C Bitwise Operations Cheat Sheet

Operations Table

Operation	Sample	C Operator
AND	1001 AND 0101 = 0001	& (ampersand)
OR	1001 OR 0101 = 1101	| (pipe)
NOT	NOT 1001 = 0110	~ (tilde)
XOR	1001 XOR 1011 = 0010	^ (caret)
LEFT-SHIFT	LEFT-SHIFT 0001 BY 1 = 0010	<<
RIGHT-SHIFT	RIGHT-SHIFT 1000 BY 1 = 0100	>>

C Assignment Operators

Operation	Syntax	Short For
AND	X &= Y;	X = X & Y;
OR	X |= Y;	X = X | Y;
XOR	X ^= Y;	X = X ^ Y;
LEFT-SHIFT	X <<= Y;	X = X << Y;
RIGHT-SHIFT	X >>= Y;	X = X >> Y;

Setting and Checking Bit-Flags

#include <stdlib.h>
#define FLAG_ONE 0x0001     /* 0001 */
#define FLAG_TWO 0x0002     /* 0010 */
#define FLAG_THREE 0x0004   /* 0100 */

int main(void)
{
  unsigned int Flags = 0x0000; /* Initialize to zero */
  Flags |= FLAG_ONE;           /* Flags now contains 0001 */
  Flags |= FLAG_THREE;         /* Flags now contains 0101 */

  /* will return EXIT_SUCCESS since we never set FLAG_TWO: */
  return (Flags & FLAG_TWO) ? EXIT_FAILURE : EXIT_SUCCESS;

Counting Set Bits

#include <stdlib.h>
#include <stdio.h>
#define BITS_PER_INT ( sizeof(unsigned int) * 8 )
 
int main(void)
{
  unsigned int Flags = 0x0115; /* Dec: 277, Bin: 100010101 */
  unsigned int Mask = 0x0001;
  unsigned int Count = 0;
  unsigned int i = 0;

  for (i = 0; i < BITS_PER_INT; ++i, Mask <<= 1)
    if (Flags & Mask)
      ++Count;

  // The following line should print: Flags contains 4 set bits.
  printf("Flags contains %d set bits.\n", Count);
  return EXIT_SUCCESS;
}