Jumping
From ZDoom Wiki
Jumping is not present in vanilla Doom and Heretic, but implemented in Hexen and Strife. ZDoom uses jumping values derived from Hexen. Jumping can be selectively enabled or disabled through MAPINFO map definitions and through the gameplay options menu. The console variables sv_allowjump and sv_nojump govern whether jumping is possible, possible if not disallowed by the map, or impossible.
