Lesson Objectives

1. Lesson Objectives • To understand how to add 4 and 8 bit binary numbers together • To understand what is meant by the term “Overflow” • ALL students will add 4 bit binary numbers successfully • MOST students will add 8 bit binary numbers successfully • SOME students will be able to discuss why overflow errors occur

2. Adding Denary Numbers + 2 8 1 7 1 Carryover What are the steps that we do to add 2 denary numbers together?

3. Adding Binary numbers 1+1 = 2 In binary this is 10 0+1 = 1 1+0 = 1 + 1 0 1 1 1 Carryover 0+0+1=1 We do it in exactly the same way

4. Always convert it back to denary to check the answer 8 4 2 1 5+ 6 11 + 1 0 1 1 1 Carryover

5. Task 1: When carrying over 1+1+1 = 3 = 11 Have a go at the additions in your book. Remember that in binary 0+0=0 1+0=1 0+1=1 1+1=2=10

6. Overflow Errors • Sometimes we run into problems. • Suppose we have eight bits in each location. • When we add the binary equivalent of denary 150 + 145: • There is no room for a carry so it is lost and we get the wrong answer, 39 instead of 295. • When there isn’t enough room for a result, this is called overflow and produces an overflow error. Remember the maximum 8 bit binary number 255

7. On the front of your booklets Write down the definitions for Overflow Error

8. How did you do? A/A* - 8/8 8 bit correct B – 6/7 8 bit correct C – 4/5 8 bit correct D - 6/6 4 bit numbers

9. Plenary https://www.youtube.com/watch?v=OCYZTg3jahU

10. In pairs Count up the binary numbers using your fingers to represent the digits. Test each other –