Editing Two's complement (section)

===Working from LSB towards MSB===
A shortcut to manually convert a [[binary number]] into its two's complement is to start at the [[least significant bit]] (LSB), and copy all the zeros, working from LSB toward the most significant bit (MSB) until the first&nbsp;1 is reached; then copy that&nbsp;1, and flip all the remaining bits (Leave the MSB as a 1 if the initial number was in sign-and-magnitude representation). This shortcut allows a person to convert a number to its two's complement without first forming its ones' complement. For example: in two's complement representation, the negation of "0011&nbsp;1100" is "1100&nbsp;0<u>100</u>", where the underlined digits were unchanged by the copying operation (while the rest of the digits were flipped).

In computer circuitry, this method is no faster than the "complement and add one" method; both methods require working sequentially from right to left, propagating logic changes. The method of complementing and adding one can be sped up by a standard [[carry look-ahead adder]] circuit; the LSB towards MSB method can be sped up by a similar logic transformation.