Main window

Move window from task bar to the system tray

Set it ON to remove CCCalc's button from Windows task bar and from Alt-Tab switch task list. It will put small icon to the system tray that allows to control CCCalc.

Minimize window on ESCAPE

If it is checked then ESCAPE key press will minimize CCCalc's window.

If you are active keyboard user then we recommend to set ON both of these settings. It is very convenient also to set up a hot key to the program's shortcut in Start menu.

Keyboard

Simulate NumLock mode

If checked then CCCalc will treat your key presses as if NumLock mode of your keyboard is set ON regardless of its real state.

Click sound on key press

If on then CCCalc will make click-like sound when valid key is pressed.

On Enter move caret to result of current expression

If on, then on Enter CCCalc will move the caret to result of the current expression creating it if necessary. Second Enter press will lead to creation of new expression at the bottom of the text.
See some more details here.