ALGOL 60 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. ALGOL 60 was the first language implementing nested function definitions with lexical scope.
It gave rise to many other programming languages, including BCPL, B, Pascal, Simula 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.
Standardization ALGOL 60 — with COBOL — were the first
languages to seek standardization. ISO 1538:1984 Programming languages — Algol
60 ISO/TR 1672:1977 Hardware representation of
ALGOL basic symbols ... History
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. 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: Friedrich L. Bauer, Peter Naur, Heinz Rutishauser,
Klaus Samelson, Bernard Vauquois, Adriaan van Wijngaarden, and Michael Woodger
John W. Backus, Julien Green, Charles Katz, John McCarthy, Alan J. Perlis, and Joseph
Henry Wegstein. 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. C. A. R. 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.
ALGOL 60 implementations timeline To date there have been at least 70 augmentations,
extensions, derivations and sublanguages of Algol 60.
The Burroughs dialects included special Bootstrapping dialects such as ESPOL and NEWP.
Properties 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 facilities.
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 60 Reserved words and restricted identifiers
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. Standard Operators
Examples and portability issues Code sample comparisons
ALGOL 60
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.
Following is an example of how to produce a table using Elliott 803 ALGOL:
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 Since ALGOL 60 had no I/O facilities, there
is no portable hello world program in ALGOL. The following program could 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.
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 The standard Elliott 803 used 5 hole paper
tape and thus only had upper case. The code lacked any quote characters so £ was used
for open quote and ? for close quote. Special sequences were placed in double quotes.
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 %.
'PROGRAM' 'BEGIN'
'COMMENT' OPEN QUOTE IS '(', CLOSE IS ')', PRINTABLE SPACE HAS TO
BE WRITTEN AS % BECAUSE SPACES ARE IGNORED; WRITE TEXT('('HELLO%WORLD')');
'END' 'FINISH'
See also References
Further reading Dijkstra, Edsger W.. "ALGOL 60 Translation:
An ALGOL 60 Translator for the X1 and Making a Translator for ALGOL 60. Amsterdam: Mathematisch
Centrum. 35. Randell, B.; Russell, L.J.. 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 B. Randell External links
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
Discussion of some implementation issues. Naur, Peter. "The European Side of the Last
Phase of the Development of ALGOL 60". ACM SIGPLAN Notices 13: 15–44. doi:10.1145/960118.808370.
Edinburgh University wrote compilers for Algol60 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, and the ICL2900. Here is the BNF for Algol60 and the ICL2900
compiler source, library documentation, and a considerable test suite including Brian
Wichmann's tests. Also there is a rather superficial Algol60 to Atlas Autocode source-level translator.
Eric S. Raymond's Retrocomputing Museum, among others a link to the NASE Algol-60 interpreter
written in C. The NASE interpreter
Stories about Burrough's B5000 [1] NUMAL A Library of Numerical Procedures in
ALGOL 60 developed at The Stichting Centrum Wiskunde & Informatica legal owner.