1-17
Q14.
Subtraction of Binary Numbers
Now that you are familiar with the addition of binary numbers, subtraction will be easy. The
following are the four rules that you must observe when subtracting:
Rule 1: 02 – 02 = 02
Rule 2: 12 – 02 = 12
Rule 3: 02 – 12 = 12
Rule 4: 12 – 12 = 12
with a borrow
The following example (101102 - 1100
2) demonstrates the four rules of binary subtraction:
Rule 4 presents a different situation because you cannot subtract 1 from 0. Since you cannot subtract
1 from 0 and have a positive difference, you must borrow the 1 from the next higher order column of the
minuend. The borrow may be indicated as shown below:
