Components of a machine instruction

A machine instruction is made up of a certain number of bits broken down into fields corresponding to the different information to be transmitted to the hardware:

• an operation code field. The bit pattern specifies what the instruction does. There may be a direct correspondence between the code contained in this field and an instruction, or the code may correspond to an instruction class, in which case the instruction is specified by an operation code extension field;

• one or more fields specify how to access the data on which operations are performed. The data may be contained in registers or in memory. Some fields can specify register numbers directly. For data located in memory, a...