Where all to use volatile keyword in C

Question

I know volatile keyword prevents compiler from optimizing a variable and read it from memory whenever it is read. Apart from memory mapped registers, what are all the situat

Answer 1

Apart from memory mapped registers, what are all the situations where we need to use volatile?

If

1. execution is purely sequential (no threads and no signals delivered asynchronously);
2. you don't use longjmp;
3. you don't need to be able to debug a program compiled with optimizations;
4. you don't use constructs with vaguely specified semantics like floating point operations;
5. you don't do useless computations (computations where the result is ignored) as in a benchmark loop;
6. you don't do timings of any pure computations, that is anything that isn't I/O based (I/O based such as timings of accesses of network requests, external database accesses)

then you probably have no need for volatile.