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 begin and end pairs for delimiting them, representing a key advance in the rise of structured programming. ALGOL 60 was one of the first languages implementing function definitions (that could be invoked recursively). ALGOL 60 function definitions could be nested within one another (which was first introduced by any programming language), with lexical scope. It gave rise to many other languages, including CPL, PL/I, Simula, BCPL, B, Pascal, and C. Practically every computer of the era had a systems programming language based on ALGOL 60 concepts.
| Paradigms | procedural, imperative, structured |
|---|---|
| Family | ALGOL |
| Designed by | Backus, Bauer, Green, Katz, McCarthy, Naur, Perlis, Rutishauser, Samelson, van Wijngaarden, Vauquois, Wegstein, Woodger |
| First appeared | 1960 |
| Typing discipline | Static, strong |
| Scope | Lexical |
| Influenced by | |
| ALGOL 58 | |
| Influenced | |
| Most subsequent imperative languages (so-called ALGOL-like languages), e.g., PL/I, Simula, CPL, Pascal, Ada, 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.
Standardization
editALGOL 60 – with COBOL – were the first languages to seek standardization.
- ISO 1538:1984 Programming languages – ALGOL 60 (stabilized)
- ISO/TR 1672:1977 Hardware representation of ALGOL basic symbols ... (now withdrawn)
History
editALGOL 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.
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.[1]
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."[2]
The following people attended the meeting in Paris (from January 11 to 16):
- Friedrich Ludwig Bauer, Peter Naur, Heinz Rutishauser, Klaus Samelson, Bernard Vauquois, Adriaan van Wijngaarden, and Michael Woodger (from Europe)
- John Warner Backus, Julien Green, Charles Katz, John McCarthy, Alan Jay Perlis, and Joseph Henry Wegstein (from the USA).
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."
The language originally did not include recursion. It was inserted into the specification at the last minute, against the wishes of some of the committee.[3]
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."[4][5]
ALGOL 60 implementations timeline
editTo date there have been at least 70 augmentations, extensions, derivations and sublanguages of ALGOL 60.[6]
| Name | Year | Author | State | Description | Target CPU |
|---|---|---|---|---|---|
| X1 ALGOL 60 | August 1960[7] | Edsger W. Dijkstra and Jaap A. Zonneveld |  Netherlands |
First implementation of ALGOL 60[8] | Electrologica X1 |
| Algol | 1960[9] | Edgar T. Irons |  USA |
ALGOL 60 | CDC 1604 |
| Burroughs Algol (Several variants) |
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 midrange systems |
| 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[10] | 1962 | Thomas Eugene Kurtz, Stephen J. Garland, Robert F. Hargraves, Anthony W. Knapp, Jorge LLacer | USA |
ALGOL 60 | LGP-30 |
| Alcor Mainz 2002 | 1962 | Ursula Hill-Samelson, Hans Langmaack |  Germany |
Siemens 2002 | |
| ALCOR-Illinois 7090 | 1962 [11][12] |
Manfred Paul, Hans Rüdiger Wiehle, David Gries, and Rudolf Bayer | USA, West Germany
|
ALGOL 60 Implemented at Illinois and the TH München, 1962-1964 |
IBM 7090 |
| 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 60 | 1962 | Roland Strobel[13] |  East Germany |
Implemented by the Institute for Applied Mathematics, German Academy of Sciences at Berlin | Zeiss-Rechenautomat ZRA 1 |
| ALGOL 60 | 1962 | Bernard Vauquois, Louis Bolliet[14] |  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 W.L. van der Poel | Netherlands |
Staatsbedrijf der Posterijen, Telegrafie en Telefonie | ZEBRA |
| Kidsgrove Algol | 1963 | F. G. Duncan | UK |
English Electric Company KDF9 | |
| SCALP[15] | 1963 | Stephen J. Garland, Anthony W. Knapp, Thomas Eugene Kurtz | USA |
Self-Contained ALgol Processor for a subset of ALGOL 60 | LGP-30 |
| 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 |
| ALGOL 60 | 1964 | Jean-Claude Boussard[16] | France |
Institut d'informatique et mathématiques appliquées de Grenoble | IBM 7090 |
| ALGOL-GENIUS | 1964 | Börje Langefors | Sweden |
Added COBOL-inspired data records and I/O | Datasaab D-21 |
| ALGOL 60 | 1965 | Claude Pair[17] | France |
Centre de calcul de la Faculté des Sciences de Nancy | IBM 1620 |
| Dartmouth ALGOL | 1965 | Stephen J. Garland, Sarr Blumson, Ron Martin | USA |
ALGOL 60 | Dartmouth Time-Sharing System for the GE 235 |
| NU ALGOL | 1965 |  Norway |
UNIVAC | ||
| ALGOL 60 | 1965[18] | F.E.J. Kruseman Aretz | Netherlands |
MC compiler for the EL-X8 | Electrologica X8 |
| ALGEK | 1965 |  Soviet Union |
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 |
The Burroughs dialects included special system programming dialects such as ESPOL and NEWP.
Properties
editALGOL 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 provided two evaluation strategies for parameter passing: the common call-by-value, and call-by-name. The procedure declaration specified, for each formal parameter, which was to be used: value specified for call-by-value, and omitted for 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.[19] 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.
Call-by-name is known by many compiler designers 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 60 Reserved words and restricted identifiers
editThere are 35 such reserved words in the standard Burroughs Large Systems sub-language:
ALPHAARRAYBEGINBOOLEANCOMMENTCONTINUEDIRECTDODOUBLEELSEENDEVENTFALSEFILEFORFORMATGOIFINTEGERLABELLISTLONGOWNPOINTERPROCEDUREREALSTEPSWITCHTASKTHENTRUEUNTILVALUEWHILEZIP
There are 71 such restricted identifiers in the standard Burroughs Large Systems sub-language:
ACCEPTANDATTACHBYCALLCASECAUSECLOSEDEALLOCATEDEFINEDETACHDISABLEDISPLAYDIVDUMPENABLEEQLEQVEXCHANGEEXTERNALFILLFORWARDGEQGTRIMPININTERRUPTISLBLEQLIBERATELINELOCKLSSMERGEMODMONITORMUXNEQNONOTONOPENOROUTPICTUREPROCESSPROCUREPROGRAMDUMPRBREADRELEASEREPLACERESETRESIZEREWINDRUNSCANSEEKSETSKIPSORTSPACESWAPTHRUTIMESTOWAITWHENWITHWRITE
and also the names of all the intrinsic functions.
Standard operators
edit| Priority | Operator | |
|---|---|---|
| first arithmetic | first | ↑ (power) |
| second | ×, / (real), ÷ (integer) | |
| third | +, - | |
| second | <, ≤, =, ≥, >, ≠ | |
| third | ¬ (not) | |
| fourth | ∧ (and) | |
| fifth | ∨ (or) | |
| sixth | ⊃ (implication) | |
| seventh | ≡ (equivalence) | |
Examples and portability issues
editCode sample comparisons
editALGOL 60
editprocedure 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
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.
Following is an example of how to produce a table using Elliott 803 ALGOL:[20]
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'
ALGOL 60 family
editSince 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[21] at the University of Michigan-Dearborn Computer and Information Science Department Hello world! ALGOL Example Program page.[22]
BEGIN FILE F(KIND=REMOTE); EBCDIC ARRAY E[0:11]; REPLACE E BY "HELLO WORLD!"; WRITE(F, *, E); END.
Where * etc. represented a format specification as used in FORTRAN, e.g.[23]
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.
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 ’ .
program HiFolks;
begin
print ‘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 £ (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. Note use of '(', ')', and %.[24]
'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'
LEAP
editLEAP is an extension to the ALGOL 60 programming language which provides an associative memory of triples. The three items in a triple denote the association that an Attribute of an Object has a specific Value. LEAP was created by Jerome Feldman (University of California Berkeley) and Paul Rovner (MIT Lincoln Lab) in 1967. LEAP was also implemented in SAIL.
See also
editReferences
edit- ^ Knuth, Donald E. (December 1964). "Backus normal Form vs Backus Naur Form". Communications of the ACM. 7 (12): 735–6. doi:10.1145/355588.365140. S2CID 47537431.
- ^ ACM Award Citation / Peter Naur, 2005
- ^ van Emden, Maarten (2014). "How recursion got into programming: a tale of intrigue, betrayal, and advanced programming-language semantics". A Programmer's Place.
- ^ Hoare, C.A.R. (December 1973). "Hints on Programming Language Design" (PDF). p. 27. (This statement is sometimes erroneously attributed to Edsger W. Dijkstra, also involved in implementing the first ALGOL 60 compiler.)
- ^ Abelson, Hal; Dybvig, R. K.; et al. Rees, Jonathan; Clinger, William (eds.). "Revised(3) Report on the Algorithmic Language Scheme (Dedicated to the Memory of ALGOL 60)". Retrieved 2009-10-20.
- ^ The Encyclopedia of Computer Languages Archived September 27, 2011, at the Wayback Machine
- ^ Daylight, E. G. (2011). "Dijkstra's Rallying Cry for Generalization: the Advent of the Recursive Procedure, late 1950s – early 1960s". The Computer Journal. 54 (11): 1756–1772. doi:10.1093/comjnl/bxr002.
- ^ Kruseman Aretz, F.E.J. (30 June 2003). "The Dijkstra-Zonneveld ALGOL 60 compiler for the Electrologica X1" (PDF). Software Engineering. History of Computer Science. Amsterdam: Centrum Wiskunde & Informatica. ISSN 1386-3711. Archived from the original (PDF) on 2004-01-17.
- ^ Irons, Edgar T., A syntax directed compiler for ALGOL 60, Communications of the ACM, Vol. 4, p. 51. (Jan. 1961)
- ^ Kurtz, Thomas E. (1978). "BASIC". History of programming languages. pp. 515–537. doi:10.1145/800025.1198404. ISBN 0127450408.
- ^ Gries, D.; Paul, M.; Wiehle, H. R (1965). "Some techniques used in the ALCOR Illinois 7090". Communications of the ACM. 8 (8): 496–500. doi:10.1145/365474.365511. S2CID 18365024.
- ^ Bayer, R.; Gries, D.; Paul, M.; Wiehle, H. R. (1967). "The ALCOR Illinois 7090/7094 post mortem dump". Communications of the ACM. 10 (12): 804–808. doi:10.1145/363848.363866. S2CID 3783605.
- ^ Rechenautomaten mit Trommelspeicher, Förderverein der Technischen Sammlung Dresden
- ^ Mounier-Kuhn, Pierre (2014). "Algol in France: From Universal Project to Embedded Culture". IEEE Annals of the History of Computing. 36 (4): 6. ISSN 1058-6180.
- ^ Kurtz, op. cit., page 517.
- ^ Boussard, Jean-Claude (June 1964). Etude et réalisation d'un compilateur Algol60 sur calculateur éléctronique du type IBM 7090/94 et 7040/44 [Design and implementation of a compiler Algol60 on electronic calculator IBM 7090/94 and 7040/44] (PhD) (in French). Université Joseph-Fourier - Grenoble I.
- ^ Claude Pair (27 April 1965). Description d'un compilateur ALGOL. European Région 1620 Users Group. IBM.
- ^ Kruseman Aretz, F.E.J. (1973). An Algol 60 compiler in Algol 60. Mathematical Centre Tracts. Amsterdam: Mathematisch Centrum.
- ^ Aho, Alfred V.; Sethi, Ravi; Ullman, Jeffrey D. (1986). Compilers: Principles, Techniques, and Tools (1st ed.). Addison-Wesley. ISBN 978-0-201-10194-2., Section 7.5, and references therein
- ^ "803 ALGOL", the manual for Elliott 803 ALGOL
- ^ "The ALGOL Programming Language". www.engin.umd.umich.edu. Archived from the original on 10 February 2010. Retrieved 11 January 2022.
- ^ "Hello world! Example Program". www.engin.umd.umich.edu. Archived from the original on 4 February 2010. Retrieved 11 January 2022.
- ^ Fortran#"Hello, World!" example
- ^ "ICL 1900 series: Algol Language". ICL Technical Publication 3340. 1965.
Further reading
edit- Dijkstra, Edsger W. (1961). "ALGOL 60 Translation: An ALGOL 60 Translator for the X1 and Making a Translator for ALGOL 60 (PDF) (Technical report). Amsterdam: Mathematisch Centrum. 35.
- Randell, Brian; Russell, Lawford John (1964). ALGOL 60 Implementation: The Translation and Use of ALGOL 60 Programs on a Computer. Academic Press. OCLC 526731. The design of the Whetstone Compiler. One of the early published descriptions of implementing a compiler. See the related papers: Whetstone Algol Revisited, and The Whetstone KDF9 ALGOL Translator by Brian Randell
- Goos, Gerhard [in German] (2017-08-07). Geschichte der deutschsprachigen Informatik - Programmiersprachen und Übersetzerbau [History of informatics in German-speaking countries - Programming languages and compiler design] (PDF) (in German). Karlsruhe, Germany: Fakultät für Informatik, Karlsruhe Institute of Technology (KIT). Archived (PDF) from the original on 2022-05-19. Retrieved 2022-11-14. (11 pages)
External links
edit- Revised Report on the Algorithmic Language ALGOL 60 by Peter Naur, et al. ALGOL definition
- A BNF syntax summary of ALGOL 60
- "The Emperor's Old Clothes" – Hoare's 1980 ACM Turing Award speech, which discusses ALGOL history and his involvement
- MARST, a free ALGOL-to-C translator
- An Implementation of ALGOL 60 for the FP6000 Archived 2020-07-25 at the Wayback Machine Discussion of some implementation issues.
- Naur, Peter (August 1978). "The European Side of the Last Phase of the Development of ALGOL 60". ACM SIGPLAN Notices. 13 (8): 15–44. doi:10.1145/960118.808370. S2CID 15552479.
- Edinburgh University wrote compilers for Algol60 (later updated for Algol60M) based on their Atlas Autocode compilers initially bootstrapped from the Atlas to the KDF-9. The Edinburgh compilers generated code for the ICL1900, the ICL4/75 (an IBM360 clone), and the ICL2900. Here is the BNF for Algol60 Archived 2020-05-15 at the Wayback Machine and the ICL2900 compiler source Archived 2020-05-15 at the Wayback Machine, library documentation Archived 2020-05-15 at the Wayback Machine, and a considerable test suite Archived 2020-05-15 at the Wayback Machine including Brian Wichmann's tests. Archived 2020-05-15 at the Wayback Machine Also there is a rather superficial Algol60 to Atlas Autocode source-level translator Archived 2020-05-15 at the Wayback Machine.
- Eric S. Raymond's Retrocomputing Museum, among others a link to the NASE ALGOL 60 interpreter written in C.
- The NASE interpreter
- Stories of the B5000 and People Who Were There: a dedicated ALGOL computer [1], [2]
- Bottenbruch, Hermann (1961). Structure and Use of ALGOL 60 (Report). doi:10.2172/4020495. OSTI 4020495.
- NUMAL A Library of Numerical Procedures in ALGOL 60 developed at The Stichting Centrum Wiskunde & Informatica (legal successor of Stichting Mathematisch Centrum) legal owner.
- ALGOL 60 resources: translators, documentation, programs
- ALGOL 60 included in Racket