Instruction Set of the 8086 Microprocessor

Instruction Set of the 8086 Microprocessor The Intel 8086 microprocessor, unveiled in 1978, is a 16-bit processor renowned for its extensive and adaptable instruction set, which facilitates a broad spectrum of programming tasks. This encompassing set comprises instructions for data transfer, arithmetic operations, logical operations, control flow, and string manipulation. Data Transfer Instructions The following instructions are utilized for transferring data among registers, memory locations, and input/output devices.  MOV: Moves data from one location to another.  MOV AX, BX: Moves the contents of the BX register to the AX register.  MOV [1000H], AX: Moves the contents of the AX register to memory location 1000H.  PUSH: Pushes a word onto the stack.  PUSH AX: Pushes the contents of the AX register onto the stack.  POP: Pops a word off the stack and stores it in a register or memory location.  POP BX: Pops the top word off the stack and stores it in the BX register.  XCHG: Exchanges the contents of two registers or a register and a memory location.  XCHG AX, BX: Exchanges the contents of the AX and BX registers.  IN: Reads a byte or word from an input port.  IN AL, 80H: Reads a byte from input port 80H and stores it in the AL register.  OUT: Writes a byte or word to an output port.  OUT 80H, AL: Writes the contents of the AL register to output port 80H. Arithmetic Instructions The following instructions are designed to execute arithmetic operations on data.  ADD: Adds two operands.  ADD AX, BX: Adds the contents of the BX register to the contents of the AX register.  SUB: Subtracts one operand from another.  SUB AX, BX: Subtracts the contents of the BX register from the contents of the AX register.     MUL: Multiplies two operands.  MUL BX: Multiplies the contents of the AX register by the contents of the BX register. DIV: Divides one operand by another.  DIV BX: Divides the contents of the DX:AX register pair by the contents of the BX register. INC: Increments an operand by 1.  INC AX: Increments the contents of the AX register by 1. DEC: Decrements an operand by 1.  DEC AX: Decrements the contents of the AX register by 1. Logical Instructions The following instructions are designed to execute logical operations on data.  AND: Performs a bitwise AND operation on two operands.  AND AX, 0FH: Performs a bitwise AND operation between the contents of the AX register and the immediate value 0FH.  OR: Performs a bitwise OR operation on two operands.  OR AX, 0FH: Performs a bitwise OR operation between the contents of the AX register and the immediate value 0FH.  XOR: Performs a bitwise XOR operation on two operands.  XOR AX, 0FH: Performs a bitwise XOR operation between the contents of the AX register and the immediate value 0FH.  NOT: Performs a bitwise NOT operation on an operand.  NOT AX: Inverts all bits of the AX register. Control Flow Instructions The following instructions dictate the sequence of operations within a program.  JMP: Unconditionally jumps to a specified address.  JMP 1000H: Jumps to memory location 1000H.  JCC: Jumps to a specified address if a condition is met.  JZ 1000H: Jumps to memory location 1000H if the zero flag is set.  CALL: Calls a subroutine.  CALL SUBROUTINE: Calls the subroutine labeled "SUBROUTINE".  RET: Returns from a subroutine.  RET: Returns from the current subroutine.  LOOP: Repeats a block of code a specified number of times.  LOOP LABEL: Repeats the code between the current instruction and the label "LABEL" until the CX register becomes zero. String Manipulation Instructions The following instructions are utilized for the manipulation of character strings.  MOVS: Moves a string from one location to another.  MOVS [DI], [SI]: Moves a byte from the memory location pointed to by SI to the memory location pointed to by DI.  CMPS: Compares two strings.  CMPS [DI], [SI]: Compares the byte at the memory location pointed to by DI with the byte at the memory location pointed to by SI.  SCAS: Scans a string for a specific character.  SCASB: Scans a string for the character in the AL register.  Additional Instructions  LEA: Loads the effective address of an operand into a register.  LES: Loads the effective address of an operand into a segment register and a general-purpose register.  LDS: Loads the effective address of an operand into a segment register and a general-purpose register.  CLD: Clears the direction flag.  STD: Sets the direction flag.  CLI: Clears the interrupt flag.  STI: Sets the interrupt flag.  HLT: Halts the processor.  The 8086 instruction set is outlined briefly in this document. When creating assembly language programs, it is crucial to take into account the distinct variations and usage guidelines for each instruction. Programmers who comprehend and employ these instructions effectively can develop efficient and robust applications for the 8086 microprocessor.