Ones complement of 010101 – UGC NET Question

The 1's complement of a binary number is obtained by inverting each bit, changing 0 to 1 and 1 to 0. For 010101, flipping each bit produces 101010. This new pattern is the 1's complement and reflects bitwise inversion of the original number.

Option A:
Option A repeats the original pattern without any inversion. Since 1's complement requires changing each bit, leaving the number unchanged cannot be correct.

Option B:
Option B, 010110, differs from the original in only one bit, which is insufficient for a full complement. 1's complement must invert all bits, not just some.

Option C:
Option C is correct because it flips 0→1 and 1→0 at every position, giving 101010 from 010101. This is the precise definition of 1's complement and is used in some earlier signed number representations.

Option D:
Option D, 101101, changes several bits but not in a simple inversion pattern. Some positions do not reflect the opposite of the original bits, so it is not a valid 1's complement.