Is a main() required for a C program?

Question

Well the title says it all. Is a main() function absolutely essential for a C program?

I am asking this because I was looking at the Linux kernel code,

Answer 1

Paxdiablo's answer covers two of the cases where you won't encounter a main. Let me add a couple of more:

• Many plug-in systems for other programs (like, say, browsers or text editors or the like) have no main().
• Windows programs written in C have no main(). (They have a WinMain() instead.)