Why is a point-to-volatile pointer, like “volatile int * p”, useful?

Question

volatile is to tell the compiler not to optimize the reference, so that every read/write does not use the value stored in register but does a real memory access

Answer 1

On the usefulness of volatile: This is needed, if you need to check memory, which is modified by hardware like a serial interface controller. It has its application in the world of embedded systems, where you work very close to the hardware without any OS in-between.