There were three major specifications:
Niklaus Wirth based his own Algol-W on ALGOL 60 before moving to develop Pascal. Algol-W was intended to be the next generation ALGOL but the ALGOL 68 committee decided on a design that was more complex and advanced rather than a cleaned simplified ALGOL 60. The official ALGOL versions are named after the year they were first published.
Algol68 is substantially different from Algol60 but was not well received so that in general "Algol" means dialects of Algol60.
The International Algorithmic Language (IAL) was extremely influential and is generally considered the ancestor of most of the modern programming languages (the so-called Algol-like languages). The Burroughs corporation built their line of computers to directly execute it. Additionally, in computer science, ALGOL object code was a simple and compact and stack-based instruction set architecture mainly used in teaching compiler construction and other high order language (of which Algol is generally considered the first) physical implementations such as Lisp machines and P-code machines.
ALGOL was used mostly by research computer scientists in the United States and in Europe. Its use in commercial applications was hindered by the absence of standard input/output facilities in its description and the lack of interest in the language by large computer vendors. ALGOL 60 did however become the standard for the publication of algorithms and had a profound effect on future language development.
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.
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."
The following people attended the meeting in Paris (from January 1 to 16):
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."
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.
|ZMMD-implementation||1958||Friedrich L. Bauer, Heinz Rutishauser, Klaus Samelson, Hermann Bottenbruch||Germany||implementation of ALGOL 58||Z22|
|Elliott ALGOL||1960||C. A. R. Hoare||UK||Subject of the famous Turing lecture||National-Elliott 803 & the Elliott 503|
|JOVIAL||1960||Jules Schwarz||US||Was the DOD HOL prior to Ada (programming language)||Various (see article)|
|Burroughs Algol |
|1961||Burroughs Corporation (with participation by Hoare, Dijkstra, and others)||US||Basis of the Burroughs (and now Unisys MCP based) computers|| Burroughs large systems |
and their midrange as well.
|Case ALGOL||1961||US||Simula was originally contracted as a simulation extension of the Case ALGOL||UNIVAC 1107|
|GOGOL||1961||Bill McKeeman||US||For ODIN time-sharing system||PDP-1|
|X1 Algol 60||1961||Edsger Dijkstra and J.A. Zonneveld||Netherlands||Mathematical Centre, Amsterdam||X1|
|Dartmouth ALGOL 30||1962||Thomas Eugene Kurtz et al||US||LGP-30|
|USS 90 Algol||1962||L. Petrone||Italy|
|Algol Translator||1962||G. van der May and W.L. van der Poel||Netherlands||Staatsbedrijf der Posterijen, Telegrafie en Telefonie||ZEBRA|
|Kidsgrove Algol||1963||F. G. Duncan||UK||English Electric Company KDF9|
|VALGOL||1963||Val Schorre||US||A test of the META II compiler compiler|
|Whetstone||1964||Brian Randell and L J Russell||UK||Atomic Power Division of English Electric Company. Precursor to Ferranti Pegasus (computer), National Physical Laboratories ACE (computer) and English Electric DEUCE implementations.||English Electric Company KDF9|
|ALGEK||1965||USSR||Minsk-22||АЛГЭК, based on ALGOL-60 and COBOL support, for economical tasks|
|MALGOL||1966||publ. A. Viil, M Kotli & M. Rakhendi,||Estonian SSR||Minsk-22|
|ALGAMS||1967||GAMS group (ГАМС, группа автоматизации программирования для машин среднего класса), cooperation of Comecon Academies of Science||Comecon||Minsk-22, later ES EVM, BESM|
|ALGOL/ZAM||1967||Poland||Polish ZAM computer|
|RegneCentralen ALGOL||1967||Peter Naur||Denmark|
|Simula 67||1967||Ole-Johan Dahl and Kristen Nygaard||Norway||Algol 60 with classes||UNIVAC 1107|
|Chinese Algol||1972||China||Chinese characters, expressed via the Symbol system|
|DG/L||1972||US||DG Eclipse family of computers|
ALGOL 60 allowed for two evaluation strategies for parameter passing: the common call-by-value, and call-by-name. Call-by-name had certain limitations in contrast to call-by-reference, making it an undesirable feature in imperative language design. For example, it is impossible in ALGOL 60 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. However, call-by-name is still beloved of ALGOL implementors for the interesting "thunks" that are used to implement it. Donald Knuth devised the "Man or boy test" to separate compilers that correctly implemented "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 grammars 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.
There are 71 such restricted identifiers in the standard Burroughs large systems sub-language:
WRITE and also the names of all the intrinsic functions.
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 transferred 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
Here's an example of how to produce a table using Elliott 803 ALGOL.
FLOATING POINT ALGOL TEST'
BEGIN REAL A,B,C,D'
FOR A:= 0.0 STEP D UNTIL 6.3 DO
B := SIN(A)'
C := COS(A)'
PUNCH(3) sends output to the teleprinter rather than the tape punch.
SAMELINE suppresses the carriage return + line feed normally printed between arguments.
ALIGNED(1,6) controls the format of the output with 1 digit before and 6 after the decimal point.
EBCDIC ARRAY E[0:11];
REPLACE E BY "HELLO WORLD!";
WRITE(F, *, E);
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 ‘ and ’.
print ‘Hello world’;
Here's a version for the Elliott 803 Algol (A104) The standard Elliott 803 used 5 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).
PRINT £HELLO WORLD££L???'
The ICL 1900 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.
'WRITE TEXT'("HELLO WORLD");
In the language of the "Algol 68 Report", Input/output facilities were collectively called the "Transput".
ALGOL 68 code was published with reserved words typically in lowercase, but bolded or underlined.
endOR using a specific transput channel:
putf((stand out,$gl$,"Hello, world!"))
For ease of programming computers with 7-bit characters of the time there were "official" methods to "BOLD" reserved words, for example, by using uppercase:
ENDNote: The 1964 Russian standard GOST 10859 allowed the encoding of 4-bit, 5-bit, 6-bit and 7-bit characters in ALGOL.