The 8086 microprocessor supports 8 types of instructions −

• Data Transfer Instructions
• Arithmetic Instructions
• Bit Manipulation Instructions
• String Instructions
• Program Execution Transfer Instructions (Branch & Loop Instructions)
• Processor Control Instructions
• Iteration Control Instructions
• Interrupt Instructions

1 Data Transfer Instructions These instructions are used to transfer the data from the source operand to the destination operand. Following are the list of instructions under this group −

Instruction to transfer a word

MOV − Used to copy the byte or word from the provided source to the provided destination.

PPUSH − Used to put a word at the top of the stack.

POP − Used to get a word from the top of the stack to the provided location.

PUSHA − Used to put all the registers into the stack.

POPA − Used to get words from the stack to all registers.

XCHG − Used to exchange the data from two locations.

XLAT − Used to translate a byte in AL using a table in the memory.

Instructions for input and output port transfer

IN − Used to read a byte or word from the provided port to the accumulator.

OUT − Used to send out a byte or word from the accumulator to the provided port.

Instructions to transfer the address

LEA − Used to load the address of operand into the provided register.

LDS − Used to load DS register and other provided register from the memory

LES − Used to load ES register and other provided register from the memory.

Instructions to transfer flag registers

LAHF − Used to load AH with the low byte of the flag register.

SAHF − Used to store AH register to low byte of the flag register.

PUSHF − Used to copy the flag register at the top of the stack.

POPF − Used to copy a word at the top of the stack to the flag register.

2 Arithmetic Instructions

These instructions are used to perform arithmetic operations like addition, subtraction, multiplication, division, etc.

Following is the list of instructions under this group −

Instructions to perform addition

ADD − Used to add the provided byte to byte/word to word.

ADC − Used to add with carry.

INC − Used to increment the provided byte/word by 1.

AAA − Used to adjust ASCII after addition.

DAA − Used to adjust the decimal after the addition/subtraction operation.

Instructions to perform subtraction

SUB − Used to subtract the byte from byte/word from word.

SBB − Used to perform subtraction with borrow.

DEC − Used to decrement the provided byte/word by 1.

NPG − Used to negate each bit of the provided byte/word and add 1/2’s complement.

CMP − Used to compare 2 provided byte/word.

AAS − Used to adjust ASCII codes after subtraction.

DAS − Used to adjust decimal after subtraction.

Instruction to perform multiplication

MUL − Used to multiply unsigned byte by byte/word by word.

IMUL − Used to multiply signed byte by byte/word by word.

AAM − Used to adjust ASCII codes after multiplication.

Instructions to perform division

DIV − Used to divide the unsigned word by byte or unsigned double word by word.

IDIV − Used to divide the signed word by byte or signed double word by word.

AAD − Used to adjust ASCII codes after division.

CBW − Used to fill the upper byte of the word with the copies of sign bit of the lower byte.

CWD − Used to fill the upper word of the double word with the sign bit of the lower word.

3 Bit Manipulation Instructions

These instructions are used to perform operations where data bits are involved, i.e. operations like logical, shift, etc.

Following is the list of instructions under this group −

Instructions to perform logical operation

NOT − Used to invert each bit of a byte or word.

AND − Used for adding each bit in a byte/word with the corresponding bit in another byte/word.

OR − Used to multiply each bit in a byte/word with the corresponding bit in another byte/word.

XOR − Used to perform Exclusive-OR operation over each bit in a byte/word with the corresponding bit in another byte/word.

TEST − Used to add operands to update flags, without affecting operands.

Instructions to perform shift operations

SHL/SAL − Used to shift bits of a byte/word towards left and put zero(S) in LSBs.

SHR − Used to shift bits of a byte/word towards the right and put zero(S) in MSBs.

SAR − Used to shift bits of a byte/word towards the right and copy the old MSB into the new MSB.

Instructions to perform rotate operations ROL − Used to rotate bits of byte/word towards the left, i.e. MSB to LSB and to Carry Flag [CF].

ROR − Used to rotate bits of byte/word towards the right, i.e. LSB to MSB and to Carry Flag [CF].

RCR − Used to rotate bits of byte/word towards the right, i.e. LSB to CF and CF to MSB.

RCL − Used to rotate bits of byte/word towards the left, i.e. MSB to CF and CF to LSB.

4 String Instructions String is a group of bytes/words and their memory is always allocated in a sequential order.

Following is the list of instructions under this group −

REP − Used to repeat the given instruction till CX ≠ 0.

REPE/REPZ − Used to repeat the given instruction until CX = 0 or zero flag ZF = 1.

REPNE/REPNZ − Used to repeat the given instruction until CX = 0 or zero flag ZF = 1.

MOVS/MOVSB/MOVSW − Used to move the byte/word from one string to another.

COMS/COMPSB/COMPSW − Used to compare two string bytes/words.

INS/INSB/INSW − Used as an input string/byte/word from the I/O port to the provided memory location.

OUTS/OUTSB/OUTSW − Used as an output string/byte/word from the provided memory location to the I/O port.

SCAS/SCASB/SCASW − Used to scan a string and compare its byte with a byte in AL or string word with a word in AX.

LODS/LODSB/LODSW − Used to store the string byte into AL or string word into AX.

5 Program Execution Transfer Instructions (Branch and Loop Instructions) These instructions are used to transfer/branch the instructions during an execution. It includes the following instructions −

Instructions to transfer the instruction during an execution without any condition −

CALL − Used to call a procedure and save their return address to the stack.

RET − Used to return from the procedure to the main program.

JMP − Used to jump to the provided address to proceed to the next instruction.

Instructions to transfer the instruction during an execution with some conditions −

JA/JNBE − Used to jump if above/not below/equal instruction satisfies.

JAE/JNB − Used to jump if above/not below instruction satisfies.

JBE/JNA − Used to jump if below/equal/ not above instruction satisfies.

JC − Used to jump if carry flag CF = 1

JE/JZ − Used to jump if equal/zero flag ZF = 1

JG/JNLE − Used to jump if greater/not less than/equal instruction satisfies.

JGE/JNL − Used to jump if greater than/equal/not less than instruction satisfies.

JL/JNGE − Used to jump if less than/not greater than/equal instruction satisfies.

JLE/JNG − Used to jump if less than/equal/if not greater than instruction satisfies.

JNC − Used to jump if no carry flag (CF = 0)

JNE/JNZ − Used to jump if not equal/zero flag ZF = 0

JNO − Used to jump if no overflow flag OF = 0

JNP/JPO − Used to jump if not parity/parity odd PF = 0

JNS − Used to jump if not sign SF = 0

JO − Used to jump if overflow flag OF = 1

JP/JPE − Used to jump if parity/parity even PF = 1

JS − Used to jump if sign flag SF = 1

6 Processor Control Instructions These instructions are used to control the processor action by setting/resetting the flag values.

Following are the instructions under this group −

STC − Used to set carry flag CF to 1

CLC − Used to clear/reset carry flag CF to 0

CMC − Used to put complement at the state of carry flag CF.

STD − Used to set the direction flag DF to 1

CLD − Used to clear/reset the direction flag DF to 0

STI − Used to set the interrupt enable flag to 1, i.e., enable INTR input.

CLI − Used to clear the interrupt enable flag to 0, i.e., disable INTR input.

7 Iteration Control Instructions These instructions are used to execute the given instructions for number of times. Following is the list of instructions under this group −

LOOP − Used to loop a group of instructions until the condition satisfies, i.e., CX = 0

LOOPE/LOOPZ − Used to loop a group of instructions till it satisfies ZF = 1 & CX = 0

LOOPNE/LOOPNZ − Used to loop a group of instructions till it satisfies ZF = 0 & CX = 0

JCXZ − Used to jump to the provided address if CX = 0

8 Interrupt Instructions These instructions are used to call the interrupt during program execution.

INT − Used to interrupt the program during execution and calling service specified.

INTO − Used to interrupt the program during execution if OF = 1

IRET − Used to return from interrupt service to the main program