An overview of the content of the 'historic' directory:

doompix1.exe	pre-release screenshots released on Mar 1, 1993
doomscn5.zip	pre-release screenshots released on Oct 5, 1993
doom0_2.zip	alpha version of DOOM released on Feb 4, 1993
doom0_4.zip	alpha version of DOOM released on Apr 2, 1993
doom0_5.zip	alpha version of DOOM released on May 22, 1993
doomprbt.zip	press-release beta version of DOOM released on Oct 4, 1993
doom1_0.zip	v0.99 shareware version of DOOM released on Dec 10, 1993
doom1_1.zip	v1.1 shareware version of DOOM released on Dec 16, 1993
altdoom1.zip	v1.1 alternate DOS extenders for DOOM released on Dec 15, 1993
doom1_2.zip	v1.2 shareware version of DOOM released on Feb 17, 1994
doom14bt.zip	v1.4beta shareware version of DOOM released on Jun 28, 1994
doom15bt.zip	v1.5beta shareware version of DOOM released on Jul 8, 1994
doom16bt.zip	v1.6beta shareware version of DOOM released on Aug 3, 1994
dm1666sw.zip	v1.666 shareware version of DOOM released on Sep 1, 1994
doom_v18.zip	v1.8 shareware version of DOOM released on Jan 23, 1995
