Click the white square to draw D sets the plotting to drawing (G to redraw) and the y-axis goes from -1 to 1. T sets the plotting to typing (enter points then type 'done') and you can enter any number. Click space to calculate. M draws a magnitude spectrum and S shows the axis heights. P is used to change the precision of the drawing plotter (how many points it calculates). 3 is used to toggle whether it is written in terms of pi. 1 is used to toggle whether each point is normalised to have a gap of 1 or whether all point are between 0 and 1.
All by me. For the drawing graph, to get the best results, go really slowly. It is recommended to use small numbers as the maths becomes dodgy as the values increase. I am not making a FFT, it is fast enough.
