Possibly the most elaborate and long-lived joke in the history of programming languages. It was designed on 1972-05-26 by Don Woods and Jim Lyons at Princeton University.
INTERCAL is purposely different from all other computer languages in all ways but one; it is purely a written language, being totally unspeakable. The INTERCAL Reference Manual, describing features of horrifying uniqueness, became an underground classic. An excerpt will make the style of the language clear:
It is a well-known and oft-demonstrated fact that a person whose work is incomprehensible is held in high esteem. For example, if one were to state that the simplest way to store a value of 65536 in a 32-bit INTERCAL variable is:
DO :1 <- #0$#256any sensible programmer would say that that was absurd. Since this is indeed the simplest method, the programmer would be made to look foolish in front of his boss, who would of course have happened to turn up, as bosses are wont to do. The effect would be no less devastating for the programmer having been correct.
INTERCAL has many other peculiar features designed to make it even more unspeakable. The Woods-Lyons implementation was actually used by many (well, at least several) people at Princeton.
Eric S. Raymond <firstname.lastname@example.org> wrote C-INTERCAL in 1990 as a break from editing "The New Hacker's Dictionary", adding to it the first implementation of COME FROM under its own name. The compiler has since been maintained and extended by an international community of technomasochists and is consequently enjoying an unprecedented level of unpopularity.
The version 0.9 distribution includes the compiler, extensive documentation and a program library. C-INTERCAL is actually an INTERCAL-to-C source translator which then calls the local C compiler to generate a binary. The code is thus quite portable.
["The INTERCAL Programming Language Reference Manual", Donald R. Woods & James M. Lyon].