How do I set one bit in C?

Apply x |= (1u << n). The other bits keep their value.

How do I clear one bit in C?

Apply x &= ~(1u << n). The NOT builds a mask with a single 0.

The operator & works on every bit and gives an integer. The operator && gives 0 or 1 and stops at the first false operand.

Apply x |= (1u << n). The other bits keep their value.

Apply x &= ~(1u << n). The NOT builds a mask with a single 0.

The operator & works on every bit and gives an integer. The operator && gives 0 or 1 and stops at the first false operand.

C has six bitwise operators: AND, OR, XOR, NOT and the two shifts.

Each one works on every bit of an integer type.

The logical operators && and || are different operators with different results.

The mask 1 << 3, which is bit 3. Edit the expression or select a bit to flip it.

Expression

value · 8 bits · unsigned

Shift

The bitwise operators of C and C++
Operator	Name	Idiom	Effect
&	AND	x & mask	Keep the bits of the mask
\|	OR	x \|= mask	Set the bits of the mask
^	XOR	x ^= mask	Toggle the bits of the mask
~	NOT	x & ~mask	Clear the bits of the mask
<<	Left shift	1u << n	Build a mask for bit n
>>	Right shift	x >> n	Move bit n down to bit 0
&	Test	if (x & mask)	True when a bit of the mask has the value 1

A register of a microcontroller needs these operators for every field.

A flag word packs many boolean values into one integer.

An embedded codebase uses these idioms more than it uses arithmetic.

C leaves a shift of a signed negative value undefined. Shift an unsigned type.
C leaves a shift by the width of the type or more undefined. A shift of a 32-bit value by 32 is not 0.
The right shift of a signed negative value keeps the sign on most targets, so it does not divide as expected.
Write 1u << 31 rather than 1 << 31. The literal 1 is a signed int, and the shift overflows it.
The operator & has lower precedence than ==, so write (x & mask) != 0 with the parentheses.

The full editor holds many values, evaluates expressions across them, and reads live values from a serial port.

How do I set one bit in C?: Apply x |= (1u << n). The other bits keep their value.
How do I clear one bit in C?: Apply x &= ~(1u << n). The NOT builds a mask with a single 0.
What is the difference between & and &&?: The operator & works on every bit and gives an integer. The operator && gives 0 or 1 and stops at the first false operand.