http://www.imdb.com/title/tt0070904/
This movie about a virtual reality simulation that programmers create, similar to TheThirteenthFloor or TheMatrix. This is an oldie and so many original ideas came from this movie way before TheMatrix or TheThirteenthFloor.
It is based on the science fiction novel Simulacron-3.
The movie is in German with subtitles.
See also: TheMatrix, TheThirteenthFloor, DarkCity