# iGCSE Computer Science - Distance Learning

# Adding Binary Numbers (2023 Specification Only)

**New 2023 Syllabus Only**

Adding binary numbers uses the concept of long addition that you should already be familiar with from maths. There are just four rules that you need to remember:

0 + 0 = 0 (zero) 0 + 1 = 1 (one) 1 + 1 = 10 (two) 1 + 1 + 1 = 11 (three)

**Task: **As you complete this lesson, create notes using the Scribbl.it file below. These work best when printed and completed by hand – adding notes in colour will help you to remember the key terms.

### How To Add Binary Numbers

Adding binary numbers requires us to remember four rules and that we’re actually only adding denary numbers:

0 + 0 = 0

1 + 0 = 1

1 + 1 = 2 (or 10 in binary)

1 + 1 + 1 = 3 (or 11 in binary)

These first two rules are nice & simple because when you write out a binary number, there’s no need to carry a 1. When we get to the second two rules, we apply the same techniques that we use in long addition in maths.

### How Computers Deal With Overflow

When the result of a binary addition ends up with a number that has more bits than the numbers being added, this is called an overflow error. In the video, I highlighted this by drawing a box around the number and crossing it through. This technique is called signposting and helps you to tell the examiner your thought processes (*it’s like shouting at them “Give Me The Marks!!”*).

**Task**

** **Once you have completed the video lesson at the top of the page, download this practice sheet and test your understanding of adding Binary numbers. *Use the second page to check your answers.*