Exclusive or is a logical operation that returns true only if one operand is true and the other is false. For propositions a and b, exclusive or is true if either a or b are true, but not both. Table 1 is the truth table for exclusive or. Exclusive or can also be called an exclusive disjunction. When writing, the term 'exclusive or' is sometimes abbreviated as 'xor'; which is pronounced 'ex-or'.
Three ways in which exclusive or can be written are: . In many programming languages, exclusive or is denoted with the caret symbol (^). In electronics, an exclusive or gate is drawn as:Figure 1: Venn diagram of A xor B. |
Property Using Words | Property Using Symbols | Description |
---|---|---|
a xor false = a | a⊕false = a | |
a xor true = not a | a⊕true = ¬a | |
a xor a = false | a⊕a = false | The definition of exclusive or implies that if both operands are true, or both operands are false, then exclusive or returns false. a≠a, a xor a must always be false. |
a xor not a = true | a⊕¬a = true | The definition of exclusive or states that if the two operands are not equal, exclusive or returns true. Since a?not a, a xor not a is always true. |
a xor b = b xor a | a⊕b = b⊕a | Exclusive or is commutative. |
a xor (b xor c) = (a xor b) xor c | a⊕(b⊕c) = (a⊕b)⊕c | Exclusive or is associative. |
a xor b = not a xor not b | a⊕b = ¬a⊕¬b | If the truth value of both operands are swapped, exclusive or still returns the same value. |
not (a xor b) = not a xor b = a xor not b | ¬(a⊕b) = ¬a⊕b = a⊕¬b | The logical negation of exclusive or result is the same thing as negating one of the operands of the exclusive or. |
a xor b = (a and not b) or (not a and b) | a⊕b = (a∧¬b)∨(¬a∧b) | This is a restatement of the definition of exclusive or: an exclusive or operation is true only if one of the arguments is true and the other is false. |
a xor b = (a or b) and (not a or not b) | a⊕b = (a∨b)∧(¬a∨¬b) | This is again a restatement of the definition of exclusive or. The first term (a or b) is true if either a or b is true. The second term (not a or not b) is true if either a and b is false. With the conjunction, the entire expression is true if either a or b is true. |
a xor b = (a or b) and not (a and b) | a⊕b = (a∨b)∧¬(a∧b) | This is another restatement of the definition of exclusive or. |
Table 2: Properties of Exclusive Or. |
In logic, the operands of exclusive or must be a truth value, must be either true of false. In computers, the operands of exclusive or are binary numbers. The exclusive or is applied to corresponding bits of the operands: .
# | A | B | C | D |
E | F | G | H | I |
J | K | L | M | N |
O | P | Q | R | S |
T | U | V | W | Y |
Z | X |
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