This article is about the programming language. For other uses, see Algol (disambiguation).
|Paradigm||procedural, imperative, structured|
|Designed by||Backus, Bauer, Green, Katz, McCarthy, Naur, Perlis, Rutishauser, Samelson, van Wijngaarden, Vauquois, Wegstein, Woodger|
|Most subsequent imperative languages (so-called ALGOL-like languages), e.g. Simula, CPL, Pascal, Ada, C|
ALGOL 60 (short for Algorithmic Language 1960) is a member of the ALGOL family of computer programming languages. It followed on from ALGOL 58 which had introduced code blocks and the
end pairs for delimiting them. ALGOL 60 was the first language implementing nested function definitions with lexical scope. It gave rise to many other programming languages, including CPL, Simula, BCPL, B, Pascal and C.
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. Algol 68 is substantially different from Algol 60 and was criticised partially for being so, so that in general "Algol" refers to dialects of Algol 60.
ALGOL 60 — with COBOL — were the first languages to seek standardization.
ALGOL 60 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.
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 11 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." The Scheme programming language, a variant of 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.
To date there have been at least 70 augmentations, extensions, derivations and sublanguages of Algol 60.
|X1 ALGOL 60||August 1960||Edsger W. Dijkstra and Jaap A. Zonneveld||Netherlands||First implementation of ALGOL 60||Electrologica X1|
|Algol||1960||Edgar T. Irons||USA||Algol 60||CDC 1604|
|1961||Burroughs Corporation (with participation by Hoare, Dijkstra, and others)||USA||Basis of the Burroughs (and now Unisys MCP based) computers||Burroughs large systems |
and their midrange as well.
|Case ALGOL||1961||USA||Simula was originally contracted as a simulation extension of the Case ALGOL||UNIVAC 1107|
|GOGOL||1961||William M. McKeeman||USA||For ODIN time-sharing system||PDP-1|
|DASK ALGOL||1961||Peter Naur, Jørn Jensen||Denmark||Algol 60||DASK at Regnecentralen|
|SMIL ALGOL||1962||Torgil Ekman, Carl-Erik Fröberg||Sweden||Algol 60||SMIL at Lund University|
|GIER ALGOL||1962||Peter Naur, Jørn Jensen||Denmark||Algol 60||GIER at Regnecentralen|
|Dartmouth ALGOL 30||1962||Thomas Eugene Kurtz et al.||USA||LGP-30|
|USS 90 Algol||1962||L. Petrone||Italy|
|Elliott ALGOL||1962||C. A. R. Hoare||UK||Discussed in his 1980 Turing Award lecture||Elliott 803 & the Elliott 503|
|Algol Translator||1962||G. van der Mey 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||USA||A test of the META II compiler compiler|
|FP6000 Algol||1963||Roger Moore||Canada||written for Saskatchewan Power Corp||FP6000|
|Whetstone||1964||Brian Randell and Lawford John Russell||UK||Atomic Power Division of English Electric Company. Precursor to Ferranti Pegasus, National Physical Laboratories ACE 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|
|Chinese Algol||1972||China||Chinese characters, expressed via the Symbol system|
|DG/L||1972||USA||DG Eclipse family of Computers|
|NASE||1990||Erik Schoenfelder||Germany||Interpreter||Linux and MS Windows|
|MARST||2000||Andrew Makhorin||Russia||Algol-60 to C translator||All CPUs supported by the GNU Compiler Collection; MARST is part of the GNU project|
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 (ALGOL 68 parlance for Input/Output) facilities.
ALGOL 60 allowed for[clarification needed] two evaluation strategies for 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. Think of passing a pointer to swap(i, A[i]) in to a function. Now that every time swap is referenced, it's reevaluated. Say i := 1 and A[i] := 2, so every time swap is referenced it'll 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.
There are 35 such reserved words in the standard Burroughs large systems sub-language:
There are 71 such restricted identifiers in the standard Burroughs large systems sub-language:
and also the names of all the intrinsic functions.
|second||×, / (real), ÷ (integer)|
|second||<, ≤, =, ≥, >, ≠|
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 end end Absmax
Implementations differ in how the text in bold must be written. The word 'INTEGER', including the quotation marks, must be used in some implementations in place of integer, above, thereby designating it as a special keyword.
FLOATING POINT ALGOL TEST' BEGIN REAL A,B,C,D' READ D' FOR A:= 0.0 STEP D UNTIL 6.3 DO BEGIN PRINT PUNCH(3),££L??' B := SIN(A)' C := COS(A)' PRINT PUNCH(3),SAMELINE,ALIGNED(1,6),A,B,C' END' END'
Since ALGOL 60 had no I/O facilities, there is no portable hello world program in ALGOL. The following program could (and still will) compile and run on an ALGOL implementation for a Unisys A-Series mainframe, and is a straightforward simplification of code taken from The Language Guide at the University of Michigan-Dearborn Computer and Information Science Department Hello world! ALGOL Example Program page.
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:
BEGIN FILE F(KIND=REMOTE); WRITE(F, <"HELLO WORLD!">); END.
An even simpler program using the Display statement:
BEGIN DISPLAY("HELLO WORLD!") END.
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).
HIFOLKS' BEGIN PRINT £HELLO WORLD£L??' END'
'PROGRAM' (HELLO) 'BEGIN' 'COMMENT' OPEN QUOTE IS '(', CLOSE IS ')', PRINTABLE SPACE HAS TO BE WRITTEN AS % BECAUSE SPACES ARE IGNORED; WRITE TEXT('('HELLO%WORLD')'); 'END' 'FINISH'