Can a variable be both const and volatile? Give a real example.

Yes. A const volatile variable is one the program must not write to, but whose value can still change externally. The classic example is a read-only hardware status register: it is const because the software should never write to it (and the compiler will error if you try), and volatile because the hardware updates it asynchronously between reads.

const volatile uint32_t * const STATUS = (const volatile uint32_t *)0x40021000;
// Read-only from software, changes every time hardware updates it
while (!(*STATUS & READY_BIT)) { /* poll */ }

This is one of the most commonly asked C interview questions. Candidates who say "const and volatile are contradictory" reveal a misunderstanding of what const means in C — it means "read-only from this code's perspective," not "the value never changes."