
2(10) 
We can also use the borrow method to do binary subtraction. The basic rules for binary subtraction are listed in the table below.
Rule 1  Rule 2  Rule 3  Rule 4 
0  0 0 
1  1 0 
1  0 1 
0  1 1 
Again we see that the first three rules are similar to their decimal counterparts. The fourth rule, however, needs a little more explanation since it defines how we borrow from another column. Let's look at a simple example to see where this rule comes from. Consider the problem of subtracting 1_{2} from 10_{2}.

10  1 

1 01 

1 0 

10  1 1 
We can apply the rules of subtraction to solve larger subtraction problems in binary. The animation below demonstrates how to subtract the binary numbers 10101_{2} and 1110_{2}. Click on the "Start Tutorial" box to view the animation.