Review your trignometry, Sine, Cosine to be exact.
There are ways to do it without trig, but trig is the simplest!
You can also do it with two bitmaps. One contains an image.
The second contains an alpha gradient. Ranging from 0% and the other 100%. The alpha percentile indicates how wide to cut the notch in the pie! Essentially the two pie pieces are alpha blit into each other and the background.
In standard C? Use characters to draw the pie chart (such as asterisk or pound sign). You can hard code the circle, or use one of the circle algorithms such as this. To draw lines in the circle, use one of the line algorithms such as this.