A processor executes instructions. An instruction is composed of an operation and zero or more operands.

| operator | operand |

In the case of a binary cpu, an instruction is composed of bits (  -> BinaryDigit   ).
The complete instruction is read by the cpu as a string of bits. The length of the string is dependant on the architecture of the cpu. A cpu is characterised by the bit-length of its instruction.

For example a cpu that uses an  -> InstructionSet  
instruction length of 8 bits is a 8-bit cpu.

The instruction is encoded in the string as a sequence, or string, of zeros and ones. In the case of an 8 bit instruction:

| x | x | x | x | x | x | x | x |

where the x is either a 0 or 1.

Since an instruction operates on something, the instruction is composed of an operator and an operand in the same string of bits. Thus there is an operator-part and an operand-part in the string of bits.

Again dependant on the architecture of the cpu varies the length of these parts in the string.

Lets asume the cpu consits of operators encoded with a length of 3 bits,

| O | O | O | A | A | A | A | A |

where the O represents an operator-bit, and the A represents an operand-bit ( A for operand, since an operand is also named an argument).

Now the opcode is:

| O | O | O |