How to make screenshots in Doom

Newsgroups: rec.games.computer.doom,rec.games.computer.doom.help,etc.etc.
Subject: DOOM: Rec.Games.Computer.Doom FAQ (96/10/08)
From: fpv@xymph.iaf.nl (Frans P. de Vries)
Date: 16 Oct 1996 05:19:05 +0100

How can I take screenshots in DOOM, DOOM II, Heretic, Hexen, Strife?
Start them with 'doom -devparm', 'doom2 -devparm', 'heretic -ravpic',
'hexen -ravpic' or 'strife -devparm';
press F1 to create numbered .PCX files in the games' directory.