Symbol used for NOT operator.

bool b1 = true;
bool b2 = false;
char m = 0x12; // i.e. 00010010 in binary
char n = ~m;   // m will be 0xED, i.e. 11101101 in binary

// Test if b1 is true AND b2 is NOT true
if (b1 && !b2)
{
   ...
}