How do you subtract binary numbers, specifically 100102 - 11012?

To subtract binary numbers, we align them and subtract column by column, borrowing when necessary. When we borrow from a 0, we must borrow from the next available 1 to the left, turning intermediate $0$s into $1$s and the 1 we borrowed from into a 0. A borrowed 1 from the next column means we add 2 (which is $10_2$) to the current column.

We need to calculate $10010_2 - 1101_2$.

Step 1: Align the numbers.

\begin{array}{ccccc} & 1 & 0 & 0 & 1 & 0_2 \\