This function makes it easier to combine curves and straight lines. Furthermore, this drawing mode might be more intuitive for people new to OCAD.

First activate the option Curve mode: Change to straight line mode when clicking in drawing area in the Preferences -> Drawing and Editing tab.

Start drawing the curve as usual. To draw a straight line, just click in the drawing area. This way, you can easy switch between straight line mode and curve mode. Double click the left mouse button to finish drawing.

Animation and more information.