Teaching Computing to GCSE Level with Python Session

Teaching Computing to GCSE Level with Python Session 3

Your second starter! 1. Convert these binary numbers to denary: 01010010 10110110 2. Convert the same numbers to hex 3. Convert these hex numbers to binary A 3 4 F 24 29 4. Convert these binary numbers to hex 01110001 10110101 5. What is the largest denary number you can express in 9 bits? 6. How many different values can you show using 9 bits?

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

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

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

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

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

The AND gate Diagrammatic representation of an 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)

The OR gate Diagrammatic representation of an 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)

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

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

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

Try these circuits: Circuit 1

Circuit 1 0 1 1 0 0 0

Circuit 2

Circuit 2 0 0 0 1 1 0

Circuit 3

Circuit 3 0 1 1 0 1 0 0 0 1 0

Circuit 4 0 0 0 0 1 1 0 0 1 0 0 0 1 1 1

Circuit 5 1 0 1 1 0 0 0 1 1 0 1 0 1 1 0 0 1 1 1 0

Circuit 6 0 0 0 1 1 0 0 0 1 1 0 0 0 1 1 0 0 1 0 1 1 1 0 1 0