Computing 2's complement in Excel

Question

How can I compute the 2s complement of a binary number in Excel. Which Excel functions do I need?

For example, if I have the binary sequence 11101010, the 2s complement can be obtained as,

1. Replace all 1's with 0's and 0's with 1's: 00010101
2. add 1 to the result of step 1: 00010110

An excel implementation of the above is what I need.

Answer 1

Remember that Two's complement was invented as a way to to a subtraction in a computer to represent negative numbers, so this problem can be solved as a simple subtraction, so get the complement and then add one.

=DEC2BIN(255 - BIN2DEC(A1) + 1)

Where A1 is a cell with a binary number as text. If you want to use a bigger number then use the biggest number that can be represented by the number of bits that you want to use, here my example is for 8 bits, so (2^8)-1 = 255