Why is the volatile keyword important in embedded C programming?

The volatile keyword tells the compiler that a variable's value can change unexpectedly, preventing optimization that would cache the value in a register. Use cases in embedded systems: Memory-mapped peripheral registers (hardware can change value). Variables modified in ISRs (ISR changes value asynchronously). Variables shared between tasks in RTOS. Multi-core shared memory. Without volatile: Compiler may optimize away repeated reads. Cached register value used instead of actual memory. Changes from ISR/hardware may be missed. Example: volatile uint32_t *GPIO_DATA = (uint32_t*)0x40000000; Volatile does NOT: Provide atomicity (still need critical sections). Ensure memory ordering (need memory barriers on some architectures). Replace proper synchronization mechanisms.