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In boolean logic, logical nor or joint denial is a truth-functional operator which produces a result that is the negation of logical or. That is, a sentence of the form (''p'' NOR ''q'') is true precisely when neither ''p'' nor ''q'' is true—i.e. when both of ''p'' and ''q'' are ''false''. In grammar, nor is a coordinating conjunction. The NOR operator is also known as Peirce's arrow — Charles Sanders Peirce introduced the symbol ↓ for it, and demonstrated that the logical NOR is completely expressible: by combining uses of the logical NOR it is possible to express any logical operation on two variables. Thus, as with its dual, the NAND operator (a.k.a. the Sheffer stroke — symbolized as either | or /), NOR can be used by itself, without any other logical operator, to constitute a logical formal system (making NOR functionally complete). It is also known as Quine's dagger (his symbol was †), the (from Greek αμφηκης, cutting both ways; compare ''amphi-'') by Peirce,〔C.S. Peirce, CP 4.264〕 or "neither-nor". One way of expressing ''p'' NOR ''q'' is , where the symbol signifies OR and the bar signifies the negation of the expression under it: in essence, simply . Other ways of expressing ''p'' NOR ''q'' are X''pq'', and . The computer used in the spacecraft that first carried humans to the moon, the Apollo Guidance Computer, was constructed entirely using NOR gates with three inputs.〔 〕 ==Definition== The NOR operation is a logical operation on two logical values, typically the values of two propositions, that produces a value of ''true'' if and only if both operands are false. In other words, it produces a value of ''false'' if and only if at least one operand is true. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Logical NOR」の詳細全文を読む スポンサード リンク
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