Embedded Software Engineer Question:

Volatile keyword is used to prevent compiler to optimize a variable which can change unexpectedly beyond compiler's comprehension. Suppose, we have a variable which may be changed from scope out of the program, say by a signal, we do not want the compiler to optimize it. Rather than optimizing that variable, we want the compiler to load the variable every time it is encountered. If we declare a variable volatile, compiler will not cache it in its register.