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Binary subtraction rules

Binary subtraction tutorial

Binary subtraction tutorial is simple.

Binary subtraction rules are similar to the decimal subtraction rules.

First of all, you have to know the binary subtraction table.

The subtraction table of binary numbers:

10 - 1 = 1
1 - 0 = 1
1 - 1 = 0
0 - 0 = 0
Here, all numbers are binary.

But there is an issue:

0 - 1 = ?

In this case the binary subtraction rule is

If you have to subtract binary 1 from binary zero borrow binary 1 from the left column.

Look at the following binary subtraction example.

Binary subtraction example

Subtract 102 from 1002:

Here, we first subtract the zero of the subtrahend from the right zero of the 100

 100
- 10
   0

Now we have to subtract the binary 1 from the binary 0. How to perform that?

To perform that we borrow the binary 1 from the left column of the 100 (the minuend)

 0(10)0
-   10
     0

The number in the parentheses is the zero with the borrowed 1.

We know from the subtraction table of binary numbers that

10 - 1 = 1

So the answer is

 0(10)0
-   10
    10

and finally

 100
- 10
  10

It is just as in the decimal system, but there are only 0 and 1 and the subtraction table at our disposal.