If you mean control character, in pawn by default it's '\'
In amxx, it's '^', because \ is already used a lot in HL, for exemple in menus.
You can change it to what you want, see page 119 :
http://www.compuphase.com/pawn/Pawn_Language_Guide.pdf
If i've misunderstood, and if you want to execute more than 1 command in a player console for example, then you can use ';'