DOSBox

DOSBox is an emulator designed to allow MS-DOS games to be played on modern operating systems. Doom, Heretic, Hexen and others will generally run under DOSBox, although a fast computer is required for emulation at a playable speed; recent versions have greatly improved the performance.

DOSBox can be useful for running vanilla Doom and other original Doom-based DOS engines, although source ports are generally an easier, more advanced and likely the most popular way of playing classic Doom games.