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Boolean OR

summary

    This subchapter looks at Boolean OR.

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Boolean OR

    This subchapter looks at Boolean OR.

    Please note the differences between a logical Boolean operation, an integer Boolean operation, and a bit-wise Boolean operation.

OR

    OR (or inclusive or) requires either object to be true for the result to be true. The OR works like a pair of switches in parallel. Current will flow if either or both switches are closed.

    OR is conisdered to be Boolean addition and is represented by the plus symbol: + (such as (A+B). There is no Boolean subtraction operation.

    The truth table for OR is as follows:

OR

A	B	result
0	0	0
1	0	1
0	1	1
1	1	1

    The OR gate in logic circuits looks like:

    The OR operation has a result of 1 when any of its input variables is 1.

    The OR operation has a result of 0 only when both of its input variables are 0.

    In OR (Boolean addition) 1 + 1 = 1. Similarly, 1 + 1 + 1 = 1.

functions

PL/I    ANY(x) — Pl/I built-in function that performs a Boolean OR on all of the bits of the bit string x. If the data item x is not a bit string, then it is converted to a bit string. If the data item x is CHARACTER then the character string should contain only the characters '1' and '0'. If the data item x is arithmetic, then the item is changed into a positive fixed point binary integer (applying absolute value if needed) and the OR operation is performed on the bits of the integer ignoring the plus sign. The result returned is '1'B if any bit is '1'B and the result returned is '0'B if none of the bits are a '1'B.

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.

• OR Inclusive Or Logical; Motorola 680x0, Motorola 68300; performs a logical inclusive OR 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
• ORI Inclusive Or Immediate; Motorola 680x0, Motorola 68300; performs a logical inclusive OR of the contents of a register or memory location (8, 16, or 32 bits) with an immediate; sets or clears flags
• OR Logical Inclusive OR; Intel 80x86; performs a logical 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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