v1.3 was leaked, but is commonly referred to as a 'bootleg' v1.4 due to a hacked executable showing a different, hardcoded version number.v1.2 made extensive changes to the engine and was the first version that could be run under Windows.v1.1 was the first registered version of the game.id chose to go with the latter numbering. v1.0, the first shareware version of the game, is called 'DOOM Operating System v0.99' in the start up text, but was distributed in DOOM1_0.ZIP.
