Volatile identifier in C

• Used for variables
• To avoid compiler optimization
• Used for memory mapped IO

Compiler Optimization (Example)

static int val;

void func1() {

val = 0;

while (val != 0xff) // optimize as while(1)

;

}

void func2() {

val = 0;

while (*(volatile int *) &val != 0xff) // no optimization applied

;

}