View source for A-level Computing/AQA/Paper 2/Fundamentals of computer systems/Boolean gate combinations

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{{DISPLAYTITLE:Fundamental Hardware Elements of Computers: Boolean gate combinations}}
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Now you have learnt logic gates we will take a look at how they are combined inside hardware.  You may well be asked in an exam to draw your own logic gates or to work out what a combination of logic gates will output.  In this section we will look at the best way to describe what a set of logic gates is in boolean algebra. Let's take a look at a quick example:

[[File:CPT-logic-gate_example.svg|350px|center]]

{{CPTExercise|title=Exercise: Logic gate combination outputs}}
{{CPTQuestion|For the following logic gate combinations work out output Q for each:}}

{{CPTQuestion|[[File:CPT-logic-gate ex1.svg]]}}
{{CPTAnswer|[[File:CPT-logic-gate ex1 Answer.svg]]}}
{{CPTQuestion|[[File:CPT-logic-gate ex2.svg]]}}
{{CPTAnswer|[[File:CPT-logic-gate ex2 - Answer.svg]]}}
{{CPTQuestion|[[File:CPT-logic-gate ex3.svg]]}}
{{CPTAnswer|[[File:CPT-logic-gate ex3 - Answer.svg]]<br/>This equation can be simplified to equal <math>A.B</math>, as <math>B . B = B</math>, we'll find out why this is the case in the [[../Simplifying boolean equations|simplifying boolean equations]] section coming up}}
{{CPTQuestion|[[File:CPT-logic-gate ex4.svg]]}}
{{CPTAnswer|[[File:CPT-logic-gate ex4 - Answers.svg]]<br/>This equation can be simplified to equal 0 (always false), as <math>\overline{A+B}.A = 0</math>, we'll find out why this is the case in the [[../Simplifying boolean equations|simplifying boolean equations]] section coming up}}
{{CPTQuestion|[[File:CPT-logic-gate ex5.svg]]}}
{{CPTAnswer|[[File:CPT-logic-gate ex5 - Answers.svg]]}}
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