const in function header

What are different possibilities that a const can appear in a function header, and what does each one do? Also, is something like this is possible?

Code:

---

void foo(int *a, int *b)*c
{
  ...
}

---

If so then what does that *c do there?

Moreover, in the following case (which I know can happen):

Code:

---

struct my_struct
{
  ...
}*z;

---

What's the function of *z?

Any help is appreciated.

>> What are different possibilities that a const can appear in a function header,
It can make a parameter const, it can make a return value const, and if the function is a member function it can make the function const within a class/struct.

>> is something like this is possible?
No.

>> What's the function of *z?
It is the same as saying my_struct* z; which is to declare a pointer to my_struct variable named z.

> What are different possibilities that a const can appear in a function header, and what does each one do?

When the function is a member of a class or struct and it will not alter the state of said class or struct.

EDIT: Daved reply to this question is more complete, than mine

> If so then what does that *c do there?

it generates a compile-time error.

> What's the function of *z?

to also generate a compile time error :)
Kidding... creates a pointer to my_struct called z.

thanks!