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cbit

Clearing least significant bit

Question

How would I change the least significant bit to 0 without affecting the rest of the value, for example: 0xffffffff , for example in C or Python? I am not a mathematical genius, so for me it's a hassle to find out how to achieve this.

Solution

n = 0 // clear this bit
0xffffffff &= ~(1U << n) = 0xfffffffe
Solution

  • Try this to clear the least significant bit:

    int x = 0xffffffff;

...

/* clear least significant bit */
x &= ~1;

    To set the LSB

    int x = 0xffffffff;

...

/* set least significant bit */
x |= 1;

    To change the LSB

    int x = 0xffffffff;

...

/* change least significant bit */
x ^= 1;

    If you want to extent that to set / clear / change bit n, change the 1 to (1U<<n).