prototyp declaration

[anarghya]

why do we need to use prototype for a function?
what does the header file contains?
why main function does not require any prototype declaration?

[pointers]

some functions returns values(like int,float) to the calling function.so the protype indicates which type it ireturns.

Lets assume int add()is some function used for addition........then this int represents ..... returns integer value.

int add()
{
c=a+b;
return c;
}

If a and b values are 2, 1.2 the addition becomes 3.2 it s an float value but this add function returns integer value to the caling function.

if protype is not defined means the default one is int(if the function returns any value)
in the case of main he default protype is void.void means it returns nothing(if function returns nothing means void is used).

[horace1]

there is good explaination of prototypes on URL
http://en.wikipedia.org/wiki/Function_prototype