20 years of IF development systems

 * 1981 - DDL
 * 1983 - The Quill
 * 1985 - GAGS
 * 1986 - ADVSYS
 * 1987 - AGT
 * 1992 - ALAN
 * 1992 - TADS 2
 * 1994 - Inform 5
 * 1995 - Hugo
 * 1996 - Inform 6
 * 1997 - ADRIFT