The tilde operator in C

The ~ operator is bitwise NOT, it inverts the bits in a binary number:

NOT 011100
  = 100011

~ is the bitwise NOT operator. It inverts the bits of the operand.

For example, if you have:

char b = 0xF0;  /* Bits are 11110000 */
char c = ~b;    /* Bits are 00001111 */