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ALGOL 68RS from RSRE was a portable compiler system written in ALGOL 68RS (bootstrapped from ALGOL 68R), and implemented on a variety of systems including the ICL 2900/Series 39, Multics and DEC VAX/VMS.

ALGOL 68RS is an implementation of ALGOL 68. Other implementations of ALGOL 68.

The language was based on the Revised Report, but with similar subset restrictions to ALGOL 68R. This compiler survives in the form of an Algol68-to-C compiler aka ELLA ALGOL 68.

Modules

ALGOL 68RS allow the programmer the ability of creating modules, these can be used by other programs and also allowed separate compilation.

Syntax: <lang algol68>PROGRAM [ (holelist ) ] progtitle [ CONTEXT holename IN progtitle ] [ USE uselist ] enclosed clause FINISH</lang> <lang algol68>DECS dectitle CONTEXT holename IN progtitle [ USE uselist ] decsbody KEEP keeplist FINISH</lang>

Example

PROGRAM (thinking, displaying) chess
BEGIN
  MODE PIECE = STRUCT(...);
  [12]PIECE pieces;
  ...
  HERE thinking(PIECE, pieces, BOARD, game);
  ...
  HERE displaying(PIECE, pieces, BOARD, game);
  ...
END</lang>

<lang algol68>PROGRAM thinkmodule
CONTEXT thinking IN chess
...
FINISH

An entire program can thus be composed of pieces of other modules, particularly if a hole contains a sub-hole (eg displaypiece), then this hole can in-turn be pulled into the composition.

Example: <lang algol68>PROGRAM abc COMPOSE game(thinking=thinkmodule, displaying=displayingmodule(piece=displaypiece)) FINISH</lang>