The commonly used format of an instruction in assembly language is given below:
Memory Address This is the address of the memory location in which a program or a series of instructions are stored.
Machine Codes Every instruction has a unique one-byte code called operation code. Instructions are operated using data. Data may be of one byte or two bytes. Machine codes are the hexadecimal representation of operation codes.
Labels It is assigned for the instruction in which it appears. The presence of a label in an instruction is optional. When a label is present, it provides a symbolic name that can be used in branch instructions of the instruction. If there is no label, then the colon must not be entered. A label may be of any length, from 1 to 35 characters. This appears in a program to identify the name of a memory location for storing data and other purposes. This is used for conditional/unconditional jumping.
Mnemonics Each instruction has a specific mnemonic. The mnemonic states the operation which will be executed.
Operands Operands depend on the type of instruction. In a one-byte instruction, there is no operand. Only one operand exists in two-byte instructions and a three-byte instruction has two operands which are separated by a comma.
Comments In this field, the general comments about the instructions are always incorporated to understand the program easily. It is optional. The comment field contains any combination of characters. A comment may appear on a line and the first character of the line must be a semicolon.