Open C++ contains many helper classes that are needed to pass data into and out of methods defined on other classes. For example, ThruPoint objects are used to specify the location, slope, and curvature of points along a UgSpline curve.
//Initialize pSpline pointer
std::vector <ThruPoint> thruPts; //Array of ThruPoint objects
std::vector <double> params; //Array of doubles
//Get defining data for a spline
pSpline->getThruPoints(&periodic, &order, &thruPts, ¶m);
Note that helper classes are not named with the "UG" prefix.