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Boolean Exclusive OR (XOR)
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This subchapter looks at Boolean exclusive OR (XOR).
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Boolean Exclusive OR (XOR)
This subchapter looks at Boolean exclsuive OR (XOR).
XOR
XOR (or exclusive or) is similar to the normal English meaning of the word “or” — a choice between two items, but not both or none. XOR is less commonly written EOR. The symbol for the XOR operation is 
.
The truth table for XOR (exclusive OR) is as follows:
| A | B | result |
|---|---|---|
| 0 | 0 | 0 |
| 1 | 0 | 1 |
| 0 | 1 | 1 |
| 1 | 1 | 0 |
The XOR gate in logic circuits looks like:
XOR is not considered to be a basic Boolean operation, but is widely used in logic expressions. XOR is the same as ( (A) · (¬B) ) + ( (¬A) · (B ) ), extra parenthesis added for clarity.
assembly language instructions
Logical instructions typically work on a bit by bit basis, although some processors use the entire contents of the operands as whole flags (zero or not zero input, zero or negative one output). Typical logical operations include logical negation or logical complement (NOT), logical and (AND), logical inclusive or (OR or IOR), and logical exclusive or (XOR or EOR). Logical tests are a comparison of a value to a bit string (or operand treated as a bit string) of all zeros. Some processors have an instruction that sets or clears a bit or byte in registers or memory based on the processor condition codes.
- XOR Exclusive OR; DEC VAX; performs a logical exclusive OR of the bit mask (first operand, register or memory) with the source (second operand, register or memory), available in two operand (results stored in second operand) and three operand (results stored in third operand) (XORB2 exclusive or byte 2 operand, XORB3 exclusive or byte 3 operand, XORW2 exclusive or word 2 operand, XORW3 exclusive or word 3 operand, XORL2 exclusive or longword 2 operand, XORL3 exclusive or longword 3 operand); sets or clears flags
- EOR Exclusive Or Logical; Motorola 680x0, Motorola 68300; performs a logical exclusive or (XOR) of a source operand with a destination operand and stores the result in the destination operand (8, 16, or 32 bits), one of the two operands must be a data register, the other operand can be the contents of any register or memory location; sets or clears flags
- EORI Exclusive Or Immediate; Motorola 680x0, Motorola 68300; performs a logical exclusive or (XOR) of the contents of a register or memory location (8, 16, or 32 bits) with an immediate; sets or clears flags
- XOR Logical Exclusive OR; Intel 80x86; performs a logical exclusive OR between two registers, a register and contents of a memory location, or an immediate operand and either the contents of a register or the contents of a memory location; byte (8 bits), word (16 bits), or doubleword (32 bits); sets or clears flags
See also Logical Instructions in Assembly Language
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