My low level is a tad rusty from when I learned the C side in school, but if I recall the not operator resolves as a single Boolean (0 or 1 in true C), whereas compliment comes back as however many bits you put in - a not operation per bit.
In C, the not operator is ! and the compliment operator is ~
Among many other duties I manage the safety and claims database for an outsourced industrial cleaning company and let me tell you, some of the plants my company works struggle to make it a week without an accident, meanwhile some will go years without an accident. We also have one plant which had its last accident during the Bush Administration. Its absolutely wild how much safety can vary from one industrial facility to another