Cambridge O Level Computer Science · Syllabus 2210 · Boolean Logic
OR Gate
What is OR Gate?
A two-input logic gate whose output is 1 when one or both inputs are 1 and 0 only when both inputs are 0; its symbol is a shield shape with a curved back and a pointed nose, and it is written X = A OR B.
This definition is part of the Boolean Logic chapter in Cambridge O Level Computer Science.
Common mistakes with OR Gate
- “OR means exactly one of the inputs is 1.”ActuallyThe OR gate is inclusive: it outputs 1 when one input is 1, and also when both are. 1 OR 1 = 1.The real gate“Exactly one” is XOR, and it is a different symbol with a different truth table.Why it happensEveryday English uses “or” exclusively — “tea or coffee” rarely means both.
Questions students ask about OR Gate
Why does NOT only ever have one input?
The syllabus defines NOT as a single-input gate, and there is no two-input NOT symbol. If a drawing shows two wires arriving at what should be a NOT, an AND or an OR gate has been left out; draw the missing gate first, then feed its single output into the NOT.
Reviewed by Academiq Edu Instructor PanelLast reviewed Syllabus 2026-2028