Flow between game programs

The game code passes back and forth between two executables (START.EXE and TOS.EXE) via a batch script (DS.BAT).

START.EXE plays slideshow sequences like the opening credits, the animated nightmares, and the double visions (doll/alien).

TOS.EXE handles the interactive gameplay.

When TOS.EXE wants START.EXE to play a sequence, it writes the fifth byte of the five-byte PREFS file to signal which sequence, then terminates itself with an exit code. DS.BAT then proceeds to launch START.EXE, which reads PREFS and sees that fifth byte. START.EXE exits with an error code so DS.BAT launches TOS.EXE which (if appropriate) loads a special auto-save game and appears to continue from where it left off.