The document categorizes and describes the different types of instructions in the 8086 instruction set. It discusses data transfer instructions, logical instructions, shift and rotate instructions, arithmetic instructions, string instructions, branch and loop instructions, and miscellaneous instructions. For each category, it lists the specific instruction names and provides a brief description of what each instruction does.
2. Classification of Instruction Set
Data Transfer Instructions
Logical & Shift & Rotate Instructions
Arithmetic Instructions
String Instructions
Branch & Loop Instructions
Miscellaneous Instructions
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3. Data Transfer Instructions
These instructions are used to transfer data
from source to destination.
The operand can be a constant, memory
location, register or I/O port address.
1. MOV-Copy byte or word from source to
destination
2. PUSH-Copy specified word to top of stack
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4. Data Transfer Inst.(continue)
3. POP-Copy word from top of stack to specified
location
4. XCHG-Exchange bytes or exchange words
5. IN-Copy a byte or word from specified port to acc.
6. OUT-Copy a byte or word from acc.to specified port
7. XLAT-Translate a byte in AL using table in memory
8. LEA-Load Effective address of operand into specified
register
9. LAHF-Load AH with the lower byte of the flag
register
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5. Data Transfer Inst.(continue)
10. LDS/LES-Load pointer to DS/ES.i.e.loads DS/ES
register and other specified register from memory
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6. Logical Instructions
1. AND-AND each bit in a byte or word with the
corresponding bit in another byte or a word
2. OR-OR each bit in a byte or word with the
corresponding bit in another byte or a word
3. NOT-Invert each bit of a byte or word
4. XOR-Exclusive-OR each bit in a byte or word with
the corresponding bit in another byte or a word
5. TEST-AND operands to update flags,but don’t
change operands
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7. Shift & Rotate Instructions
1. SHL/SAL-Shifts bits or byte or word left, put zero(‘s)
in LSB(‘s)
2. SHR-Shifts bits or byte or word right, put zero(‘s) in
MSB(‘s)
3. SAR-Shifts bits or byte or word right, copy old MSB
into new MSB
4. ROR-Rotate bits of byte or word right, LSB to MSB
and to CF
5. ROL-Rotate bits of byte or word left, MSB to MSB
and to CF
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8. Shift & Rotate Instructions
6. RCR-Rotate bits of byte or word right, LSB to CF and
CF to MSB.
7. RCL-Rotate bits of byte or word left, MSB to CF and
CF to LSB
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9. Arithmetic Instructions
1. ADD-Add specified byte to byte or specified word to
word
2. ADC-Add byte + byte +CF or word+word+CF
3. INC- Increment specified byte or specified word by 1
4. DEC- Decrement specified byte or specified word by1
5. SUB-Subtract byte from byte or word from word
6. SBB- Subtract byte from byte with borrow(CF)
7. CMP-Compare to specified byte or specified word
8. NEG-Forms 2’s compliment
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10. Arithmetic Instructions
9. MUL- Multiply unsigned byte by byte or unsigned
word by word
10. IMUL- Multiply signed byte by byte or unsigned
word by word
11. DIV- Divide unsigned word by byte or unsigned
double word by word
12. IDIV- Divide signed word by byte or signed double
word by word
13. AAA-ASCII adjust after addition
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11. Arithmetic & ASCII Inst.
14. AAS- ASCII adjust after subtraction
15. AAM-ASCII adjust after multiplication
16. AAD-ASCII adjust before division
17. DAA-Decimal(BCD) adjust after addition
18. DAS-Decimal(BCD) adjust after subtraction
19. CBW-Fill upper byte or word with copies of sign bit
of lower byte
20. CWD-Fill upper word of double word with sign bit of
lower word
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12. String Instructions
There are very strong set of string instructions in 8086.
By using these string instructions, the size of the
program is considerably reduced.
1. REPE/REPZ-Repeat instruction on until CX=O or ZF
not equals to 1
2. REP-Repeat instruction on until CX=O
3. MOVS/MOVSB/MOVSW-Move byte or word from
one string to another
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13. String Instructions
4. REPNE/REPNZ-Repeat until CX=O or ZF=1
5. CMPS/CMPSB/CMPSW-Compare two string bytes
or two string words
6. SCAS/SCASB/SCASW-Scan a string. Compare a
string byte with a byte in AL or a string word with a
word in AX
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14. Conditional Jump Table
Mnemonic Meaning Jump Condition
JA Jump if Above CF = 0 and ZF = 0
JAE Jump if Above or Equal CF = 0
JB Jump if Below CF = 1
JBE Jump if Below or Equal CF = 1 or ZF = 1
JC Jump if Carry CF = 1
JE/JZ Jump if Equal ZF = 1
JNC Jump if Not Carry CF = 0
JNE Jump if Not Equal ZF = 0
JNZ Jump if Not Zero ZF = 0
JPE Jump if Parity Even PF = 1
JPO Jump if Parity Odd PF = 0
JMP Unconditional Jump -
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15. Branch & Loop Inst.
1. CALL-Call a procedure(sub-program),save return
address on stack
2. RET- Return from procedure to calling program
3. JNO-Jump if not overflow(OF=0)
4. JO-Jump if OF=1
5. JS-Jump if SF=1
6. INTO-Interrupt program execution if OF=1
7. LOOP-Loop through a sequence of instructions
until CX=O
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16. Branch & Loop Inst.
8. JCXZ-Jump to specified address if CX=O.
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17. Miscellaneous Instructions
1. CLC-Clear carry flag to zero
2. STC-Set the carry flag to ONE
3. STD-Set DF=1 and decrement SP
4. CMP-Compliment the state of carry flag(CF)
5. STI-Set IE=1(Enable INTR input)
6. CLD-Clear DF=O
7. HLT-Halt the programs
8. CLI-IE=O.(Disable INTR input)
9. WAIT-wait until signal on the TEST pin is low
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18. Miscellaneous Instructions
10. NOP-No action except fetch and decode
11. LOCK-Prevents another processor from taking the
bus while the adjacent instruction executes.
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