ALGOL 68
<language> An extensive revision of {ALGOL 60} by Adriaan van
Wijngaarden et al. ALGOL 68 was discussed from 1963 by
Working Group 2.1 of {IFIP}. Its definition was accepted in
December 1968.
ALGOL 68 was the first, and still one of very few, programming
languages for which a complete formal specification was
created before its implementation. However, this
specification was hard to understand due to its formality, the
fact that it used an unfamiliar {metasyntax} notation (not
{BNF}) and its unconventional terminology.
One of the singular features of ALGOL 68 was its {orthogonal}
design, making for freedom from arbitrary rules (such as
restrictions in other languages that arrays could only be used
as parameters but not as results). It also allowed {user
defined data types}, then an unheard-of feature.
It featured {structural equivalence}; automatic type
conversion ("{coercion}") including {dereferencing}; {flexible
arrays}; generalised loops (for-from-by-to-while-do-od),
if-then-else-elif-fi, an integer case statement with an 'out'
clause (case-in-out-esac); {skip} and {goto} statements;
{blocks}; {procedures}; user-defined {operators}; {procedure
parameters}; {concurrent} execution (par-begin-end);
{semaphores}; generators "heap" and "loc" for {dynamic
allocation}. It had no {abstract data types} or {separate
compilation}.
(http://www.bookrags.com/research/algol-68-wcs/).
(2007-04-24)