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Opcode
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<p>In <a href="/facts/Computing/Kghtm9fX">computing</a>, an opcode (abbreviated from operation code) is an <a href="/facts/Enumeration/EFmP9zL6">enumerated value</a> that specifies the operation to be performed. Opcodes are employed in hardware devices such as <a href="/facts/Arithmetic_logic_unit/SgIjPzSc">arithmetic logic units</a> (ALUs), <a href="/facts/Central_processing_units/Jxp1bqMV">central processing units</a> (CPUs), and software instruction sets. In ALUs, the opcode is directly applied to circuitry via an input signal bus. In contrast, in CPUs, the opcode is the portion of a <a href="/facts/Machine_code/bgdQ1Fxf">machine language</a> <a href="/facts/Instruction_(computer_science)/8p8vwUeE">instruction</a> that specifies the operation to be performed. </p>