OR gate
An OR gate’s output is 1 when any of its inputs is 1, and 0 only when all of them are 0. Its symbol has a curved back and a body that sweeps to a point.
Easily confused with
How to read it
Kuphaldt’s Lessons in Electric Circuits gives the rule: the output is high if any input is high, and low if and only if all inputs are low. Boolean algebra writes OR with a plus sign, Y = A + B: Texas Instruments gives that as the function of each gate on its SN74HC32, four 2-input OR gates on one chip, and a University at Buffalo course note writes a three-input OR as R = A+B+C. In logic the same operation is ∨, which Unicode names LOGICAL OR, also called vee or disjunction.
Also searched as: ≥1, A+B, logical OR, OR gate symbol, OR gate truth table.
Truth table
| A | B | Y = A + B |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 1 |
| 1 | 0 | 1 |
| 1 | 1 | 1 |
The two standard shapes
Distinctive shape ANSI/IEEE Std 91: curved back, pointed front. Rectangular shape IEC 60617-12: a box marked ≥1.
The rectangular form is a box marked ≥1. Texas Instruments’ guide to IEEE Std 91 says the symbol was chosen to show that at least one active input is needed to activate the output. The sign is the greater-than-or-equal sign followed by 1.
Look-alikes
The XOR gate has a second curved line behind the back, and its output is 0 when both inputs are 1. A NOR gate is the OR shape with a small circle at the output.
Read next
- Next in Logic gate symbolsNOT gate (inverter)A NOT gate, or inverter, outputs the opposite of its input: 1 becomes 0 and 0 becomes 1. Its symbol is a triangle with a small circle at its tip.
- In Logic symbolsOr symbol (∨)∨ means “or” in logic. p ∨ q, read “p or q”, is a disjunction: it is true when p is true, when q is true, or when both are.
More logic gate symbols
The same shape elsewhere
Browse symbols drawn with curves and waves or lines.
Sources
- Lessons In Electric Circuits, Volume IV: Digital, chapter 3, Logic Gates, Tony R. Kuphaldt, open textbook (Design Science License), Tony R. Kuphaldt (ibiblio), Multiple-input gates: The OR gate
- Overview of IEEE Standard 91-1984: Explanation of Logic Symbols, SDYZ001A, 1996, Texas Instruments, Table 1, General qualifying symbols
- SNx4HC32 Quadruple 2-Input OR Gates (data sheet), SN74HC32 data sheet, Texas Instruments, 3 Description
- Interpreting Logic Gates (CSE111 lecture notes), H. Kershner, Spring 2009, University at Buffalo, Department of Computer Science and Engineering, The OR gate
- Mathematical Operators, Range: 2200–22FF (code chart), The Unicode Standard, Unicode Consortium, U+2228
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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