Basic Language for Implementation of System Software
BLISS
(BLISS, or allegedly, "System Software Implementation Language, Backwards") A language designed by W.A. Wulf at CMU around 1969.
BLISS is an expression language. It is block-structured, and typeless, with exception handling facilities, coroutines, a macro system, and a highly optimising compiler. It was one of the first non-assembly languages for operating system implementation. It gained fame for its lack of a goto and also lacks implicit dereferencing: all symbols stand for addresses, not values.
Another characteristic (and possible explanation for the backward acronym) was that BLISS fairly uniformly used backward keywords for closing blocks, a famous example being ELUDOM to close a MODULE. An exception was BEGIN...END though you could use (...) instead.
DEC introduced the NOVALUE keyword in their dialects to allow statements to not return a value.
Versions: CMU BLISS-10 for the PDP-10; CMU BLISS-11, BLISS-16, DEC BLISS-16C, DEC BLISS-32, BLISS-36 for VAX/VMS, BLISS-36C.
["BLISS: A Language for Systems Programming", CACM 14(12):780-790, Dec 1971].