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An extensive revision of ALGOL 60 by Adriaan vanWijngaarden et al. ALGOL 68 was discussed from 1963 byWorking Group 2.1 of IFIP. Its definition was accepted inDecember 1968.ALGOL 68 was the first, and still one of very few, programminglanguages for which a complete formal specification wascreated before its implementation. However, thisspecification was hard to understand due to its formality, thefact that it used an unfamiliar metasyntax notation (notBNF) and its unconventional terminology.One of the singular features of ALGOL 68 was its orthogonaldesign, making for freedom from arbitrary rules (such asrestrictions in other languages that arrays could only be usedas parameters but not as results). It also allowed userdefined data types, then an unheard-of feature.It featured structural equivalence; automatic typeconversion ("coercion") including dereferencing; flexiblearrays; 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; procedureparameters; concurrent execution (par-begin-end);semaphores; generators "heap" and "loc" for dynamicallocation. It had no abstract data types or separatecompilation. (http://www.bookrags.com/research/algol-68-wcs/).