Venetian blind crash

The Venetian blind crash occurs in Vanilla Doom in areas with a very high ceiling height. The name of the error comes from the "scanline" effect that causes every alternating horizontal line of pixels on the screen to be darkened. When the player experiences the crash, he or she is usually forced to restart the computer.

Venetian blind crashes are actually caused by ordinary program errors such as integer division by zero, segmentation/page faults, and illegal opcode execution. However, DOOM does not crash gracefully because it fails to shut down its libraries and unhook all interrupts when this happens. This leaves video, audio, and input unusable. Most DOS source ports immediately fixed this by changing the exit behavior and making sure everything is shut down completely even when a crash occurs.