran shuttle ...) optimized for the non-IEEE floating point representation of BESM-6 cannot be simply recompiled and be expected to work reliably, and some human intervention may be necessary.
 |url-status  = live
 |archive-url = https://web.archive.org/web/20150731024347/http://www.unicode.org/L2/L2008/08030r-subscript10.pdf
 |archive-date=31 July 2015
}}</ref>

==ALGOL implementations==
To date there have been at least 70 augmentations, extensions, derivations and sublanguages of Algol 60.<ref>{{cite web|url=http://hopl.murdoch.edu.au/showlanguage.prx?exp=1807 |title=The Encyclopedia of Computer Languages |access-date=20 January 2012 |url-status=dead |archive-url=https://web.archive.org/web/20110927014141/http://hopl.murdoch.edu.au/showlanguage.prx?exp=1807 |archive-date=27 September 2011 |df=dmy}}</ref>

{| class="wikitable sortable"
|-
!|Name
!|Year
!|Author
!|Country
!|Description
!|Target CPU
|-
| ZMMD-implementation|| 1958 || [[Friedrich L. Bauer]], Heinz Rutishauser, Klaus Samelson, Hermann Bottenbruch || {{flag|Germany}} || implementation of [[ALGOL 58]] || [[Z22 (computer)|Z22]] <br /> (later [[Konrad Zuse|Zuse]]'s [[Z23 (computer)|Z23]] was delivered with an Algol 60 compiler)<ref>[http://www.computerhistory.org/projects/zuse_z23/ Computer Museum History] {{webarchive|url=https://web.archive.org/web/20100820213805/http://www.computerhistory.org/projects/zuse_z23/ |date=20 August 2010}}, Historical Zuse-Computer Z23, restored by the Konrad Zuse Schule in Hünfeld, for the Computer Museum History Center in Mountain View (California) US</ref>
|-
|X1 ALGOL 60 || 1960 August<ref>{{cite journal |url=http://www.dijkstrascry.com/node/4 |title=Dijkstra's Rallying Cry for Generalization: the Advent of the Recursive Procedure, late 1950s – early 1960s |last=Daylight |first=E. G. |journal=[[The Computer Journal]] |year=2011 |doi=10.1093/comjnl/bxr002 |volume=54 |issue=11 |pages=1756–1772 |citeseerx=10.1.1.366.3916 |url-status=live |archive-url=https://web.archive.org/web/20130312111503/http://www.dijkstrascry.com/node/4 |archive-date=12 March 2013 }}</ref> || [[Edsger W. Dijkstra]] and [[:nl:Jaap Zonneveld|Jaap A. Zonneveld]] || {{flag|Netherlands}} || First implementation of ALGOL 60<ref>{{Cite book |last1 = Kruseman Aretz |first1 = F.E.J. | chapter = The Dijkstra-Zonneveld ALGOL 60 Compiler for the Electrologica X1 |title = Software Engineering | series = History of Computer Science |publisher = Centrum Wiskunde & Informatica | location = Amsterdam |date=30 June 2003 |url = http://oai.cwi.nl/oai/asset/4155/04155D.pdf |url-status=live |archive-url = https://web.archive.org/web/20160304191208/http://oai.cwi.nl/oai/asset/4155/04155D.pdf |archive-date=4 March 2016 }}</ref> || [[Electrologica X1]]
|-
|[[Elliott ALGOL]] || 1960s || [[C. A. R. Hoare]] || {{flag|UK}} || Subject of the 1980 [[Turing Award]] Lecture<ref>{{cite journal|first=Antony|last=Hoare|title=The Emperor's Old Clothes|journal=[[Communications of the ACM]]|volume=24|number=2|year=1980|pages=75–83|doi=10.1145/358549.358561|doi-access=free}}</ref>|| [[Elliott 803]], Elliott 503, Elliott 4100 series
|-
|[[JOVIAL]] || 1960 || [[Jules Schwartz]] || {{flag|US}} || A [[United States Department of Defense|DOD]] [[High level language|HOL]] prior to [[Ada (programming language)|Ada]] || Various (see article)
|-
|[[Burroughs Large Systems#ALGOL|Burroughs Algol]] <br /> (Several variants)|| 1961 || [[Burroughs Corporation]] (with participation by Hoare, [[Edsger W. Dijkstra|Dijkstra]], and others) || {{flag|US}} || Basis of the [[Burroughs Corporation|Burroughs]] (and now [[Unisys]] [[Burroughs MCP|MCP]] based) computers || [[Burroughs Large Systems]] and their midrange also.
|-
|[[Case ALGOL]] || 1961 || [[Case Western Reserve University|Case Institute of Technology]]<ref>{{cite web|last=Koffman|first=Eliot|title=All I Really Need to Know I Learned in CS1|url=http://www.temple.edu/cis/directory/tenure/documents/KoffmanSIGCSESlides.pdf|access-date=20 May 2012|url-status=dead|archive-url=https://web.archive.org/web/20121012032624/http://www.temple.edu/cis/directory/tenure/documents/KoffmanSIGCSESlides.pdf|archive-date=12 October 2012}}</ref> || {{flag|US}} || [[Simula]] was originally contracted as a simulation extension of the Case ALGOL || [[UNIVAC 1107]]
|-
|[[GOGOL]] || 1961 || [[William M. McKeeman]] || {{flag|US}} || For ODIN time-sharing system<ref>{{cite web|url=http://hopl.info/showlanguage.prx?exp=3905|title=GOGOL – PDP-1 Algol 60 (Computer Language)|access-date=1 February 2018|publisher=Online Historical Encyclopaedia of Programming Languages|url-status=live|archive-url=https://web.archive.org/web/20180202074636/http://hopl.info/showlanguage.prx?exp=3905|archive-date=2 February 2018}}</ref> || [[PDP-1]]
|-
|[[RegneCentralen ALGOL]] || 1961 || [[Peter Naur]], [[Jørn Jensen]] || {{flag|Denmark}} || Implementation of full Algol 60 || DASK at Regnecentralen
|-
|[[Dartmouth ALGOL 30]] || 1962 || [[Thomas Eugene Kurtz]] et al. || {{flag|US}} ||  || [[LGP-30]]
|-
|[[USS 90 Algol]] || 1962 || [[L. Petrone]] <!-- ? --> || {{flag|Italy}} ||
|-
|ALGOL 60
|1962
|[[Bernard Vauquois]], Louis Bolliet<ref>{{Cite journal |last=Mounier-Kuhn |first=Pierre |date=2014 |title=Algol in France: From Universal Project to Embedded Culture |url=https://www.academia.edu/79159820 |journal=IEEE Annals of the History of Computing |volume=36 |issue=4 |pages=6–25 |doi=10.1109/MAHC.2014.50 |bibcode=2014IAHC...36d...6M |s2cid=16684090 |issn=1058-6180}}</ref>
| {{flag|France}}
|Institut d'Informatique et Mathématiques Appliquées de Grenoble (IMAG) and Compagnie des Machines Bull
|[[Bull Gamma 60]]
|-
| Algol Translator || 1962 || G. van der Mey and [[Willem van der Poel|W.L. van der Poel]] || {{flag|Netherlands}} || Staatsbedrijf der Posterijen, Telegrafie en Telefonie || [[ZEBRA (computer)|ZEBRA]]
|-
|[[Kidsgrove Algol]] || 1963 || [[F. G. Duncan]] <!-- ? --> || {{flag|UK}} ||  || [[English Electric|English Electric Company]] [[English Electric KDF9|KDF9]]
|-
|[[VALGOL]] || 1963 || [[Val Schorre]] || {{flag|US}} || A test of the [[META II]] compiler compiler
|-
|[[Whetstone (benchmark)|Whetstone]] || 1964 || [[Brian Randell]] and L. J. Russell || {{flag|UK}} || Atomic Power Division of English Electric Company. Precursor to [[Ferranti Pegasus]], National Physical Laboratories [[Automatic Computing Engine|ACE]] and [[English Electric DEUCE]] implementations. || English Electric Company [[English Electric KDF9|KDF9]]
|-
|[[NU ALGOL]] || 1965 || || {{flag|Norway}} || || [[UNIVAC]]
|-
|ALGEK || 1965 || || {{flag|USSR}} || АЛГЭК, based on ALGOL-60 and [[COBOL]] support, for economical tasks || [[Minsk family of computers|Minsk-22]]
|-
|[[ALGOL W]] || 1966 || [[Niklaus Wirth]] || {{flag|US}} || Proposed successor to ALGOL 60 ||  [[IBM System/360]]
|-
|[[MALGOL]] || 1966 || publ. A. Viil, M Kotli & M. Rakhendi, || {{flag|Estonian SSR}} || || [[Minsk family of computers|Minsk-22]]
|-
|[[ALGAMS]] || 1967 || GAMS group (ГАМС, группа автоматизации программирования для машин среднего класса), cooperation of Comecon Academies of Science || [[Comecon]] || || [[Minsk family of computers|Minsk-22]], later [[ES EVM]], [[BESM]]
|-
|[[ALGOL/ZAM]] || 1967 || || {{flag|Poland}} || || Polish [[ZAM (computer)|ZAM]] computer
|-
|[[Simula|Simula 67]] || 1967 || [[Ole-Johan Dahl]] and [[Kristen Nygaard]] || {{flag|Norway}} || Algol 60 with classes || [[UNIVAC 1107]]
|-
|{{anchor|Triplex}}[[Triplex-ALGOL Karlsruhe]] || 1967/1968 ||  || [[Karlsruhe]], {{flag|Germany}} || ALGOL 60 (1963) with [[triplex number]]s for [[interval arithmetic]] || <ref name="Wippermann_1968">{{cite journal |title=Definition von Schrankenzahlen in Triplex-ALGOL |language=de |author-first=Hans-Wilm |author-last=Wippermann |date=1968 |orig-date=1967-06-15, 1966 |journal=[[Computing (journal)|Computing]] |issn=0010-485X |publisher=Springer |volume=3 |issue=2 |location=Karlsruhe, Germany |doi=10.1007/BF02277452 |s2cid=36685400 |pages=99–109}}</ref>
|-
|[https://web.archive.org/web/20080722231533/http://hopl.murdoch.edu.au/showlanguage.prx?exp=7288&language=Chinese%20Algol Chinese Algol]|| 1972 || 
| {{flag|China}} || Chinese characters, expressed via the Symbol system
|-
|[[DG/L]] || 1972 || || {{flag|US}} || || DG [[Data General Eclipse|Eclipse]] family of Computers
|-
|[[S-algol]] || 1979 || [[Ron Morrison]] || {{flag|UK}} || Addition of orthogonal datatypes with intended use as a teaching language || [[PDP-11]] with a subsequent implementation on the [[Java virtual machine|Java VM]]
|}

The Burroughs dialects included special Bootstrapping dialects such as [[Executive Systems Problem Oriented Language|ESPOL]] and [[NEWP]].  The latter is still used for Unisys MCP system software.

==See also==
{{div col|content=
* [[Address (programming language)]]
* [[Atlas Autocode]]
* [[Coral 66]]
* [[Edinburgh IMP]]
* [[ISWIM]]
* [[JOVIAL]]
* [[NELIAC]]
* [[Simula]]
* [[S-algol]]
* [[Scheme (programming language)]]
}}

==References==
{{reflist|30em}}

==Further reading==
* {{cite book |author=Randell, Brian & L. J. Russell |date=1964 |title=ALGOL 60 Implementation: The Translation and Use of ALGOL 60 Programs on a Computer |location= |publisher=Academic Press |citeseerx=10.1.1.737.475 |url=http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.737.475&rep=rep1&type=pdf |access-date=}}. On the design of the [[Whetstone Compiler]], and one of the early published descriptions of implementing a compiler.
* {{cite web |first=E. W |last=Dijkstra |title=ALGOL 60 Translation: An ALGOL 60 Translator for the X1 and Making a Translator for ALGOL 60 |series=report MR 35/61 |publisher=Mathematisch Centrum |place=Amsterdam |year=1961 |url=http://www.cs.utexas.edu/users/EWD/MCReps/MR35.PDF |archive-url=https://ghostarchive.org/archive/20221009/http://www.cs.utexas.edu/users/EWD/MCReps/MR35.PDF |archive-date=2022-10-09 |url-status=live}}
* {{cite web |first=Frans E.J. |last=Kruseman Aretz |title=The Dijkstra–Zonneveld ALGOL 60 Compiler for the Electrologica X1 |series=Historical note SEN, 2 |place=Amsterdam: Centrum voor Wiskunde en Informatica |url=https://ir.cwi.nl/pub/4155/04155D.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://ir.cwi.nl/pub/4155/04155D.pdf |archive-date=2022-10-09 |url-status=live}}

==External links==
* [http://www.masswerk.at/algol60/report.htm Revised Report on the Algorithmic Language Algol 60 by Peter Naur, et al.]
* [http://portal.acm.org/ft_gateway.cfm?id=808370&type=pdf&coll=&dl=ACM&CFID=15151515&CFTOKEN=6184618 The European Side of the Last Phase of the Development of ALGOL 60, by Peter Naur]
* [http://www.softwarepreservation.org/projects/ALGOL/ A History of ALGOL] from the [[Computer History Museum]]

{{ALGOL programming}}
{{Authority control}}

{{DEFAULTSORT:Algol}}
[[Category:ALGOL 60 dialect]]
[[Category:Algol programming language family| ]]
[[Category:Articles with example ALGOL 60 code]]
[[Category:Computer-related introductions in 1958]]
[[Category:Procedural programming languages]]
[[Category:Programming languages created in 1958]]
[[Category:Structured programming languages]]
[[Category:Systems programming languages]]