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The '''BLISS''' [[programming language]] was created at CMU in 1969. It was a high-level (in form) systems implementation language, which also provided accessibility to low-level aspects of the machine on which it ran. It shared many attributes with its predecessor [[BCPL]], including not having types, and being built around [[word]]s (unlike its contemporary systems implementation language, [[C programming language|C]]).

It did not have '[[jump|goto]]', but did have rich [[control flow]] capabilities, including the ability to terminate multiple levels of any kind of [[loop]]ing constructs (as if C's 'exit' statement took an [[argument]] specifying how many levels of loop to terminate). In BLISS, ''all'' references to a variable evaluate to the variable's [[address]]; for access to the ''contents'', it was necessary to explicitly use the 'contents of' [[operator]] ('.') (to again give a C analogy, it's as if all uses of variable names evaluated to [[pointer]]s to the variables, requiring the programmer to ''always'' say '*i' to get or replace the contents of 'i'). There are many other uncommon aspects (such as the 'machop' declaration to include [[object code]] in-line), but they will not be listed here.

It was originally intended for use on the [[PDP-10]], and as such, included a number of features intended to provide access to PDP-10 mechanisms, such as variable-width bytes in a PDP-10 word. It was shortly thereafter moved to the [[PDP-11]], forming the '''BLISS-11''' dialect (which was a [[cross-compiler]], as the [[compiler]] would not easily fit into a PDP-11 [[address space]]); the original became '''BLISS-10'''. Because of BLISS's goals of providing access to low-level aspects of the host machine, it required changes for the PDP-11, e.g. the provision of [[unsigned]] [[compare]]s, for use in comparing addresses.

Later, some effort was put into making it possible to write [[portable]] code in BLISS; its emphasis on words as the only datatype resulted in several versions for different word lengths: BLISS-16, BLISS-32, BLISS-36,etc.

In 1975, [[Digital Equipment Corporation|DEC]], which had sporadically been using BLISS internally for some years, decided to standardize on it for internal use in programming products; at the time, C had yet to really emerge from Bell, and the only serious competitor in the choice was [[Pascal]]. BLISS remained widely used inside DEC for may years, through the [[VAX]] and [[DEC Alpha|Alpha]] periods.

==External links==

* Ronald F. Brender∗,[https://www.cs.tufts.edu/~nr/cs257/archive/ronald-brender/bliss.pdf The BLISS programming language: a history]

[[Category: Languages]]

BLISS - Revision history

Jnc: Fairly complete