1. Teaching Computing to GCSE Level with Python Session 3

2. Your second starter! 1. Convert these binary numbers to denary: 0 1 0 1 0 0 1 01 0 1 1 0 1 1 0 2. Convert the same numbers to hex 3. Convert these hex numbers to binary A 34 F2 42 9 4. Convert these binary numbers to hex 0 1 1 1 0 0 0 11 0 1 1 0 1 0 1 5. What is the largest denary number you can express in 9 bits? 6. How many different values can you show using 9 bits?

3. Topics for today  Theory  Binary logic: AND, OR, NOT  Truth tables  Logic Gates  www.logic.ly www.logic.ly  Programming  IF Statements

4. Binary logic  GCSE Computing link to specification  Recap on binary numbers  AND OR NOT  Truth tables  Logic diagrams  Logic.ly

5. Link to specification (OCR GCSE Computing Specification) Candidates should be able to: (d) explain why data is represented in computer systems in binary form (e) understand and produce simple logic diagrams using the operations NOT, AND and OR (f) produce a truth table from a given logic diagram. (a, b and c are points that relate to the CPU)

6. AND OR NOT  For A AND B to be true, then A must be true and B must be true  For example,  “It is true that Cambridge United won last week and there was 5 cm of snow on Friday” is only true if both are true.  For A OR B to be true then at least one of A and B must be true  “It is true that Cambridge United won last week OR there was 5 cm of snow on Friday” is true if only one of the individual statements is true  NOT A is always the opposite of A. So if A is true, NOT A is false.  For example, “It is not raining” is true if “It is raining” is false

7. The NOT gate (inverter)  Note there is 1 input, A, and 1 output (often called Q)  We can also represent this mathematically as Diagrammatic representation of a NOT gate A the bar notation represents logical NOT A

8. The AND gate  Note there are 2 inputs, A and B, and 1 output Q  We can also represent this mathematically as A. B (the dot notation represents logical AND) Diagrammatic representation of an AND gate

9. The OR gate  Note there are 2 inputs, A and B, and 1 output Q  We can also represent this mathematically as A + B (the + notation represents logical OR) Diagrammatic representation of an OR gate

10. Truth Tables  A truth table shows the output values for all the different input combinations.

11. Task  Complete the truth tables on the sheet  As a minimum, do AND, NOT and OR  Extension – try the remaining ones

12. Using Logic.Ly  Go to http://logic.ly/ and select Try Onlinehttp://logic.ly/  Close the demo box offered  Drag the gates and inputs and outputs to the main window  Try to build and AND, NOT and an OR circuit

13. Try these circuits: Circuit 1

14. Circuit 1 0 1 1 1 1 0 0 0

15. Circuit 2

16. 0 0 0 1 1 1 1 0

17. Circuit 3

18. 0 1 1 1 1 0 1 0 0 0 1 0

19. Circuit 4 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 1 1 1 1

20. Circuit 5 1 1 0 0 1 1 0 0 0 0 0 0 0 0 1 1 1 1 0 1 1 1 0 1 1 1 0 1 1 1 1 1 0 0 1 0 0 0 0 0

21. Circuit 6 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 1 1 0 0 1 1 0 0 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 0 0 1 0 0 0 1 1 1 1 0 1 1 1 0 0 0