It's the game that redefined Co-Op games. Play locally via a network with up to 4 players through the single player campaign. You can play on the internet using various 3rd party utilities. Tons of versions available as well.
This page contains co-op info for Doom on the PC DOS [Classics]. All information about Doom was correct at the time of posting. Information is subject to change. If you see any errors please email us.