The document discusses instruction formats in the 8086 microprocessor, highlighting their significance in assembly language programming. It outlines various types of instruction formats including one-byte instructions, register-to-register, and immediate operands, along with examples for each. Understanding these formats is essential for writing efficient code and executing operations effectively.

1. Instruction Format in 8086
Microprocessor
Unlocking the Core of Assembly
Language Programming

2. Introduction
• • The 8086 Microprocessor is widely
utilized in programming and
embedded systems.
• • To code efficiently, it’s essential to
understand instruction formats—how
they are structured and executed.

3. Basic Structure of an
Instruction Format
• • Opcode: Specifies the operation to be
performed.
• • Operands: Define the data to be
operated on.
• These fields determine how the CPU
interprets instructions.

4. Types of 8086 Instruction
Formats
• 1. One-byte Instruction
• 2. Register-to-Register
• 3. Register-to/from Memory without
Displacement
• 4. Register-to/from Memory with Displacement
• 5. Immediate Operand to Register
• 6. Immediate Operand to Memory with

5. Example: One-byte
Instruction
• • CLC: Clear Carry Flag
• • This instruction is compact, requiring
only one byte of space.
• • Efficiency: Ideal for small operations.
• Example Code:
• CLC ; Clears the carry flag.

6. Example: Register-to-Register
Format
• • Example: MOV CL, AL
• • Size: 2 bytes
• • Explanation: Moves the value from
register AL to register CL.
• Example Code:
• MOV CL, AL ; Move the value from AL
to CL register.

8. Example: Register-to/from
Memory with Displacement
• • Example: MOV AX, [BX+4]
• • Displacement: Specifies an offset for
memory addressing.
• • Usage: Vital for complex memory
operations.
• Example Code:
• MOV AX, [BX+4] ; Move the value from
memory at address [BX + 4] to AX.

9. Immediate Operand to
Register
• • Example: MOV AX, 1234H
• • Immediate Data: The instruction
directly includes the data value.
• • Practical Use: Useful for initializing
registers with fixed values.
• Example Code:
• MOV AX, 1234H ; Load the immediate
value 1234H into register AX.

10. Immediate Operand to
Memory with Displacement
• • Instruction includes immediate data
and references memory with an offset
(displacement).
• • Example: MOV [BX+4], 1234H
• ; Moves the immediate value 1234H
to the memory location computed by
BX + 4.
• Example Code:

11. Summary of Addressing
Modes
• • Immediate Addressing: Data is part
of the instruction.
• • Register Addressing: Operates
directly on registers.
• • Direct Addressing: Refers to a
memory location directly.
• • Register Indirect Addressing: Uses

12. Conclusion
• • Instruction formats in the 8086
microprocessor help define how
operations and operands are encoded.
• • Understanding these formats is
critical for writing efficient assembly
language code.