After a sketch has been loaded, the first executable line of code will be highlighted. Now press the Step Into button or the down arrow. Alternately, the F7 single step or F8 button may be pressed. The F9 button allows the program to be autorun with a 5ms interval (adjustable -see AutoStep in Edit Window) between steps. The interval can be set to 500ms to demonstrate in slow motion the operation of a sketch, or 1ms to run as fast as possible with minimal refresh.

The middle section of the screen displays the variables grid, and these are organised into Bytes, Chars, Int(eger)s, Long, Strings and  Defines. Any value in the grid can be changed by selecting it and typing in a new number.