These variables can be read or modified from the console, during game play. The player can change them, to affect the program behavior.
"teamplay" // boolean, true if playing in teams. "samelevel" // boolean, if true, then cannot change level. "noexit" // boolean, true if can't exit level in deathmatch. "timelimit" // number of minutes the deathmatch will last. "fraglimit" // maximum number of frags before deathmatch ends. "skill" // text of skill message (?) "sv_gravity" // gravity pull, normal value is 800. "registered" // boolean, game is registered (do not change). "temp1" // to store custom floating point values
Beware that the variables you can read in Quake-C are those that are defined on the server, not those defined on the client. So if a player sets a value on his console, there is no chance that you can ever get this value (unless his console is also the server console).
Well, at least you can read values set by the server administrator, for what it's worth.