Boolean Logic

What Boolean Logic covers

Boolean Logic is examined in J277/02, Computational thinking, algorithms and programming. It covers logic gates and truth tables and Combining gates in logic diagrams.

The 2 subtopics

Each one has its own page.

• Logic gates and truth tablesAND, OR and NOT gates and their symbols, truth tables for up to three inputs, conjunction, disjunction and negation, and gates applied to everyday problems.Open →
• Combining gates in logic diagramsTurning logic diagrams into Boolean expressions and back, worked outputs for combined gates, truth tables for expressions, and designing circuits for alarms and heaters.Open →

What you need to know

Answer each one before you reveal it.

Take Boolean Logic further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• AND gate vs OR gate

  AND gate: a component whose output is 1 only when every input is 1. OR gate: a component whose output is 1 when at least one input is 1.

• Conjunction vs Disjunction

  Conjunction: the logical operation written as AND. Disjunction: the logical operation written as OR.

• Truth table vs Logic diagram

  Truth table: a grid listing every combination of inputs with the output each gives. Logic diagram: a drawing of connected gate symbols showing how inputs pass to an output.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is a logic gate?

   Model answer

   A logic gate is a component that applies a Boolean operation to one or more binary inputs. A gate gives a single output of 1 or 0.

2. 2

   What does an AND gate do?

   Model answer

   An AND gate outputs 1 only when both of its inputs are 1. Every other combination of inputs gives 0.

3. 3

   What does an OR gate do?

   Model answer

   An OR gate outputs 1 when at least one of its inputs is 1. The output is 0 only when both inputs are 0.

4. 4

   Describe what a NOT gate does.

   Model answer

   A NOT gate takes a single input and outputs the opposite value. An input of 1 gives 0, and an input of 0 gives 1.

5. 5

   How many of the four rows in the truth table for A OR B have an output of 1?

   Model answer

   Three of the four rows output 1. Only the row where A and B are both 0 outputs 0.

6. 6

   What are conjunction, disjunction and negation?

   Model answer

   Conjunction is another name for AND, and disjunction is another name for OR. Negation is another name for NOT.

What is inside Levo

Six ways to work the same material.

Boolean Logic revision questions

What does Boolean Logic cover in OCR GCSE Computer Science?

2 subtopics: logic gates and truth tables and combining gates in logic diagrams. Each one has its own page with questions and model answers.

How is Boolean Logic organised?

By the OCR J277 specification, subtopic by subtopic, so it matches the order you are taught it in.