A microprocessor is an electronic component that is used by a computer to do its work. It is a central processing unit on a single integrated circuit chip containing millions of very small components including transistors, resistors, and diodes that work together. Some microprocessors in the 20th century required several chips. Microprocessors help to do everything from controlling elevators to searching the Web. Everything a computer does is described by instructions of computer programs, and microprocessors carry out these instructions many millions of times a second. [1] Microprocessors were invented in the 1970s for use in embedded systems. The majority are still used that way, in such things as mobile phones, cars, military weapons, and home appliances. Some microprocessors are microcontrollers, so small and inexpensive that they are used to control very simple products like flashlights and greeting cards that play music when you open them. A few especially powerful microprocessors are used in personal computers.

1. Classificationof InstructionSet:
8086 instructions are classified as given below, based on its operation performed.
1. Data Transfer Instructions
2. Arithmetic Instructions
3. Bit Manipulation Instructions
4. Program Execution Transfer Instructions
5. String Instructions
6. Processor Control Instructions
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 Destination,Source:
• This instructionisusedtotransfercontentsof source tothe destination.
• The source operandcanbe a immediate,aregisterora memorylocationaddressedby
any of the 24 addressingmodes.
• The destinationcanbe a registerora memorylocation,butnotan immediate data.
• Both operandscannotbe immediate dataormemorylocation.
• To loadthe segmentregisterswithdata,anygeneral purpose registerisloadedwiththe
data firstand thenmovedtothat particularsegmentregister
E.g.:
MOV CX,037A H
MOV AL, BL
MOV BX,[0301 H]
MOV DS, AX
2. PUSH Source
 It pushesthe operandintotopof stack.
 The PUSH instructiondecrementsthe stackpointerby2 copiesaword fromsource to the
locationpointedbythe stackpointerwithinthe stacksegment.
 The source can be a general purpose register,memorylocationorasegmentregister.
E.g.: PUSH BX
PUSH DS
PUSH [2000h}
PUSH AL; not allowed
3. POP Destination
 It popsthe operandfromtop of stackto Destination.
 It copiesa wordfromthe locationpointedbythe stackpointerwithinthe stacksegmentto
the specifieddestinationand incrementsthe stackpointerby2.
 The source can be a general purpose register,memorylocationorasegmentregister.
E.g.: POPAX
POPDS
POP[3000h]
4. XCHG Destination,Source
 ThisinstructionexchangesSource withDestination.
 It cannot exchange twomemorylocationsdirectly.
 The source anddestinationcanbe anyof the general purpose registerormemorylocation,
but nottwo locationssimultaneously.
 No segmentregisterscanbe used.
E.g.: XCHG DX, AX
XCHG BL, CH
XCHG AL,[9800]
5. IN Accumulator, Port Address:
 It transfersthe operandfromspecifiedporttoaccumulator registerwhichcanbe AL or AX.
 The addressof the port isspecifiedinthe instruction eitherdirectly(fixedport) orindirectly
(variable portusingDXregister).
E.g.: IN AX, 80H
IN AL, DX ; DX may containthe addressof the portas 8000H

2. 6. OUT Port Address,Accumulator:
It transfersthe operandfromaccumulator AL or AX to specifiedport.
The addressof the port isspecifiedeitherdirectly(fixedport) orindirectly(variableportusingDX
register).
E.g.: OUT 80 H, AX
OUT DX,AL ; DX may containthe addressof the portas 8000H
7. LEA Register,Src:
It loadsa 16-bit registerwiththe offsetaddressof the dataspecifiedbythe Src.
E.g.: LEA BX,[DI]
Thisinstructionloadsthe contentsof DI(offset) intothe BXregister.
8. LDS Des,Src:
It loads32-bit pointerfrommemorysource todestination registerandDS.
The offsetisplacedinthe destinationregisterandthe segmentisplacedinDS.
To use thisinstructionthe wordat the lowermemoryaddressmustcontainthe offsetandthe word
at the higheraddressmustcontainthe segment.
E.g.: LDS BX, [0301 H]
9. LES Des,Src:
It loads32-bit pointerfrommemorysource todestinationregisterandES.
The offsetisplacedinthe destinationregisterandthe segmentisplacedinES.
ThisinstructionisverysimilartoLDS exceptthatitinitializesESinsteadof DS.
E.g.: LES BX, [0301 H]
10. LAHF:
It copiesthe lowerbyte of flagregistertoAH. Thisinstructionisusedtosimulate 8085 PUSH PSW
instruction.Thisaffectsnoflags.
E.g.: LAHF
11. SAHF:
It copiesthe contentsof AH to lowerbyte of flagregister. Thisinstructionisusedtosimulate 8085
POPPSW instruction.Thisaffectsthe lowerbyte of the flagregister.
E.g.: SAHF
12. PUSHF:
Pushesflagregistertotopof stack. Thisinstructiondecrementsthe stackpointerby2 and copies
the word inthe flagregistertothe memorylocationspointedbystackpointer.Noflagsare
changed.
E.g.: PUSHF
13. POPF:
Popsthe contentsof stack top to the flagregister. Thiscopiesawordfrom twomemorylocationsat
the top of the stack to the flagregisterandincrements the stackpointerbytwo.All flagsare
affected.
E.g.: POPF
14. XLAT
The XLAT (Translate) instructionreplacesabyte inALregisterwitha byte froma lookuptable in
memory.Before the execution,BXregistershouldbe loadedwiththe offsetof the lookup table.
XLAT instructionaddsthe ALbyte withthe offsetof the start of the table inBX andthencopiesthe
byte pointedbythismemorylocationbacktoAL. XLAT changesnoflags.
E.g: If AL ishavinga byte whose code isto be foundout,
MOV BX,2800H ; PointBX at the start of the table
XLAT ; replace the byte inAL withthe code in table.
Arithmetic Instructions
1. ADD Destination,Source
• Thisinstructionisusedto add the contentsof source to the destination.
• The resultisstoredin the destination.
• The source operandcanbe a immediate,aregisterora memorylocationaddressedby
any of the 24 addressingmodes.
• The destinationcanbe a registerora memorylocation,butnotan immediate data.
• Both operandscannotbe immediate dataormemorylocation.

3. • The source andthe destinationmustbe of the same data type i.e.,ADDinstruction
adds a byte to byte or a wordto word.
• It affectsAF,CF,OF, PF,SF,ZF flags.
E.g.:
ADD AL, 74H
ADD DX,AX
ADD AX,[BX]
2. ADC Destination,Source
• Thisinstructionisusedto add the contentsof source to the destinationandcarry flag.
• The resultisstoredin the destination.
• The source operandcanbe a immediate,aregisterora memorylocationaddressedby
any of the 24 addressingmodes.
• The destinationcanbe a registerora memorylocation,butnotan immediate data.
• Both operandscannotbe immediate dataormemorylocation.
• The source andthe destinationmustbe of the same data type i.e.,ADDinstruction
adds a byte to byte or a wordto word.
• It addsthe twooperandswithCF.
• It effectsAF,CF,OF,PF,SF, ZF flags.
E.g.:
ADC AL,74H
ADC DX,AX
ADC AX,[BX]
3. SUB Destination,Source
• Thisinstructionisusedto subtract the contentsof source from the destination.
• The resultisstoredin the destination.
• The source operandcanbe a immediate,aregisterora memorylocationaddressedby
any of the 24 addressingmodes.
• The destinationcanbe a registerora memorylocation,butnotan immediate data.
• Both operands cannotbe immediate dataormemorylocation.
• The source andthe destinationmustbe of the same data type i.e.,SUBinstruction
subtractsa byte frombyte or a word fromword.
• It affectsAF,CF,OF, PF,SF,ZF flags.
• For subtraction,CFacts as borrow flag.
E.g.:
SUB AL, 74H
SUB DX, AX
SUB AX, [BX]
4. SBB Destination,Source
• Thisinstructionisusedto subtract the contentsof source withborrow from the
destination.
• The resultisstoredin the destination.
• The source operandcanbe a immediate,aregisteror a memorylocationaddressedby
any of the 24 addressingmodes.
• The destinationcanbe a registerora memorylocation,butnotan immediate data.
• Both operandscannotbe immediate dataormemorylocation.
• The source andthe destinationmustbe of the same data type i.e.,SUBinstruction
subtractsa byte frombyte or a word fromword.
• It affectsAF,CF,OF, PF,SF,ZF flags.
• For subtraction,CFacts as borrow flag.
E.g.:
SBB AL, 74H
SBB DX, AX
SBB AX,[BX]
5. INC Destination
• It incrementsthe byte orword in destination byone.
• The destinationoperandcanbe a registerora memorylocationaddressedbyanyof the
24 addressingmodes.
• It affectsAF,OF,PF,SF, ZF flags.

4. • CF isnot affected.
E.g.:
INC AX
INCBL
6. DEC Destination
• It decrementsthe byte orword indestination byone.
• The destinationoperandcanbe a registerora memorylocationaddressedbyanyof the
24 addressingmodes.
• It affectsAF,OF,PF,SF, ZF flags.
• CF isnot affected.
E.g.:
DEC AX
DEC CL
7. DAA (Decimal Adjust Accumulator)
Syntax :-- DAA
• This instructionisusedtoconvertthe resultof the additionof twopackedBCD
numberstoa validBCDnumber.
• The resulthasto be onlyin AL.
• Afteradditionif the lowernibble isgreaterthan9 or AF =1, it will add06H to the lower
nibble inAL.
• Afterthisaddition,if the uppernibbleisgreaterthan9 or if CF = 1, DAA instruction
adds 60H to AL.
• DAA instructionaffectsAF,CF,PFandZF. OFisundefined.
OperationPerformed:--
– If lowernibble of AL> 9 or AF =1 thenAL = AL +06
– If highernibble of AL> 9 or CF =1 thenAL = AL +60
NumericExamples
AL = 53H, CL = 29H
ADD AL,CL ; AL  AL + CL
;AL  53 + 29
;AL  7CH
DAA ; AL 7C +06 (asC>9)
;AL 82
8. DAS (Decimal Adjust AfterSubtraction)
Syntax :-- DAS
• This instructionisusedtoconvertthe resultof the subtractionof twopackedBCD
numberstoa validBCDnumber.
• The subtractionhasto be onlyin AL.
• Aftersubtractionif the lowernibble isgreaterthan9or AF=1, it will subtract06H from
the lowernibble inAL.
• If the resultof the subtractionsetsthe carry flag or if the uppernibble isgreaterthan9,
DAS instructionsubtracts60H fromAL.
• DAS instructionaffectsAF,CF,PFandZF.OFis undefined.
OperationPerformed:--
– If lowernibble of AL> 9 or AF =1 thenAL = AL -06
– If highernibble of AL> 9 or CF =1 thenAL = AL -60
NumericExamples
AL = 75, BH = 46
SUB AL,BH ; AL  (AL) - (BH)
;AL  75 - 46
;AL  2FH
; AF = 1
DAS ; AL 2F - 06 (as F>9)
;AL 29
9. MUL (Unsignedmultiplication)
Syntax :-- MUL source

5. • This instructionmultipliesan unsignedbyte fromsource withan unsignedbyte in AL
register
or
Unsignedword fromsource withanunsignedwordin AX register.
• The source can be a registerormemorylocationbutcannotbe an immediatedata.
• Whena byte is multipliedwithabyte inAL, the resultisstoredinAX.
• Whena wordis multipliedwithawordinAX,the MSW (Most SignificantWord) of the
resultisstoredinDX and the LSW (LeastSignificantWord) of the resultisstoredinAX.
• If MS Byte or Word of the resultiszero,CF and OF bothwill be set.
• All otherflagsare modifieddependinguponthe result
OperationPerformed:--
– If source isbyte thenAX  AL * unsigned8bitsource
– If source iswordthenDX, AX  AX * unsigned16 bitsource
Examples:--
1. MUL BL ; MultiplyALby BL & the resultinAX
2. MUL CX ; MultiplyAXbyCX & the resultinDX,AX
3. MUL Byte PTR [SI] ; AX  AL * [SI]
10. IMUL (Signedmultiplication)
Syntax :-- IMUL source
• This instructionmultipliesa signedbyte fromsource witha signedbyte in ALregister
or
signedword fromsource withan signedwordin AX register.
• The source can be a register,general purpose,base orindex,ormemorylocation,but
cannot be an immediate data.
• Whena byte is multipliedwithabyte inAL, the resultisstoredinAX.
• Whena wordis multipliedwithawordinAX,the MSW (Most SignificantWord) of the
resultisstoredinDX and the LSW (LeastSignificantWord) of the resultisstoredinAX.
• If the magnitude of the productdoesnotrequire all the bitsof the destination,the
unusedbitsare filledwithcopiesof the signbit.
• If AH and DX containparts of the 16 & 32 bit results,CFandOF are set,If the unused
bitsare filledbythe signbit,OFandCF are cleared.
OperationPerformed:--
• If source isbyte thenAX  AL * signed8bit source
• If source iswordthenDX, AX  AX * signed16 bit source
Examples:--
1. IMUL BL ; MultiplyALby BL & the resultinAX
2. IMUL CX ; MultiplyAXbyCX & the resultinDX,AX
3. IMUL Byte PTR [SI] ; AX  AL * [SI]
•
11. DIV (UnsignedDivision)
Syntax :-- DIV source
• This instructiondividesanunsigned word(16Bits) in AX registerbyan unsigned byte
(8Bits) fromsource
or
an unsigned double word(32 bits) in DX & AX registerbyan unsigned word(16bits)
fromsource
• The source can be a registerormemorylocationbutcannotbe an immediatedata.
• Whena word inAX isdividedbyabyte,AL will containthe 8 bitquotientandAHwill
containan 8 bitremainder.
• Whena double wordinDX(MSW) & AX (LSW) isdividedbya word,AX will containthe
16 bit quotientandDXwill containan16 bitremainder.
• If a byte isto be dividedbya byte,ALis loadedwithdividendandAHisfilledwithall 0’s.
• If a wordis to be dividedbyaword,Ax is loadedwithdividendandDXis filledwithall
0’s.

6. • If an attemptismade to divide by0,or the quotientistoolarge (FFor FFFF),type 0
interruptisgenerated.
• No flagsare affected.
OperationPerformed:--
• If source isbyte then
• AL  AX/ unsigned8bit source ; (quotient)
• AH  AXMOD unsigned8bitsource ; (remainder)
• If source iswordthen
• AX  DX:AX/ unsigned16 bitsource ; (quotient)
• DX  DX:AXMOD unsigned16 bitsource ; (remainder)
Examples:--
1. DIV BL ; Divide wordinAXby byte in BL, Quotientisstoredin AL,
remainderinAH.
2. DIV CX ; Divide double wordinDX:AX bywordinCX,QuotientinAX,
RemainderinDX.
3. DIV [BX] ; Divide wordinAXby byte in memorylocationpointerby BX.
12. CBW (ConvertSignedByte to Word)
Syntax :-- CBW
• This instructionconvertsasignedbyte toa signedword.
• Thisinstructioncopiesthe signof a byte inAL to all the bitsin AH.
• AH is thensaidto be the signextensionof AL.
• CBW operationisdone before performingdivisionof asignedbyte inthe ALby another
signedbyte withIDIV instruction.
Operation :--
• AH  filledwith8th
bitof AL i.e.,D7
Thisdoesnot affectanyflags.
Example :--
If AX = 009BH, (00000000 10011011
AfterCBW Instruction,
AX=FF9B (11111111 10011011)
13. CWD (ConvertSignedWordto Double Word)
Syntax :-- CWD
• This instructioncopiesthe signbitof aword inAXto all the bitsinDX.
• Thus the signof AXis saidto be extendedtoDX.
• CWD operationisdone before performingdivisionof asignedwordinthe AXby
anothersignedwordwithIDIV instruction.
Operation :--
• DX filledwith16th
bitof AXi.e.,D15
Thisdoesnot affectanyflags.
Example :--
If DX = 0000H (00000000 00000000)
If AX = F0C7H, (11110000 11000111)
AfterCWD Instruction,
DX = FFFFH (11111111 11111111)
AX=F0C7 (11110000 11000111)
14. CMP (Compare)
Syntax :-- CMP destination,source
• Thisinstructioncomparesthe source operand,whichmaybe a register,immediate
data or memorylocationwithadestinationoperandwhichmaybe a registeror
memorylocation.
• It subtractsthe source operandfromthe destinationbutdoesnotstore the result
anywhere.
• The flags(OF,CF, PF,AF,SF, ZF)are affecteddependingonthe resultof subtraction.
• Source and destinationbothcannotbe memorylocations.

7. OperationPerformed:--
• If destination>source thenCF = 0, ZF = 0, SF = 0
• If destination<source thenCF = 1, ZF = 0, SF = 1
• If destination=source thenCF = 0, ZF = 1, SF = 0
Examples:--
1. CMP AL,0FFH; ComparesAL withFFH
2. CMP AX,BX ; ComparesAX withBX
3. CMP CX,COUNT ; ComparesCXwithmemory variable COUNT
15. NEG ( Negate )
Syntax :-- NEG destination
• This instructionreplacesthe numberinthe destinationwiththe 2’scomplementof that
number.
• For obtainingthe 2’scomplement,itsubtractsthe contentsof destinationfromzero.
• The resultisstoredback in the destinationwhichmaybe a registerora memory
location
• If OF =1, it indicatesthatthe operationcouldnotbe completedsuccessfully.
• NEG instructionaffectsall conditionalflags.
• Examples:--
1. NEG AL ; 2’s complementof ALbyte.
2. NEG BX ; 2’s complementof BXword.
• Logical Instructions
– These are the instructions used for basic logic operations such as AND, OR, NOT
and XOR.
– These are also used for carrying out bit by bit operations such as shift (SHR,SHL)
or rotate (ROL,ROR,RCR,RCL).
– One more Instruction under this category is TEST instruction.
AND (Logical AND)
Syntax :-- AND destination, source
• This instruction is used to bit by bit AND the contents of source to the destination.
• The result is stored in the destination.
• The source operand can be a immediate, a register or a memory location.
• The destination can be a register or a memory location, but not an immediate data.
• Both operands cannot be immediate data or memory location.
• Flags affected : OF = 0 ,CF = 0 , AF is undefined.
• And other flags (SF, ZF, PF) are affected based on the AND operation.
• Operation Performed :--
• Destination  Destination AND source
• Examples :--
1. AND BH,CL ;AND byte in CL with Byte in BH, result in BH.
2. AND BX,00FFH ;AND word in BX with immediate data 00ffH
3. AND [5000H], DX ;AND word in DX with a word in memory with offset
5000 in DS.
• Numeric Example
If AX = 3F0F,
After Instruction,
AND AX,9078H ; AX  AX AND 0008H
;AX  3F0F AND 0008
3F0F  0011 1111 0000 1111
AND
9078  1001 0000 0111 1000
-------------------------------------
= 0001 0000 0000 1000
1008H in AX register
OR (Logical OR)

8. Syntax :-- OR destination, source
• This instruction is used to bit by bit OR the contents of source to the destination.
• The result is stored in the destination.
• The source operand can be a immediate, a register or a memory location.
• The destination can be a register or a memory location, but not an immediate data.
• Both operands cannot be immediate data or memory location.
• Flags affected : OF = 0 ,CF = 0 , AF is undefined.
• And other flags (SF, ZF, PF) are affected based on the OR operation.
Operation Performed :--
Destination  Destination OR source
• Examples :--
1. OR BH,CL ;OR byte in CL with Byte in BH, result in BH.
2. OR BX,00FFH ;OR word in BX with immediate data 00ffH
3. OR [5000H], DX ; OR word in DX with a word in memory with offset 5000
in DS.
Numeric Example
If AX = 3F0F,
After Instruction,
OR AX,9078H ; AX  AX OR 9078H
;AX  3F0F OR 9078
3F0F  0011 1111 0000 1111
OR
9078  1001 0000 0111 1000
-------------------------------------
= 1011 1111 0111 1111
BF7FH in AX register
XOR (Logical XOR)
Syntax :-- XOR destination, source
• This instruction is used to bit by bit XOR the contents of source to the destination.
• The result is stored in the destination.
• The source operand can be a immediate, a register or a memory location.
• The destination can be a register or a memory location, but not an immediate data.
• Both operands cannot be immediate data or memory location.
• Flags affected : OF = 0 ,CF = 0 , AF is undefined.
• And other flags (SF, ZF, PF) are affected based on the XOR operation.
Operation Performed :--
Destination  Destination XOR source
• Examples :--
1. XOR BH,CL ;XOR byte in CL with Byte in BH, result in BH.
2. XOR BX,00FFH ;XOR word in BX with immediate data 00ffH
3. XOR [5000H], DX ; XOR word in DX with a word in memory with offset 5000 in
DS.
Numeric Example
If AX = 3F0F,
After Instruction,
XOR AX,9078H ; AX  AX XOR 0008H
;AX  3F0F XOR 0008
3F0F  0011 1111 0000 1111
XOR
9078  1001 0000 0111 1000
-------------------------------------
= 1010 1111 0111 0111
AF77H in AX register
NOT (Logical Invert )

9. Syntax :-- NOT destination
• This instruction complements (inverts) each bit of the byte or word stored in the
destination.
• The result is stored in the destination.
• The destination can be a register or a memory location.
• No Flags affected
Operation Performed :--
• Destination  NOT Destination
• Examples :--
1. NOT BH ;Complement byte in BH, result in BH.
2. NOT BX ; Complement word in BX, result in BX.
3. NOT BYTE PTR [5000H] ; Complement byte in memory with offset 5000 in DS.
Numeric Example
If AX = 3F0F,
After Instruction,
NOT AX ; AX  NOT AX
;AX  NOT 3F0F
3F0F  0011 1111 0000 1111
Complement
-------------------------------------
= 1100 0000 1111 0000
C0F0H in AX register
TEST (Logical compare )
Syntax :-- TEST destination, source
• This instruction is used to bit by bit AND the contents of source to the destination.
• The result is not stored in the destination.
• The source operand can be a immediate, a register or a memory location.
• The destination can be a register or a memory location, but not an immediate data.
• Both operands cannot be immediate data or memory location.
• Flags affected : OF = 0 ,CF = 0 , SF, ZF, PF.
• TEST instruction is used to set flags before a conditional jump instruction
Operation Performed :--
• Flags  set result of Destination AND source
• Examples :--
1. TEST BH,CL ;AND byte in CL with Byte in BH, no result but flags are affected.
2. TEST BX,00FFH ;AND word in BX with immediate data 00ffH, no result
but flags are affected.
3. TEST DX, [5000H] ;AND word in DX with a word in memory with offset
5000 in DS, no result but flags are affected.
SHL / SAL (Shift Logical/Arithmetic Left)
Syntax :-- SHL/SAL destination, count
• SHL & SAL are the opcodes for the same operation
• This instruction shifts the destination bit by bit to the left and insert zeroes in the newly
introduced least significant bits.
• The shift operation is through carry.
• The count can be either 1 or specified by CL register.
• The destination can be a byte or a word in register or a memory location, but not an
immediate data.

10. • Flags affected : OF ,CF, SF, ZF, PF.
• These instructions can be used to multiply an unsigned number by power of 2.
Operation Performed :--
CF  MSB LSB  0
Example :--
If CF = 0, BX = E6D3H
After SAL BX, 1 ; Shift the contents of BX register by one towards left
BX = CDA6
Example :--
Use of SHL instruction for Multiplication:-
If CF = 0, BH = 04H
MOV CL, 03 ; Load CL register for the count
SHL BH, CL ; Shift the contents of BX register by one towards left
BH = 20H (32D) [ 04 * 23 = 32 D]
Note :-- SHL can be used to multiply a number with powers of 2.
BH = 20H with CF = 0
SAR (Shift Arithmetic Right )
Syntax :-- SAR destination, count

11. • This instruction shifts the destination bit by bit to the right and MSB position is kept in
the old MSB position
• The shift operation is through carry, LSB is shifted to CF.
• The count can be either 1 or specified by CL register.
• The destination can be a byte or a word in register or a memory location, but not an
immediate data.
• Flags affected : OF ,CF, SF, ZF, PF.
• This instruction can be used to divide an unsigned number by power of 2.
Operation Performed :--
MSB LSB  CF
Example1 :--
If CF = 0, BX = E6D3H
After SAR BX, 1 ; Shift the contents of BX register by one towards right
BX = F369H with CF =1
Example2 :--
• Use of SAR instruction for Division:-
If CF = 0, BH = 14H
MOV CL, 02 ; Load CL register for the count
SAR BH, CL ; Shift the contents of BX register by one towards right
BH = 05H (20D) [ 20 / 22 = 05D]
BH = 05H with CF = 0

12. Note :-- SAR can be used to divide a number with powers of 2 and get the quotient.
SHR (Shift Logical Right)
Syntax :-- SHR destination, count
• This instruction shifts the destination bit by bit to the right and insert zeroes in the
newly introduced most significant bits.
• The shift operation is through carry.
• The count can be either 1 or specified by CL register.
• The destination can be a byte or a word in register or a memory location, but not an
immediate data.
• Flags affected : OF ,CF, SF, ZF, PF.
Operation Performed :--
0  MSB LSB  CF
Example :--
If CF = 0, BX = E6D3H
After SHR BX, 1 ; Shift the contents of BX register by one towards right
BX = 7369H
ROR (Rotate Right without Carry)
Syntax :-- ROR destination, count
• This instruction rotates the destination bit by bit to the right excluding the carry
• The bit moved out of LSB is rotated around into the MSB and also copied to CF.
• The count can be either 1 or specified by CL register.
• The destination can be a byte or a word in register or a memory location, but not an
immediate data.
• Flags affected : OF ,CF
Operation Performed :--
MSB LSB  CF

13. Example 1:--
If CF = 0, BX = E6D3H
After ROR BX, 1 ; Rotate the contents of BX register by one towards right
BX = F369H
Example2 :--
If CF = 0, BH = 54H
MOV CL, 02 ; Load CL register for the count
ROR BH, CL ; Rotate the contents of BH register by twice towards right
BH = 15H with CF = 0
Uses of ROR instruction:--
• This instruction can be used to swap the nibbles in a byte or to swap the bytes in a
word.
MOV CL,04H
ROR AL, CL
• It can also be used to rotate the bit into CF which can be checked later for a conditional
jump. (JC or JNC)
ROL (Rotate Left without Carry)
Syntax :-- ROL destination, count
• This instruction rotates the destination bit by bit to the left excluding the carry
• The bit moved out of MSB is rotated around into the LSB and also copied to CF.
• The count can be either 1 or specified by CL register.

14. • The destination can be a byte or a word in register or a memory location, but not an
immediate data.
• Flags affected : OF ,CF
Operation Performed :--
CF MSB LSB
Example1 :--
If CF = 0, BX = E6D3H
After ROL BX, 1 ; Rotate the contents of BX register by one towards left
BX = CDA7H
Example2 :--
If CF = 0, BH = 54H
MOV CL, 02 ; Load CL register for the count
ROL BH, CL ; Rotate the contents of BH register by twice towards Left
BH = 51H with CF = 1
Uses of ROL instruction:--
• This instruction can be used to swap the nibbles in a byte or to swap the bytes in a
word.
MOV CL,04H
ROL AL, CL
• It can also be used to rotate the bit into CF which can be checked later for a conditional
jump. (JC or JNC)

15. RCR (Rotate Right withCarry)
Syntax :-- RCR destination, count
• This instruction rotates the destination bit by bit to the right including the carry
• The bit moved out of LSB is rotated into CF and the bit in CF is rotated into the MSB.
• The count can be either 1 or specified by CL register.
• The destination can be a byte or a word in register or a memory location, but not an
immediate data.
• Flags affected : OF ,CF
Operation Performed :--
MSB LSB  CF
Example1 :--
If CF = 0, BX = E6D3H
After RCR BX, 1 ; Rotate the contents of BX register by one towards right through carry
Example2 :--
If CF = 0, BH = 54H
MOV CL, 02 ; Load CL register for the count
RCR BH, CL ; Rotate the contents of BH register by twice towards right through
carry
BH = 15H with CF = 0

16. RCL (Rotate Left withCarry)
Syntax :-- RCL destination, count
• This instruction rotates the destination bit by bit to the left including the carry
• The bit moved out of MSB is rotated into CF and the bit in CF is rotated into the
LSB.
• The count can be either 1 or specified by CL register.
• The destination can be a byte or a word in register or a memory location, but not
an immediate data.
• Flags affected : OF ,CF
Operation Performed :--
– CF MSB LSB
Example :--
If CF = 0, BX = E6D3H
After RCL BX, 1 ; Rotate the contents of BX register by one towards left through carry
BX = CDA6H
Example :--
If CF = 0, BH = 54H
MOV CL, 02 ; Load CL register for the count
RCL BH, CL ; Rotate the contents of BH register by twice towards Left through carry