Each object in Creo TOOLKIT has a corresponding C typedef, called a “handle”, whose name is always the name of the object itself with the prefix “Pro.” The handle is used as the type for all variables and arguments that refer to an object of that type. For example, any Creo TOOLKIT function that performs an action on a solid has an input argument of type ProSolid.

Handles are classified into two types, depending on the way in which they are defined and have to be used. The two types are opaque handle (OHandle) and database handle (DHandle). The following sections describe these handles in detail.