Pointer declared as constant as well as volatile

Question

While reading I came across this type of declaration and the following line -

const volatile char *p=(const volatile char *) 0x30;

Answer 1

Consider a read-only hardware register, of your network card for example.

It might change outside the control of the program, so the compiler is not allowed to cache its value in a register or optimize it away. Thus, volatile.

And it's read-only, so you shouldn't write to it. Thus, const.