Logic gates
Cambridge IGCSE Computer Science (0478) · Unit 3: Hardware · 10 flashcards
Logic gates is topic 3.4 in the Cambridge IGCSE Computer Science (0478) syllabus , positioned in Unit 3 — Hardware , alongside Computer architecture, Input and output devices and Memory and storage. In one line: An OR gate outputs '1' (TRUE) if at least one of its inputs is '1' (TRUE). It only outputs '0' (FALSE) if all inputs are '0' (FALSE).
This topic is examined in Paper 1 (computer systems theory) and Paper 2 (algorithms, programming and logic).
The deck below contains 10 flashcards — 5 definitions and 5 key concepts — covering the precise wording mark schemes reward. Use the 5 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
Describe the function of an OR gate
An OR gate outputs '1' (TRUE) if at least one of its inputs is '1' (TRUE). It only outputs '0' (FALSE) if all inputs are '0' (FALSE).
What the Cambridge 0478 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- Understand Understand that a computer needs a network interface card (NIC) to access a network
- Understand Understand what is meant by and the purpose of a media access control (MAC) address, including its structure
- Understand Understand what is meant by and the purpose of an internet protocol (IP) address
- Understand Understand that there are different types of IP address including IPv4 and IPv6
- Describe Describe the role of a router in a network
Draw the truth table for an AND gate.
An AND gate outputs '1' (TRUE) only if both inputs are '1' (TRUE). Otherwise, the output is '0' (FALSE). The truth table has input columns A and B, and output column Q, with rows: 0 0 0, 0 1 0, 1 0 0, 1 1 1.
Describe the function of an OR gate.
An OR gate outputs '1' (TRUE) if at least one of its inputs is '1' (TRUE). It only outputs '0' (FALSE) if all inputs are '0' (FALSE).
What logic gate is represented by the Boolean expression Q = NOT A?
The Boolean expression Q = NOT A represents a NOT gate. The NOT gate inverts the input; if A is '1', Q is '0', and vice-versa.
Draw the logic gate symbol for a NAND gate.
A NAND gate symbol is an AND gate symbol followed by a small circle (inversion bubble) at the output. The circle represents the NOT operation.
Explain the difference between a NOR gate and an OR gate.
A NOR gate is the inverse of an OR gate. Where an OR gate outputs '1' if any input is '1', a NOR gate outputs '1' only if *all* inputs are '0'.
Create the truth table for a NOT gate.
A NOT gate takes a single input and inverts it. If the input (A) is '0' (FALSE), the output (Q) is '1' (TRUE). If the input is '1' (TRUE), the output is '0' (FALSE). Truth table has two rows: 0 1, 1 0
Define the term 'logic gate'.
A logic gate is an elementary building block of a digital circuit. It takes one or more binary inputs (0 or 1) and produces a single binary output based on a logical operation.
What is a 'truth table' used for in the context of logic gates?
A truth table is a table that shows all possible combinations of inputs to a logic gate (or circuit) and the corresponding output for each combination. It completely defines the behavior of the gate.
Write the Boolean expression for a NOR gate with inputs A and B and output Q.
The Boolean expression for a NOR gate with inputs A and B and output Q is: Q = NOT (A OR B).
Describe how a logic circuit can be created from logic gates.
A logic circuit is formed by connecting multiple logic gates together, where the output of one or more gates can be used as the input to other gates, implementing more complex logical functions.
Key Questions: Logic gates
Describe the function of an OR gate.
An OR gate outputs '1' (TRUE) if at least one of its inputs is '1' (TRUE). It only outputs '0' (FALSE) if all inputs are '0' (FALSE).
Explain the difference between a NOR gate and an OR gate.
A NOR gate is the inverse of an OR gate. Where an OR gate outputs '1' if any input is '1', a NOR gate outputs '1' only if *all* inputs are '0'.
Define the term 'logic gate'.
A logic gate is an elementary building block of a digital circuit. It takes one or more binary inputs (0 or 1) and produces a single binary output based on a logical operation.
What is a 'truth table' used for in the context of logic gates?
A truth table is a table that shows all possible combinations of inputs to a logic gate (or circuit) and the corresponding output for each combination. It completely defines the behavior of the gate.
Describe how a logic circuit can be created from logic gates.
A logic circuit is formed by connecting multiple logic gates together, where the output of one or more gates can be used as the input to other gates, implementing more complex logical functions.
More topics in Unit 3 — Hardware
Logic gates sits alongside these Computer Science decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 0478 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Key terms covered in this Logic gates deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Logic gates deck
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