Instruction

In computer science, an instruction is a single operation of a processor defined by an instruction set architecture. In a broader sense, an "instruction" may be any representation of an element of an executable program, such as a bytecode.
On traditional architectures, an instruction includes an opcode specifying the operation to be performed, such as "add contents of memory to register", and zero or more operand specifiers, which may specify registers, memory locations, or literal data. The operand specifiers may have addressing modes determining their meaning or may be in fixed fields.