Combining Boolean Operators (AQA GCSE Computer Science)
Revision Note
Combining Boolean Operators
Boolean operators can be combined to produce more complex expressions
The combination of two or more Boolean operators forms a logic expression
Brackets are used to clarify the order of operations
A logic diagram is a visual representation of combinations of Boolean operators within a logic circuit
An example would be Q = NOT(A OR B) //
In the diagram above, the inputs are represented by A and B
P is the output of the OR gate on the left and becomes the input of the NOT gate
Q is the final output of the logic circuit
This is a logic diagram for the Boolean expression Q = NOT(A OR B) //
Examiner Tip
You may be asked to draw a logic circuit from a logic statement or a Boolean expression OR write the logical expression that is expressed in the logic diagram using Boolean expression operators
Logic circuits will be limited to a maximum of three inputs and one output
Example of combining Boolean operators
P = (A OR B) AND NOT C //
Worked Example
A green light (G) in a game switches on if all of the following conditions are true:
sensor D is off
sensor L is off
sensor W is on
Write a Boolean expression for this logic circuit.
You must use Boolean expression operators in your answer [3]
Answer
D̅. L̅. W // (D̅. W). (L̅. W)
Guidance
2 marks if fully correct but using different notation, e.g. NOT D AND NOT L AND W
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