Volatile Objects and Absolute Variables

The Compiler does not do register- and constant tracing on volatile or absolute global objects. Accesses to volatile or absolute global objects are not eliminated. See the following listing for one reason to use a volatile declaration.

Listing: Using volatile to avoid an adverse side effect

volatile int x; 
void main(void) { 
 x = 0; 
 ... 
 if (x == 0) { // without volatile attribute, the 
 // comparison may be optimized away! 
 Error(); // Error() is called without compare! 
 } 
}