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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. Note that terminology varies, so you will eventually see references using these terms different than presented here.

    In the case of a logical Boolean OR, the result is a logical BOOLEAN type of either TRUE or FALSE. Some languages, such as C, do not have a built-in Boolean type. There are several different and incompatible encodings for TRUE and FALSE (see table below).

    In the case of an integer Boolean OR, the OR is performed on the two integers as whole numbers. The result can be inaccurate if the integer is not in a specified form (the legal options usually being [ZERO and ONE] or [ZERO and NEGATIVE ONE]. This works best with -1 and 0 as TURE and FALSE (or vice versa). There are several different and incompatible encodings for TRUE and FALSE (see table below).

some languages		TRUE		FALSE
C		1		0
C		non-zero		zero
		negative		zero or positive
		-1		0
		0		1

    in the case of a bit-wise Boolean OR, a logical OR is performed on each corresponding bit of the two bit strings (or two single bits).

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.

OR functions

    Some languages have an OR function.

LISP    OR(x) — LISP predicate function that takes zero or more arguments of type NIL or nonNIL and returns either NIL or nonNIL. Arguments are evalutaed left to right. Evaluation stops at the first nonNIL and remaining arguments are not evaluated, returning the nonNIL argument. If the function evaluates all of the arguments and finds only NIl values, then it returns NIL.

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