focal (FOCAL language interpreter)

FOCAL is an interactive interpreted programming language based on JOSS
and mostly used on DEC PDP series machines. It is an ancestor of (or
at least an influence on) the BASIC language. For more information on
FOCAL, see: https://en.wikipedia.org/wiki/FOCAL_(programming_language)

This implementation is by Dave Conroy and Akira KIDA. It comes from Eric
Raymond and John Cowan's Retrocomputing Museum:
http://www.catb.org/retro/

See /usr/doc/focal-$VERSION/focal_doc.txt for the language
specification. See /usr/share/focal for sample code. Loading and
running a FOCAL program is done like so:

  $ focal
  *lib call program.foc
  *g

Enter "quit" at the * prompt to exit.

There is a small archive of FOCAL programs available here:
ftp://ftp.pdp8.net/software/games/focal/
...although not all of them are compatible with this version of FOCAL.