Hello All!

I'm newbie in unixes and in doubt in one question.
How we can change a euid of a process? Become a root for example.
The only possibility that i found is to exec() suid Program. Owner of the Program must be root. Is it the only way to change euid of a Program? or there is another possibility to change euid of a process to whatever i want. If so can i remove all set-uid-programs from my system? Or set-uid-programs is always the case (necessity) in all unixes?

PS sorry for my english. hope you understand the question.