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 function definitions could be nested within one another (which was first introduced by any programming language[clarification needed]), with lexical scope.
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.
It was revised and expanded by Peter Naur for ALGOL 60, and at Donald Knuth's suggestion renamed Backus–Naur form.
ALGOL 60 provided two evaluation strategies for parameter passing: the common call-by-value, and call-by-name.
Donald Knuth devised the "man or boy test" to separate compilers that correctly implemented "recursion and non-local references."
Implementations differ in their hardware representations of underlined independent basic symbols[21] There are 24 reserved words in the Modified Report: 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.
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.
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[23] at the University of Michigan-Dearborn Computer and Information Science Department Hello world!
The ICT 1900 series Algol I/O version allowed input from paper tape or punched card.
[26] LEAP is an extension to the ALGOL 60 programming language which provides an associative memory of triples.
LEAP was created by Jerome Feldman (University of California Berkeley) and Paul Rovner (MIT Lincoln Lab) in 1967.