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 |
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.
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.
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):
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]
To 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 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 | 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 |
The Burroughs dialects included special system programming dialects such as ESPOL and NEWP.
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 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.
There are 35 such reserved words in the standard Burroughs Large Systems sub-language:
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|
|
|
|
There are 71 such restricted identifiers in the standard Burroughs Large Systems sub-language:
|
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|
|
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and also the names of all the intrinsic functions.
Priority | Operator | |
---|---|---|
first arithmetic | first | ↑ (power) |
second | ×, / (real), ÷ (integer) | |
third | +, - | |
second | <, ≤, =, ≥, >, ≠ | |
third | ¬ (not) | |
fourth | ∧ (and) | |
fifth | ∨ (or) | |
sixth | ⊃ (implication) | |
seventh | ≡ (equivalence) |
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; begininteger p, q; y := 0; i := k := 1; for p := 1 step 1 until n dofor q := 1 step 1 until m doif abs(a[p, q]) > y thenbegin y := abs(a[p, q]); i := p; k := q endend 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'
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 [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:
<nowiki/>BEGINFILEF(KIND=REMOTE);WRITE(F,<"HELLO WORLD!">);END.
An even simpler program using the Display statement:
BEGINDISPLAY("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 ’ .
<nowiki/>programHiFolks;beginprint‘Helloworld’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 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.
ALGOL is a family of imperative computer programming languages 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.
Atlas Autocode (AA) is a programming language developed around 1963 at the University of Manchester. A variant of the language ALGOL, it was developed by Tony Brooker and Derrick Morris for the Atlas computer. The initial AA and AB compilers were written by Jeff Rohl and Tony Brooker using the Brooker-Morris Compiler-compiler, with a later hand-coded non-CC implementation (ABC) by Jeff Rohl.
In computing, a compiler is a computer program that translates computer code written in one programming language into another language. The name "compiler" is primarily used for programs that translate source code from a high-level programming language to a low-level programming language to create an executable program.
Simula is the name of two simulation programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard. Syntactically, it is an approximate superset of ALGOL 60, and was also influenced by the design of Simscript.
Peter Naur was a Danish computer science pioneer and Turing award winner. He is best remembered as a contributor, with John Backus, to the Backus–Naur form (BNF) notation used in describing the syntax for most programming languages. He also contributed to creating the language ALGOL 60.
Backus-Naur form (BNF) is a notation used to describe the syntax of programming languages or other formal languages. It was developed by John Backus and Peter Naur. BNF can be described as a metasyntax notation for context-free grammars.
In computer science, a compiler-compiler or compiler generator is a programming tool that creates a parser, interpreter, or compiler from some form of formal description of a programming language and machine.
John Warner Backus was an American computer scientist. He directed the team that invented and implemented FORTRAN, the first widely used high-level programming language, and was the inventor of the Backus–Naur form (BNF), a widely used notation to define syntaxes of formal languages. He later did research into the function-level programming paradigm, presenting his findings in his influential 1977 Turing Award lecture "Can Programming Be Liberated from the von Neumann Style?"
In computer science, a high-level programming language is a programming language with strong abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language elements, be easier to use, or may automate significant areas of computing systems, making the process of developing a program simpler and more understandable than when using a lower-level language. The amount of abstraction provided defines how "high-level" a programming language is.
ALGOL W is a programming language. It is based on a proposal for ALGOL X by Niklaus Wirth and Tony Hoare as a successor to ALGOL 60. ALGOL W is a relatively simple upgrade of the original ALGOL 60, adding string, bitstring, complex number and reference to record data types and call-by-result passing of parameters, introducing the while
statement, replacing switch
with the case
statement, and generally tightening up the language.
In computer programming, a block or code block or block of code is a lexical structure of source code which is grouped together. Blocks consist of one or more declarations and statements. A programming language that permits the creation of blocks, including blocks nested within other blocks, is called a block-structured programming language. Blocks are fundamental to structured programming, where control structures are formed from blocks.
Peter John Landin was a British computer scientist. He was one of the first to realise that the lambda calculus could be used to model a programming language, an insight that is essential to the development of both functional programming and denotational semantics.
The history of programming languages spans from documentation of early mechanical computers to modern tools for software development. Early programming languages were highly specialized, relying on mathematical notation and similarly obscure syntax. Throughout the 20th century, research in compiler theory led to the creation of high-level programming languages, which use a more accessible syntax to communicate instructions.
ALGOL 58, originally named IAL, is one of the family of ALGOL computer programming languages. It was an early compromise design soon superseded by ALGOL 60. According to John Backus
The Zurich ACM-GAMM Conference had two principal motives in proposing the IAL: (a) To provide a means of communicating numerical methods and other procedures between people, and (b) To provide a means of realizing a stated process on a variety of machines...
The man or boy test was proposed by computer scientist Donald Knuth as a means of evaluating implementations of the ALGOL 60 programming language. The aim of the test was to distinguish compilers that correctly implemented "recursion and non-local references" from those that did not.
There are quite a few ALGOL60 translators in existence which have been designed to handle recursion and non-local references properly, and I thought perhaps a little test-program may be of value. Hence I have written the following simple routine, which may separate the man-compilers from the boy-compilers.
The TPK algorithm is a simple program introduced by Donald Knuth and Luis Trabb Pardo to illustrate the evolution of computer programming languages. In their 1977 work "The Early Development of Programming Languages", Trabb Pardo and Knuth introduced a small program that involved arrays, indexing, mathematical functions, subroutines, I/O, conditionals and iteration. They then wrote implementations of the algorithm in several early programming languages to show how such concepts were expressed.
Jensen's device is a computer programming technique that exploits call by name. It was devised by Danish computer scientist Jørn Jensen, who worked with Peter Naur at Regnecentralen. They worked on the GIER ALGOL compiler, one of the earliest correct implementations of ALGOL 60. ALGOL 60 used call by name. During his Turing Award speech, Naur mentions his work with Jensen on GIER ALGOL.
In computing, a compiler is a computer program that transforms source code written in a programming language or computer language, into another computer language. The most common reason for transforming source code is to create an executable program.
DG/L is a programming language developed by Data General Corp for the Nova, Eclipse, and Eclipse/MV families of minicomputers in the 1970s and early 1980s.
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