Teaching Computing to GCSE Level with Python

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 0 1 0 1 1 0 1 1 0 2. Convert the same numbers to hex 3. Convert these hex numbers to binary A 3 4 F 2 4 2 9 4. Convert these binary numbers to hex 0 1 1 1 0 0 0 1 1 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 • 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. A A The NOT gate (inverter) Diagrammatic representation of a NOT gate • Note there is 1 input, A, and 1 output (often called Q) • We can also represent this mathematically as the bar notation represents logical NOT

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

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

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 Online • 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. 0 1 1 0 1 0 1 0 Circuit 1

15. Circuit 2

16. 0 1 0 1 0 1 1 0 Circuit 2

17. Circuit 3

18. 0 1 0 1 0 0 1 1 1 1 0 0 Circuit 3

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

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

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