How do you set, clear, and toggle a specific bit in C?

Set with OR (flags |= 1<<n), clear with AND-NOT (flags &= ~(1<<n)), and toggle with XOR (flags ^= 1<<n).

#define BIT(n) (1 << (n))

// SET bit n (force to 1)
flags |= BIT(n);
flags |= (1 << n);

// CLEAR bit n (force to 0)
flags &= ~BIT(n);
flags &= ~(1 << n);

// TOGGLE bit n (flip 0↔1)
flags ^= BIT(n);
flags ^= (1 << n);

Example with bit 2:

// 00000001
unsigned char flags = 0x01;

// SET:    00000101 (0x05)
flags |= (1 << 2);
// CLEAR:  00000001 (0x01)
flags &= ~(1 << 2);
// TOGGLE: 00000101 (0x05)
flags ^= (1 << 2);
// TOGGLE: 00000001 (0x01)
flags ^= (1 << 2);

Why these work:

• x | 1 = 1 (OR with 1 always gives 1)
• x & 0 = 0 (AND with 0 always gives 0)
• x ^ 1 = ~x (XOR with 1 flips the bit)