? defines a variable for a supergenie (graphical subroutine on a pop-up page).
% defines a variable for a genie (simple graphical subroutine).
whatever you are willing to program in CiCode (Citect's own language) or VB.
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For the long answers: turn to the Citect help file.
If you don't have it: download CitectSCADA as a whole on the Citect website .