NASM:

You are to read in a 32 bit value in hexadecimal (base-16). Numbering the bits from 0 (LSB, or rightmost bit) to 31 (MSB, or leftmost bit) you are to compute three results for this number: 1. The position of the least significant 1 bit set; 2. The position of the most significant 1 bit set; 3. The total number of 1 bits set.

For example, for the constant 00fffff0h, the LSB set is 4, the MSB set is 23, and there are 20 bits set total.