Opcode: Difference between revisions

Revision as of 14:48, 18 April 2007

Revision as of 03:01, 20 May 2007

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In [[computer science]], an '''opcode''' is the portion of a [[machine language]] [[instruction (computer science)|instruction]] that specifies the operation to be performed. The term is an abbreviation of '''Op'''eration '''Code'''. Their specification and format will be laid out in the [[instruction set architecture]] (ISA) of the [[computer hardware]] component in question—normally a [[central processing unit|CPU]], but possibly a more specialized unit. A complete machine language instruction contains an opcode and, optionally, the specification of one or more [[operand]]s—what data the operation should act upon. Some operations have ''implicit'' operands, or indeed none. Some ISAs have instructions with defined fields for opcodes and operands, while others (e.g. the [[Intel x86]] architecture) have a more complicated and ad-hoc structure.

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== See also ==

* [[Illegal opcode]]

==References==

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*[http://www.computer-glossary.net/definition/5004-OPCODE definition of: OPCODE] at computer-glossary.net

[[Category:Machine code]]