Explain the significance of different fields of an instruction

An instruction is a command given to a computer to perform a particular operation on some given data and the format in which the instruction is specified is called as Instruction format. The most common fields found in the instruction are:-

(i)  An operation code field that specifies the operation to be executed. It is called as opcode field.

(ii)  An address field that designates the registers address and/or a memory addresses.

(iii)  A mode field that specifies the way the operands or the efficient address is determined.