Startup code



Hi all,

I am Ravikumar.N, new to embedded systems programming. I have
heard a term known as "startup Code" that will be executed in all the
processors.

Please tell me:
1) what is the meaning of "startup Code"
2) What function it does.
3) Who has to write the startup code.
4) What should be the contents of a "Startup Code".

With Regards,
Ravi Kumar.N

.