I want to create a pie-chart. Is that possible with gnuplot and how to realize that?
Gnuplot is a "function plotting program". If you can come up with a function that has pie-like characteristics, Gnuplot will plot it for you. But I doubt that this would be done easily.
I'm afraid the answer is: No, that's not possible.
Edit: Apparently, that's also what the Gnuplot FAQ says.