Algol 68 is a procedural language designed under the auspices of IFIP Working Group 2.1 as a successor to Algol 60
. The language is formally defined in the Revised Report on the Algorithmic Language Algol 68 by A. van Wijngaarden et al using a VW (2 level) grammar.
It is designed to be as orthogonal as possible and is block structured via the constructs: if - then - else - fi, case - in - out - esac, from - by - from - to - while - do. It is strongly typed with user definable modes and automatic de-referencing and coercion. Memory management is automatic, via garbage collection. Transput (I/O) is defined in the language and includes comprehensive formatting abilities.
It did not gain widespread popularity, possibly due to the price/availability of compilers, or its perceived complexity. In some ways it was ahead of its time and some features have influenced subsequent languages such as C++.