Oberon is more than just a programming language, it's a full operating
system as well. Niklaus Wirth originally designed it for the Ceres
workstation (never heard of it personally), but has been ported to
other platforms, such as (you guessed it) the Macintosh. It is
genuinely extensible in that it works directly with procedures,
abandoning the concept of the program. A set of basic procedures comes
with the operating system with added functionality coming from modules
written and compiled by users. New procedures can be used as soon as
they are compiled since Oberon allows modules to be dynamically added
at run-time. The blurb from the Oberon people claims that the system
is approximately as fast as interpreted (as in BASIC) because the
compiler is quick and no linking is required.

See also: [MacOberon 1.21][1], [MacOberon 2.3][2], [MacOberon 3][3].

Compatibility
Architecture: 68k

  [1]: http://macintoshgarden.org/apps/macoberon-v121
  [2]: http://macintoshgarden.org/apps/macoberon-v23
  [3]: http://macintoshgarden.org/apps/macoberon-3