How does one perfect curves in a logo like the "Mcdonalds" M arches? - what was logo for mcdonalds before im lovin it

You see all the time on the jerseys of the perfectly drawn characters and symbols and signs, on average, tools like a compass or a customized work order. How are they? some complex computer programs? a mathematical equation? Graphic? or just a very clever artist?

responds with an example would be greatly appreciated