COMPLETE 8086 INSTRUCTION SET

Quick Reference:

AAA
AAD
AAM
AAS
ADC
ADD
AND
CALL
CBW
CLC
CLD
CLI
CMC
CMP
CMPSB
CMPSW
CWD
DAA
DAS
DEC
DIV
HLT
IDIV
IMUL
IN
INC
INT
INTO
IRET
JA
JAE
JB
JBE
JC
JCXZ
JE
JG
JGE
JL
JLE
JMP
JNA
JNAE
JNB
JNBE
JNC
JNE
JNG
JNGE
JNL
JNLE
JNO
JNP
JNS
JNZ
JO
JP
JPE
JPO
JS
JZ
LAHF
LDS
LEA
LES
LODSB
LODSW
LOOP
LOOPE
LOOPNE
LOOPNZ
LOOPZ
MOV
MOVSB
MOVSW
MUL
NEG
NOP
NOT
OR
OUT
POP
POPA
POPF
PUSH
PUSHA
PUSHF
RCL
RCR
REP
REPE
REPNE
REPNZ
REPZ
RET
RETF
ROL
ROR
SAHF
SAL
SAR
SBB
SCASB
SCASW
SHL
SHR
STC
STD
STI
STOSB
STOSW
SUB
TEST
XCHG
XLATB
XOR

Operand Types:

REG: AX, BX, CX, DX, AH, AL, BL, BH, CH, CL, DH, DL, DI, SI, BP, SP.
SREG: DS, ES, SS, and only as second operand: CS.
Memory: [BX], [BX+SI+7], variable, etc…
Immediate: 5, -24, 3Fh, 10001101b, etc...

Notes:

• When two operands are required for an instruction they are separated by comma. For example:

REG, memory

• When there are two operands, both operands must have the same size (except shift and rotate instructions). For example:

AL, DL DX, AX m1 DB ? AL, m1 m2 DW ? AX, m2

• Some instructions allow several operand combinations. For example:

memory, immediate REG, immediate memory, REG REG, SREG

• Some examples contain macros, so it is advisable to use Shift + F8 hot key to Step Over (to make macro code execute at maximum speed set step delay to zero), otherwise emulator will step through each instruction of a macro. Here is an example that uses PRINTN macro:

include 'emu8086.inc' ORG 100h MOV AL, 1 MOV BL, 2 PRINTN 'Hello World!' ; macro. MOV CL, 3 PRINTN 'Welcome!' ; macro. RET
These marks are used to show the state of the flags:

1 - instruction sets this flag to 1.
0 - instruction sets this flag to 0. r - flag value depends on result of the instruction.
? - flag value is undefined (maybe 1 or 0).

Some instructions generate exactly the same machine code, so disassemble may have a problem decoding to your original code. This is especially important for Conditional Jump instructions (see "Program Flow Control" in Tutorials for more information).

Instructions in alphabetical order:

|INSTRUCTION |OPERANDS |DESCRIPTION |
|AAA |No operands |ASCII Adjust after Addition. |
| | |Corrects result in AH and AL after addition when |
| | |working with BCD values. |
| | |It works according to the following Algorithm: |
| | |if low nibble of AL > 9 or AF = 1 then: |
| | |������ AL = AL + 6 |
| | |������ AH = AH + 1 |
| | |������ AF = 1 |
| | |������ CF = 1 |
| | |else |
| | |������ AF = 0 |
| | |������ CF = 0 |
| | |in both cases: |
| | |clear the high nibble of AL. |
| | |Example: |
| | |MOV AX, 15 ; AH = 00, AL = 0Fh |
| | |AAA ; AH = 01, AL = 05 |
| | |RET |
|AAD |No operands |ASCII Adjust before Division. |
| | |Prepares two BCD values for division. |
| | |Algorithm: |
| | |������ AL = (AH * 10) + AL |
| | |������ AH = 0 |
| | |Example: |
| | |MOV AX, 0105h ; AH = 01, AL = 05 |
| | |AAD ; AH = 00, AL = 0Fh (15) |
| | |RET |
|AAM |No operands |ASCII Adjust after Multiplication. |
| | |Corrects the result of multiplication of two BCD |
| | |values. |
| | |Algorithm: |
| | |������ AH = AL / 10 |
| | |������ AL = remainder |
| | |Example: |
| | |MOV AL, 15 ; AL = 0Fh |
| | |AAM ; AH = 01, AL = 05 |
| | |RET |
|AAS |No operands |ASCII Adjust after Subtraction. |
| | |Corrects result in AH and AL after subtraction |
| | |when working with BCD values. |
| | |Algorithm: |
| | |if low nibble of AL > 9 or AF = 1 then: |
| | |������ AL = AL - 6 |
| | |������ AH = AH - 1 |
| | |������ AF = 1 |
| | |������ CF = 1 |
| | |else |
| | |������ AF = 0 |
| | |������ CF = 0 |
| | |in both cases: |
| | |clear the high nibble of AL. |
| | |Example: |
| | |MOV AX, 02FFh ; AH = 02, AL = 0FFh |
| | |AAS ; AH = 01, AL = 09 |
| | |RET |
|ADC |REG, memory |Add with Carry. |
| |memory, REG |Algorithm: |
| |REG, REG |operand1 = operand1 + operand2 + CF |
| |memory, immediate |Example: |
| |REG, immediate |STC ; set CF = 1 |
| | |MOV AL, 5 ; AL = 5 |
| | |ADC AL, 1 ; AL = 7 |
| | |RET |
|ADD |REG, memory |Add. |
| |memory, REG |Algorithm: |
| |REG, REG |operand1 = operand1 + operand2 |
| |memory, immediate |Example: |
| |REG, immediate |MOV AL, 5 ; AL = 5 |
| | |ADD AL, -3 ; AL = 2 |
| | |RET |
|AND |REG, memory |Logical AND between all bits of two operands. |
| |memory, REG |Result is stored in operand1. |
| |REG, REG |These rules apply: |
| |memory, immediate |1 AND 1 = 1 |
| |REG, immediate |1 AND 0 = 0 |
| | |0 AND 1 = 0 |
| | |0 AND 0 = 0 |
| | |Example: |
| | |MOV AL, 'a' ; AL = 01100001b |
| | |AND AL, 11011111b ; AL = 01000001b ('A') |
| | |RET |
|CALL |procedure name |Transfers control to procedure, return address is |
| |label |(IP) is pushed to stack. 4-byte address may be |
| |4-byte address |entered in this form: 1234h:5678h, first value is segment second value is an offset (this |
| | |is a far |
| | |Call, so CS is also pushed to stack). |
| | |Example: |
| | |ORG 100h ; for COM file. |
| | |CALL p1 |
| | |ADD AX, 1 |
| | |RET ; return to OS. |
| | |p1 PROC ; procedure declaration. |
| | |MOV AX, 1234h |
| | |RET ; return to caller. |
| | |p1 ENDP |
|CBW |No operands |Convert byte into word. |
| | |Algorithm: |
| | |if high bit of AL = 1 then: |
| | |������ AH = 255 (0FFh) |
| | |else |
| | |������ AH = 0 |
| | |Example: |
| | |MOV AX, 0 ; AH = 0, AL = 0 |
| | |MOV AL, -5 ; AX = 000FBh (251) |
| | |CBW ; AX = 0FFFBh (-5) |
| | |RET |
|CLC |No operands |Clear Carry flag. |
| | |Algorithm: |
| | |CF = 0 |
|CLD |No operands |Clear Direction flag. SI and DI will be incremented |
| | |by chain instructions: CMPSB, CMPSW, LODSB, |
| | |LODSW, MOVSB, MOVSW, STOSB, STOSW. |
| | |Algorithm: |
| | |DF = 0 |
|CLI |No operands |Clear Interrupt enable flag. This disables |
| | |hardware interrupts. |
| | |Algorithm: |
| | |IF = 0 |
|CMC |No operands |Complement Carry flag. Inverts value of CF. |
| | |Algorithm: |
| | |if CF = 1 then CF = 0 |
| | |if CF = 0 then CF = 1 |
|CMP |REG, memory |Compare. |
| |memory, REG |Algorithm: |
| |REG, REG |operand1 - operand2 |
| |memory, immediate |result is not stored anywhere, flags are |
| |REG, immediate |set (OF, SF, ZF, AF, PF, CF) according to |
| | |result. |
| | |Example: |
| | |MOV AL, 5 |
| | |MOV BL, 5 |
| | |CMP AL, BL ; AL = 5, ZF = 1 (so equal!) |
| | |RET |
|CMPSB |No operands |Compare bytes: ES:[DI] from DS:[SI]. |
| | |Algorithm: |
| | |������ DS:[SI] - ES:[DI] |
| | |������ set flags according to result: |
| | |OF, SF, ZF, AF, PF, CF |
| | |������ if DF = 0 then |
| | |������ SI = SI + 1 |
| | |������ DI = DI + 1 |
| | |else |
| | |������ SI = SI - 1 |
| | |������ DI = DI - 1 |
|CMPSW |No operands |Compare words: ES:[DI] from DS:[SI]. |
| | |Algorithm: |
| | |������ DS:[SI] - ES:[DI] |
| | |������ set flags according to result: |
| | |OF, SF, ZF, AF, PF, CF |
| | |������ if DF = 0 then |
| | |������ SI = SI + 2 |
| | |������ DI = DI + 2 |
| | |else |
| | |������ SI = SI - 2 |
| | |������ DI = DI - 2 |
|CWD |No operands |Convert Word to Double word. |
| | |Algorithm: |
| | |if high bit of AX = 1 then: |
| | |������ DX = 65535 (0FFFFh) |
| | |else |
| | |������ DX = 0 |
| | |Example: |
| | |MOV DX, 0 ; DX = 0 |
| | |MOV AX, 0 ; AX = 0 |
| | |MOV AX, -5 ; DX AX = 00000h:0FFFBh |
| | |CWD ; DX AX = 0FFFFh:0FFFBh |
| | |RET |
|DAA |No operands |Decimal adjust After Addition. |
| | |Corrects the result of addition of two packed BCD |
| | |values. |
| | |Algorithm: |
| | |if low nibble of AL > 9 or AF = 1 then: |
| | |������ AL = AL + 6 |
| | |������ AF = 1 |
| | |if AL > 9Fh or CF = 1 then: |
| | |������ AL = AL + 60h |
| | |������ CF = 1 |
| | |Example: |
| | |MOV AL, 0Fh ; AL = 0Fh (15) |
| | |DAA ; AL = 15h |
| | |RET |
|DAS |No operands |Decimal adjust After Subtraction. |
| | |Corrects the result of subtraction of two packed |
| | |BCD values. |
| | |Algorithm: |
| | |if low nibble of AL > 9 or AF = 1 then: |
| | |������ AL = AL - 6 |
| | |������ AF = 1 |
| | |if AL > 9Fh or CF = 1 then: |
| | |������ AL = AL - 60h |
| | |������ CF = 1 |
| | |Example: |
| | |MOV AL, 0FFh ; AL = 0FFh (-1) |
| | |DAS ; AL = 99h, CF = 1 |
| | |RET |
|DEC |REG |Decrement. |
| |memory |Algorithm: |
| | |operand = operand - 1 |
| | |Example: |
| | |MOV AL, 255 ; AL = 0FFh (255 or -1) |
| | |DEC AL ; AL = 0FEh (254 or -2) |
| | |RET |
|DIV |REG |Unsigned divide. |
| |memory |Algorithm: |
| | |when operand is a byte: |
| | |AL = AX / operand |
| | |AH = remainder (modulus) |
| | |when operand is a word: |
| | |AX = (DX AX) / operand |
| | |DX = remainder (modulus) |
| | |Example: |
| | |MOV AX, 203 ; AX = 00CBh |
| | |MOV BL, 4 |
| | |DIV BL ; AL = 50 (32h), AH = 3 |
| | |RET |
|HLT |No operands |Halt the System. |
| | |Example: |
| | |MOV AX, 5 |
| | |HLT |
|IDIV |REG |Signed divide. |
| |memory |Algorithm: |
| | |when operand is a byte: |
| | |AL = AX / operand |
| | |AH = remainder (modulus) |
| | |when operand is a word: |
| | |AX = (DX AX) / operand |
| | |DX = remainder (modulus) |
| | |Example: |
| | |MOV AX, -203 ; AX = 0FF35h |
| | |MOV BL, 4 |
| | |IDIV BL ; AL = -50 (0CEh), AH = -3 (0FDh) |
| | |RET |
|IMUL |REG |Signed multiply. |
| |memory |Algorithm: |
| | |when operand is a byte: |
| | |AX = AL * operand. |
| | |when operand is a word: |
| | |(DX AX) = AX * operand. |
| | |Example: |
| | |MOV AL, -2 |
| | |MOV BL, -4 |
| | |IMUL BL ; AX = 8 |
| | |RET |
|IN |AL, im.byte |Input from port into AL or AX. |
| |AL, DX |Second operand is a port number. If required to |
| |AX, im.byte |access port number over 255 - DX register should |
| |AX, DX |be used. |
| | |Example: |
| | |IN AX, 4 ; get status of traffic lights. |
| | |IN AL, 7 ; get status of stepper-motor. |
|INC |REG |Increment. |
| |memory |Algorithm: |
| | |operand = operand + 1 |
| | |Example: |
| | |MOV AL, 4 |
| | |INC AL ; AL = 5 |
| | |RET |
|INT |immediate byte |Interrupt numbered by immediate byte (0..255). |
| | |Algorithm: |
| | |Push to stack: |
| | |������ flags register |
| | |������ CS |
| | |������ IP |
| | |������ IF = 0 |
| | |������ Transfer control to interrupt |
| | |procedure |
| | |Example: |
| | |MOV AH, 0Eh ; teletype. |
| | |MOV AL, 'A' |
| | |INT 10h ; BIOS interrupt. |
| | |RET |
|INTO |No operands |Interrupt 4 if Overflow flag is 1. |
| | |Algorithm: |
| | |if OF = 1 then INT 4 |
| | |Example: |
| | |; -5 - 127 = -132 (not in -128..127) |
| | |; the result of SUB is wrong (124), |
| | |; so OF = 1 is set: |
| | |MOV AL, -5 |
| | |SUB AL, 127 ; AL = 7Ch (124) |
| | |INTO ; process error. |
| | |RET |
|IRET |No operands |Interrupt Return. |
| | |Algorithm: |
| | |Pop from stack: |
| | |������ IP |
| | |������ CS |
| | |������ flags register |
|JA |label |Short Jump if first operand is Above second |
| | |operand (as set by CMP instruction). Unsigned. |
| | |Algorithm: |
| | |if (CF = 0) and (ZF = 0) then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 250 |
| | |CMP AL, 5 |
| | |JA label1 |
| | |PRINT 'AL is not above 5' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is above 5' |
| | |exit: |
| | |RET |
|JAE |label |Short Jump if first operand is Above or Equal to |
| | |second operand (as set by CMP instruction). |
| | |Unsigned. |
| | |Algorithm: |
| | |if CF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 5 |
| | |CMP AL, 5 |
| | |JAE label1 |
| | |PRINT 'AL is not above or equal to 5' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is above or equal to 5' |
| | |exit: |
| | |RET |
|JB |label |Short Jump if first operand is Below second |
| | |operand (as set by CMP instruction). Unsigned. |
| | |Algorithm: |
| | |if CF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 1 |
| | |CMP AL, 5 |
| | |JB label1 |
| | |PRINT 'AL is not below 5' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is below 5' |
| | |exit: |
| | |RET |
|JBE |label |Short Jump if first operand is Below or Equal to |
| | |second operand (as set by CMP instruction). |
| | |Unsigned. |
| | |Algorithm: |
| | |if CF = 1 or ZF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 5 |
| | |CMP AL, 5 |
| | |JBE label1 |
| | |PRINT 'AL is not below or equal to 5' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is below or equal to 5' |
| | |exit: |
| | |RET |
|JC |label |Short Jump if Carry flag is set to 1. |
| | |Algorithm: |
| | |if CF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 255 |
| | |ADD AL, 1 |
| | |JC label1 |
| | |PRINT 'no carry.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'has carry.' |
| | |exit: |
| | |RET |
|JCXZ |label |Short Jump if CX register is 0. |
| | |Algorithm: |
| | |if CX = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV CX, 0 |
| | |JCXZ label1 |
| | |PRINT 'CX is not zero.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'CX is zero.' |
| | |exit: |
| | |RET |
|JE |label |Short Jump if first operand is Equal to second |
| | |operand (as set by CMP instruction). |
| | |Signed/Unsigned. |
| | |Algorithm: |
| | |if ZF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 5 |
| | |CMP AL, 5 |
| | |JE label1 |
| | |PRINT 'AL is not equal to 5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is equal to 5.' |
| | |exit: |
| | |RET |
|JG |label |Short Jump if first operand is Greater then second |
| | |operand (as set by CMP instruction). Signed. |
| | |Algorithm: |
| | |if (ZF = 0) and (SF = OF) then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 5 |
| | |CMP AL, -5 |
| | |JG label1 |
| | |PRINT 'AL is not greater -5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is greater -5.' |
| | |exit: |
| | |RET |
|JGE |label |Short Jump if first operand is Greater or Equal to |
| | |second operand (as set by CMP instruction). |
| | |Signed. |
| | |Algorithm: |
| | |if SF = OF then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 2 |
| | |CMP AL, -5 |
| | |JGE label1 |
| | |PRINT 'AL < -5' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL >= -5' |
| | |exit: |
| | |RET |
|JL |label |Short Jump if first operand is Less then second |
| | |operand (as set by CMP instruction). Signed. |
| | |Algorithm: |
| | |if SF OF then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, -2 |
| | |CMP AL, 5 |
| | |JL label1 |
| | |PRINT 'AL >= 5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL < 5.' |
| | |exit: |
| | |RET |
|JLE |label |Short Jump if first operand is Less or Equal to |
| | |second operand (as set by CMP instruction). |
| | |Signed. |
| | |Algorithm: |
| | |if SF OF or ZF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, -2 |
| | |CMP AL, 5 |
| | |JLE label1 |
| | |PRINT 'AL > 5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL = 5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL < 5.' |
| | |exit: |
| | |RET |
|JNB |label |Short Jump if first operand is Not Below second |
| | |operand (as set by CMP instruction). Unsigned. |
| | |Algorithm: |
| | |if CF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 7 |
| | |CMP AL, 5 |
| | |JNB label1 |
| | |PRINT 'AL < 5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL >= 5.' |
| | |exit: |
| | |RET |
|JNBE |label |Short Jump if first operand is Not Below and Not |
| | |Equal to second operand (as set by CMP |
| | |instruction). Unsigned. |
| | |Algorithm: |
| | |if (CF = 0) and (ZF = 0) then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 7 |
| | |CMP AL, 5 |
| | |JNBE label1 |
| | |PRINT 'AL 5.' |
| | |exit: |
| | |RET |
|JNC |label |Short Jump if Carry flag is set to 0. |
| | |Algorithm: |
| | |if CF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 2 |
| | |ADD AL, 3 |
| | |JNC label1 |
| | |PRINT 'has carry.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'no carry.' |
| | |exit: |
| | |RET |
|JNE |label |Short Jump if first operand is Not Equal to second |
| | |operand (as set by CMP instruction). |
| | |Signed/Unsigned. |
| | |Algorithm: |
| | |if ZF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 2 |
| | |CMP AL, 3 |
| | |JNE label1 |
| | |PRINT 'AL = 3.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'Al 3.' |
| | |exit: |
| | |RET |
|JNG |label |Short Jump if first operand is Not Greater then |
| | |second operand (as set by CMP instruction). |
| | |Signed. |
| | |Algorithm: |
| | |if (ZF = 1) and (SF OF) then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 2 |
| | |CMP AL, 3 |
| | |JNG label1 |
| | |PRINT 'AL > 3.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'Al = 3.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'Al < 3.' |
| | |exit: |
| | |RET |
|JNL |label |Short Jump if first operand is Not Less then |
| | |second operand (as set by CMP instruction). |
| | |Signed. |
| | |Algorithm: |
| | |if SF = OF then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 2 |
| | |CMP AL, -3 |
| | |JNL label1 |
| | |PRINT 'AL < -3.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'Al >= -3.' |
| | |exit: |
| | |RET |
|JNLE |label |Short Jump if first operand is Not Less and Not |
| | |Equal to second operand (as set by CMP |
| | |instruction). Signed. |
| | |Algorithm: |
| | |if (SF = OF) and (ZF = 0) then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 2 |
| | |CMP AL, -3 |
| | |JNLE label1 |
| | |PRINT 'AL -3.' |
| | |exit: |
| | |RET |
|JNO |label |Short Jump if Not Overflow. |
| | |Algorithm: |
| | |if OF = 0 then jump |
| | |Example: |
| | |; -5 - 2 = -7 (inside -128..127) |
| | |; the result of SUB is correct, |
| | |; so OF = 0: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, -5 |
| | |SUB AL, 2 ; AL = 0F9h (-7) |
| | |JNO label1 |
| | |PRINT 'overflow!' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'no overflow.' |
| | |exit: |
| | |RET |
|JNP |label |Short Jump if No Parity (odd). Only 8 low bits of |
| | |result are checked. Set by CMP, SUB, ADD, TEST, |
| | |AND, OR, XOR instructions. |
| | |Algorithm: |
| | |if PF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 00000111b ; AL = 7 |
| | |OR AL, 0 ; just set flags. |
| | |JNP label1 |
| | |PRINT 'parity even.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'parity odd.' |
| | |exit: |
| | |RET |
|JNS |label |Short Jump if Not Signed (if positive). Set by |
| | |CMP, SUB, ADD, TEST, AND, OR, XOR |
| | |instructions. |
| | |Algorithm: |
| | |if SF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 00000111b ; AL = 7 |
| | |OR AL, 0 ; just set flags. |
| | |JNS label1 |
| | |PRINT 'signed.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'not signed.' |
| | |exit: |
| | |RET |
|JNZ |label |Short Jump if Not Zero (not equal). Set by CMP, |
| | |SUB, ADD, TEST, AND, OR, XOR instructions. |
| | |Algorithm: |
| | |if ZF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 00000111b ; AL = 7 |
| | |OR AL, 0 ; just set flags. |
| | |JNZ label1 |
| | |PRINT 'zero.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'not zero.' |
| | |exit: |
| | |RET |
|JO |label |Short Jump if Overflow. |
| | |Algorithm: |
| | |if OF = 1 then jump |
| | |Example: |
| | |; -5 - 127 = -132 (not in -128..127) |
| | |; the result of SUB is wrong (124), |
| | |; so OF = 1 is set: |
| | |include 'emu8086.inc' |
| | |org 100h |
| | |MOV AL, -5 |
| | |SUB AL, 127 ; AL = 7Ch (124) |
| | |JO label1 |
| | |PRINT 'no overflow.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'overflow!' |
| | |exit: |
| | |RET |
|JP |label |Short Jump if Parity (even). Only 8 low bits of |
| | |result are checked. Set by CMP, SUB, ADD, TEST, |
| | |AND, OR, XOR instructions. |
| | |Algorithm: |
| | |if PF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 00000101b ; AL = 5 |
| | |OR AL, 0 ; just set flags. |
| | |JP label1 |
| | |PRINT 'parity odd.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'parity even.' |
| | |exit: |
| | |RET |
|JPE |label |Short Jump if Parity Even. Only 8 low bits of |
| | |result are checked. Set by CMP, SUB, ADD, TEST, |
| | |AND, OR, XOR instructions. |
| | |Algorithm: |
| | |if PF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 00000101b ; AL = 5 |
| | |OR AL, 0 ; just set flags. |
| | |JPE label1 |
| | |PRINT 'parity odd.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'parity even.' |
| | |exit: |
| | |RET |
|JPO |label |Short Jump if Parity Odd. Only 8 low bits of result are checked. Set by CMP, SUB, ADD, |
| | |TEST, AND, |
| | |OR, XOR instructions. |
| | |Algorithm: |
| | |if PF = 0 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 00000111b ; AL = 7 |
| | |OR AL, 0 ; just set flags. |
| | |JPO label1 |
| | |PRINT 'parity even.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'parity odd.' |
| | |exit: |
| | |RET |
|JS |label |Short Jump if Signed (if negative). Set by CMP, |
| | |SUB, ADD, TEST, AND, OR, XOR instructions. |
| | |Algorithm: |
| | |if SF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 10000000b ; AL = -128 |
| | |OR AL, 0 ; just set flags. |
| | |JS label1 |
| | |PRINT 'not signed.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'signed.' |
| | |exit: |
| | |RET |
|JZ |label |Short Jump if Zero (equal). Set by CMP, SUB, |
| | |ADD, TEST, AND, OR, XOR instructions. |
| | |Algorithm: |
| | |if ZF = 1 then jump |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AL, 5 |
| | |CMP AL, 5 |
| | |JZ label1 |
| | |PRINT 'AL is not equal to 5.' |
| | |JMP exit |
| | |label1: |
| | |PRINT 'AL is equal to 5.' |
| | |exit: |
| | |RET |
|LAHF |No operands |Load AH from 8 low bits of Flags register. |
| | |Algorithm: |
| | |AH = flags register |
| | |AH bit: 7 6 5 4 3 2 1 0 |
| | |[SF] [ZF] [0] [AF] [0] [PF] [1] [CF] |
| | |bits 1, 3, 5 are reserved. |
|LDS |REG, memory |Load memory double word into word register and DS. |
| | |Algorithm: |
| | |������ REG = first word |
| | |������ DS = second word |
| | |Example: |
| | |ORG 100h |
| | |LDS AX, m |
| | |RET |
| | |m DW 1234h |
| | |DW 5678h |
| | |END |
| | |AX is set to 1234h, DS is set to 5678h. |
|LEA |REG, memory |Load Effective Address. |
| | |Algorithm: |
| | |������ REG = address of memory (offset) |
| | |Example: |
| | |MOV BX, 35h |
| | |MOV DI, 12h |
| | |LEA SI, [BX+DI] ; SI = 35h + 12h = 47h |
| | |Note: The integrated 8086 assembler |
| | |automatically replaces LEA with a more efficient |
| | |MOV where possible. For example: |
| | |org 100h |
| | |LEA AX, m ; AX = offset of m |
| | |RET |
| | |m dw 1234h |
| | |END |
|LES |REG, memory |Load memory double word into word register and ES. |
| | |Algorithm: |
| | |������ REG = first word |
| | |������ ES = second word |
| | |Example: |
| | |ORG 100h |
| | |LES AX, m |
| | |RET |
| | |m DW 1234h |
| | |DW 5678h |
| | |END |
| | |AX is set to 1234h, ES is set to 5678h. |
|LODSB |No operands |Load byte at DS:[SI] into AL. Update SI. |
| | |Algorithm: |
| | |������ AL = DS:[SI] |
| | |������ if DF = 0 then |
| | |������ SI = SI + 1 |
| | |else |
| | |������ SI = SI - 1 |
| | |Example: |
| | |ORG 100h |
| | |LEA SI, a1 |
| | |MOV CX, 5 |
| | |MOV AH, 0Eh |
| | |m: LODSB |
| | |INT 10h |
| | |LOOP m |
| | |RET |
| | |a1 DB 'H', 'e', 'l', 'l', 'o' |
|LODSW |No operands |Load word at DS:[SI] into AX. Update SI. |
| | |Algorithm: |
| | |������ AX = DS:[SI] |
| | |������ if DF = 0 then |
| | |������ SI = SI + 2 |
| | |else |
| | |������ SI = SI - 2 |
| | |Example: |
| | |ORG 100h |
| | |LEA SI, a1 |
| | |MOV CX, 5 |
| | |REP LODSW ; finally there will be 555h in AX. |
| | |RET |
| | |a1 dw 111h, 222h, 333h, 444h, 555h |
|LOOP |label |Decrease CX, jump to label if CX not zero. |
| | |Algorithm: |
| | |������ CX = CX - 1 |
| | |������ if CX 0 then |
| | |������ jump |
| | |else |
| | |������ no jump, continue |
| | |Example: |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV CX, 5 |
| | |label1: |
| | |PRINTN 'loop!' |
| | |LOOP label1 |
| | |RET |
|LOOPE |label |Decrease CX, jump to label if CX not zero and |
| | |Equal (ZF = 1). |
| | |Algorithm: |
| | |������ CX = CX - 1 |
| | |������ if (CX 0) and (ZF = 1) then |
| | |������ jump |
| | |else |
| | |������ no jump, continue |
| | |Example: |
| | |; Loop until result fits into AL alone, |
| | |; or 5 times. The result will be over 255 |
| | |; on third loop (100+100+100), |
| | |; so loop will exit. |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AX, 0 |
| | |MOV CX, 5 |
| | |label1: |
| | |PUTC '*' |
| | |ADD AX, 100 |
| | |CMP AH, 0 |
| | |LOOPE label1 |
| | |RET |
|LOOPNE |label |Decrease CX, jump to label if CX not zero and Not |
| | |Equal (ZF = 0). |
| | |Algorithm: |
| | |������ CX = CX - 1 |
| | |������ if (CX 0) and (ZF = 0) then |
| | |������ jump |
| | |else |
| | |������ no jump, continue |
| | |Example: |
| | |; Loop until '7' is found, |
| | |; or 5 times. |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV SI, 0 |
| | |MOV CX, 5 |
| | |label1: |
| | |PUTC '*' |
| | |MOV AL, v1[SI] |
| | |INC SI ; next byte (SI=SI+1). |
| | |CMP AL, 7 |
| | |LOOPNE label1 |
| | |RET |
| | |v1 db 9, 8, 7, 6, 5 |
|LOOPNZ |label |Decrease CX, jump to label if CX not zero and ZF |
| | |= 0. |
| | |Algorithm: |
| | |������ CX = CX - 1 |
| | |������ if (CX 0) and (ZF = 0) then |
| | |������ jump |
| | |else |
| | |������ no jump, continue |
| | |Example: |
| | |; Loop until '7' is found, |
| | |; or 5 times. |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV SI, 0 |
| | |MOV CX, 5 |
| | |label1: |
| | |PUTC '*' |
| | |MOV AL, v1[SI] |
| | |INC SI ; next byte (SI=SI+1). |
| | |CMP AL, 7 |
| | |LOOPNZ label1 |
| | |RET |
| | |v1 db 9, 8, 7, 6, 5 |
|LOOPZ |label |Decrease CX, jump to label if CX not zero and ZF |
| | |= 1. |
| | |Algorithm: |
| | |������ CX = CX – 1 |
| | |������ if (CX 0) and (ZF = 1) then |
| | |������ jump |
| | |else |
| | |������ no jump, continue |
| | |Example: |
| | |; Loop until result fits into AL alone, |
| | |; or 5 times. The result will be over 255 |
| | |; on third loop (100+100+100), |
| | |; so loop will exit. |
| | |include 'emu8086.inc' |
| | |ORG 100h |
| | |MOV AX, 0 |
| | |MOV CX, 5 |
| | |label1: |
| | |PUTC '*' |
| | |ADD AX, 100 |
| | |CMP AH, 0 |
| | |LOOPZ label1 |
| | |RET |
|MOV |REG, memory |Copy operand2 to operand1. |
| |memory, REG |The MOV instruction cannot: |
| |REG, REG |������ set the value of the CS and IP registers. |
| |memory, immediate |������ copy value of one segment register to |
| |REG, immediate |another segment register (should copy to |
| |SREG, memory |general register first). |
| |memory, SREG |������ copy immediate value to segment register |
| |REG, SREG |(should copy to general register first). |
| |SREG, REG |Algorithm: |
| | |operand1 = operand2 |
| | |Example: |
| | |ORG 100h |
| | |MOV AX, 0B800h ; set AX = B800h (VGA memory). |
| | |MOV DS, AX ; copy value of AX to DS. |
| | |MOV CL, 'A' ; CL = 41h (ASCII code). |
| | |MOV CH, 01011111b ; CL = color attribute. |
| | |MOV BX, 15Eh ; BX = position on screen. |
| | |MOV [BX], CX ; w.[0B800h:015Eh] = CX. |
| | |RET ; returns to operating system. |
|MOVSB |No operands |Copy byte at DS:[SI] to ES:[DI]. Update SI and |
| | |DI. |
| | |Algorithm: |
| | |������ ES:[DI] = DS:[SI] |
| | |������ if DF = 0 then |
| | |������ SI = SI + 1 |
| | |������ DI = DI + 1 |
| | |else |
| | |������ SI = SI - 1 |
| | |������ DI = DI - 1 |
| | |Example: |
| | |ORG 100h |
| | |CLD |
| | |LEA SI, a1 |
| | |LEA DI, a2 |
| | |MOV CX, 5 |
| | |REP MOVSB |
| | |RET |
| | |a1 DB 1,2,3,4,5 |
| | |a2 DB 5 DUP(0) |
|MOVSW |No operands |Copy word at DS:[SI] to ES:[DI]. Update SI and |
| | |DI. |
| | |Algorithm: |
| | |������ ES:[DI] = DS:[SI] |
| | |������ if DF = 0 then |
| | |������ SI = SI + 2 |
| | |������ DI = DI + 2 |
| | |else |
| | |������ SI = SI - 2 |
| | |������ DI = DI - 2 |
| | |Example: |
| | |ORG 100h |
| | |CLD |
| | |LEA SI, a1 |
| | |LEA DI, a2 |
| | |MOV CX, 5 |
| | |REP MOVSW |
| | |RET |
| | |a1 DW 1,2,3,4,5 |
| | |a2 DW 5 DUP(0) |
|MUL |REG memory |Unsigned multiply. |
| | |Algorithm: |
| | |when operand is a byte: |
| | |AX = AL * operand. |
| | |when operand is a word: |
| | |(DX AX) = AX * operand. |
| | |Example: |
| | |MOV AL, 200 ; AL = 0C8h |
| | |MOV BL, 4 |
| | |MUL BL ; AX = 0320h (800) |
| | |RET |
|NEG |REG |Negate. Makes operand negative (two's |
| |memory |complement). |
| | |Algorithm: |
| | |������ Invert all bits of the operand |
| | |������ Add 1 to inverted operand |
| | |Example: |
| | |MOV AL, 5 ; AL = 05h |
| | |NEG AL ; AL = 0FBh (-5) |
| | |NEG AL ; AL = 05h (5) |
| | |RET |
|NOP |No operands |No Operation. |
| | |Algorithm: |
| | |������ Do nothing |
| | |Example: |
| | |; do nothing, 3 times: |
| | |NOP |
| | |NOP |
| | |NOP |
| | |RET |
|NOT |REG |Invert each bit of the operand. |
| |memory |Algorithm: |
| | |������ if bit is 1 turn it to 0. |
| | |������ if bit is 0 turn it to 1. |
| | |Example: |
| | |MOV AL, 00011011b |
| | |NOT AL ; AL = 11100100b |
| | |RET |
|OR |REG, memory |Logical OR between all bits of two operands. |
| |memory, REG |Result is stored in first operand. |
| |REG, REG |These rules apply: |
| |memory, immediate |1 OR 1 = 1 |
| |REG, immediate |1 OR 0 = 1 |
| | |0 OR 1 = 1 |
| | |0 OR 0 = 0 |
| | |Example: |
| | |MOV AL, 'A' ; AL = 01000001b |
| | |OR AL, 00100000b ; AL = 01100001b ('a') |
| | |RET |
|OUT |im.byte, AL |Output from AL or AX to port. |
| |im.byte, AX |First operand is a port number. If required to |
| |DX, AL |access port number over 255 - DX register should |
| |DX, AX |be used. |
| | |Example: |
| | |MOV AX, 0FFFh ; Turn on all |
| | |OUT 4, AX ; traffic lights. |
| | |MOV AL, 100b ; Turn on the third |
| | |OUT 7, AL ; magnet of the stepper-motor. |
|POP |REG |Get 16 bit value from the stack. |
| |SREG |Algorithm: |
| |memory |������ operand = SS:[SP] (top of the stack) |
| | |������ SP = SP + 2 |
| | |Example: |
| | |MOV AX, 1234h |
| | |PUSH AX |
| | |POP DX ; DX = 1234h |
| | |RET |
|POPA |No operands |Pop all general purpose registers DI, SI, BP, SP, |
| | |BX, DX, CX, AX from the stack. SP value is ignored, it is Popped but not set to SP |
| | |register). |
| | |Note: this instruction works only on 80186 CPU |
| | |and later! |
| | |Algorithm: |
| | |������ POP DI |
| | |������ POP SI |
| | |������ POP BP |
| | |������ POP xx (SP value ignored) |
| | |������ POP BX |
| | |������ POP DX |
| | |������ POP CX |
| | |������ POP AX |
|POPF |No operands |Get flags register from the stack. |
| | |Algorithm: |
| | |������ flags = SS:[SP] (top of the stack) |
| | |������ SP = SP + 2 |
|PUSH |REG |Store 16 bit value in the stack. |
| |SREG |Note: PUSH immediate works only on 80186 |
| |memory |CPU and later! |
| |immediate |Algorithm: |
| | |������ SP = SP - 2 |
| | |������ SS:[SP] (top of the stack) = operand |
| | |Example: |
| | |MOV AX, 1234h |
| | |PUSH AX |
| | |POP DX ; DX = 1234h |
| | |RET |
|PUSHA |No operands |Push all general purpose registers AX, CX, DX, |
| | |BX, SP, BP, SI, DI in the stack. |
| | |Original value of SP register (before PUSHA) is |
| | |used. |
| | |Note: this instruction works only on 80186 CPU |
| | |and later! |
| | |Algorithm: |
| | |������ PUSH AX |
| | |������ PUSH CX |
| | |������ PUSH DX |
| | |������ PUSH BX |
| | |������ PUSH SP |
| | |������ PUSH BP |
| | |������ PUSH SI |
| | |������ PUSH DI |
|PUSHF |No operands |Store flags register in the stack. |
| | |Algorithm: |
| | |������ SP = SP - 2 |
| | |������ SS:[SP] (top of the stack) = flags |
|RCL |memory, immediate |Rotate operand1 left through Carry Flag. The |
| |REG, immediate |number of rotates is set by operand2. |
| |memory, CL |When immediate is greater then 1, assembler |
| |REG, CL |generates several RCL xx, 1 instructions because |
| | |8086 has machine code only for this instruction |
| | |(the same principle works for all other shift/rotate |
| | |instructions). |
| | |Algorithm: |
| | |shift all bits left, the bit that goes |
| | |off is set to CF and previous value of |
| | |CF is inserted to the right-most |
| | |position. |
| | |Example: |
| | |STC ; set carry (CF=1). |
| | |MOV AL, 1Ch ; AL = 00011100b |
| | |RCL AL, 1 ; AL = 00111001b, CF=0. |
| | |RET |
|RCR |memory, immediate |Rotate operand1 right through Carry Flag. The |
| |REG, immediate |number of rotates is set by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |shift all bits right, the bit that |
| | |goes off is set to CF and previous |
| | |value of CF is inserted to the leftmost |
| | |position. |
| | |Example: |
| | |STC ; set carry (CF=1). |
| | |MOV AL, 1Ch ; AL = 00011100b |
| | |RCR AL, 1 ; AL = 10001110b, CF=0. |
| | |RET |
|REP |chain instruction |Repeat following MOVSB, MOVSW, LODSB, |
| | |LODSW, STOSB, STOSW instructions CX times. |
| | |Algorithm: |
| | |check_cx: |
| | |if CX 0 then |
| | |������ do following chain instruction |
| | |������ CX = CX - 1 |
| | |������ go back to check_cx |
| | |else |
| | |������ exit from REP cycle |
|REPE |chain instruction |Repeat following CMPSB, CMPSW, SCASB, SCASW |
| | |instructions while ZF = 1 (result is Equal), |
| | |maximum CX times. |
| | |Algorithm: |
| | |check_cx: |
| | |if CX 0 then |
| | |������ do following chain instruction |
| | |������ CX = CX - 1 |
| | |������ if ZF = 1 then: |
| | |������ go back to check_cx |
| | |else |
| | |������ exit from REPE cycle |
| | |else |
| | |������ exit from REPE cycle |
|REPNE |chain instruction |Repeat following CMPSB, CMPSW, SCASB, SCASW |
| | |instructions while ZF = 0 (result is Not Equal), |
| | |maximum CX times. |
| | |Algorithm: |
| | |check_cx: |
| | |if CX 0 then |
| | |������ do following chain instruction |
| | |������ CX = CX - 1 |
| | |������ if ZF = 0 then: |
| | |������ go back to check_cx |
| | |else |
| | |������ exit from REPNE cycle |
| | |else |
| | |������ exit from REPNE cycle |
|REPNZ |chain instruction |Repeat following CMPSB, CMPSW, SCASB, SCASW |
| | |instructions while ZF = 0 (result is Not Zero), |
| | |maximum CX times. |
| | |Algorithm: |
| | |check_cx: |
| | |if CX 0 then |
| | |������ do following chain instruction |
| | |������ CX = CX - 1 |
| | |������ if ZF = 0 then: |
| | |������ go back to check_cx |
| | |else |
| | |������ exit from REPNZ cycle |
| | |else |
| | |������ exit from REPNZ cycle |
|REPZ |chain instruction |Repeat following CMPSB, CMPSW, SCASB, SCASW |
| | |instructions while ZF = 1 (result is Zero), |
| | |maximum CX times. |
| | |Algorithm: |
| | |check_cx: |
| | |if CX 0 then |
| | |������ do following chain instruction |
| | |������ CX = CX - 1 |
| | |������ if ZF = 1 then: |
| | |������ go back to check_cx |
| | |else |
| | |������ exit from REPZ cycle |
| | |else |
| | |������ exit from REPZ cycle |
|RET |No operands |Return from near procedure. |
| |or even immediate |Algorithm: |
| | |������ Pop from stack: |
| | |������ IP |
| | |������ if immediate operand is present: |
| | |SP = SP + operand |
| | |Example: |
| | |ORG 100h ; for COM file. |
| | |CALL p1 |
| | |ADD AX, 1 |
| | |RET ; return to OS. |
| | |p1 PROC ; procedure declaration. |
| | |MOV AX, 1234h |
| | |RET ; return to caller. |
| | |p1 ENDP |
|RETF |No operands |Return from Far procedure. |
| |or even immediate |Algorithm: |
| | |������ Pop from stack: |
| | |������ IP |
| | |������ CS |
| | |������ if immediate operand is present: |
| | |SP = SP + operand |
|ROL |memory, immediate |Rotate operand1 left. The number of rotates is set |
| |REG, immediate |by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |shift all bits left, the bit that goes |
| | |off is set to CF and the same bit is |
| | |inserted to the right-most position. |
| | |Example: |
| | |MOV AL, 1Ch ; AL = 00011100b |
| | |ROL AL, 1 ; AL = 00111000b, CF=0. |
| | |RET |
|ROR |memory, immediate |Rotate operand1 right. The number of rotates is |
| |REG, immediate |set by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |shift all bits right, the bit that |
| | |goes off is set to CF and the same bit |
| | |is inserted to the left-most position. |
| | |Example: |
| | |MOV AL, 1Ch ; AL = 00011100b |
| | |ROR AL, 1 ; AL = 00001110b, CF=0. |
| | |RET |
|SAHF |No operands |Store AH register into low 8 bits of Flags register. |
| | |Algorithm: |
| | |flags register = AH |
| | |AH bit: 7 6 5 4 3 2 1 0 |
| | |[SF] [ZF] [0] [AF] [0] [PF] [1] [CF] |
| | |bits 1, 3, 5 are reserved. |
|SAL |memory, immediate |Shift Arithmetic operand1 Left. The number of |
| |REG, immediate |shifts is set by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |������ Shift all bits left, the bit that goes |
| | |off is set to CF. |
| | |������ Zero bit is inserted to the right-most |
| | |position. |
| | |Example: |
| | |MOV AL, 0E0h ; AL = 11100000b |
| | |SAL AL, 1 ; AL = 11000000b, CF=1. |
| | |RET |
|SAR |memory, immediate |Shift Arithmetic operand1 Right. The number of |
| |REG, immediate |shifts is set by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |������ Shift all bits right, the bit that |
| | |goes off is set to CF. |
| | |������ The sign bit that is inserted to the |
| | |left-most position has the same value |
| | |as before shift. |
| | |Example: |
| | |MOV AL, 0E0h ; AL = 11100000b |
| | |SAR AL, 1 ; AL = 11110000b, CF=0. |
| | |MOV BL, 4Ch ; BL = 01001100b |
| | |SAR BL, 1 ; BL = 00100110b, CF=0. |
| | |RET |
|SBB |REG, memory |Subtract with Borrow. |
| |memory, REG |Algorithm: |
| |REG, REG |operand1 = operand1 - operand2 - CF |
| |memory, immediate |Example: |
| |REG, immediate |STC |
| | |MOV AL, 5 |
| | |SBB AL, 3 ; AL = 5 - 3 - 1 = 1 |
| | |RET |
|SCASB |No operands |Compare bytes: AL from ES:[DI]. |
| | |Algorithm: |
| | |������ AL - ES:[DI] |
| | |������ set flags according to result: |
| | |OF, SF, ZF, AF, PF, CF |
| | |������ if DF = 0 then |
| | |������ DI = DI + 1 |
| | |else |
| | |������ DI = DI - 1 |
|SCASW |No operands |Compare words: AX from ES:[DI]. |
| | |Algorithm: |
| | |������ AX - ES:[DI] |
| | |������ set flags according to result: |
| | |OF, SF, ZF, AF, PF, CF |
| | |������ if DF = 0 then |
| | |������ DI = DI + 2 |
| | |else |
| | |������ DI = DI - 2 |
|SHL |memory, immediate |Shift operand1 Left. The number of shifts is set |
| |REG, immediate |by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |������ Shift all bits left, the bit that goes |
| | |off is set to CF. |
| | |������ Zero bit is inserted to the right-most |
| | |position. |
| | |Example: |
| | |MOV AL, 11100000b |
| | |SHL AL, 1 ; AL = 11000000b, CF=1. |
| | |RET |
|SHR |memory, immediate |Shift operand1 Right. The number of shifts is set |
| |REG, immediate |by operand2. |
| |memory, CL |Algorithm: |
| |REG, CL |������ Shift all bits right, the bit that |
| | |goes off is set to CF. |
| | |������ Zero bit is inserted to the left-most |
| | |position. |
| | |Example: |
| | |MOV AL, 00000111b |
| | |SHR AL, 1 ; AL = 00000011b, CF=1. |
| | |RET |
|STC |No operands |Set Carry flag. |
| | |Algorithm: |
| | |CF = 1 |
|STD |No operands |Set Direction flag. SI and DI will be decremented |
| | |by chain instructions: CMPSB, CMPSW, LODSB, |
| | |LODSW, MOVSB, MOVSW, STOSB, STOSW. |
| | |Algorithm: |
| | |DF = 1 |
|STI |No operands |Set Interrupt enable flag. This enables hardware |
| | |interrupts. |
| | |Algorithm: |
| | |IF = 1 |
|STOSB |No operands |Store byte in AL into ES:[DI]. Update DI. |
| | |Algorithm: |
| | |������ ES:[DI] = AL |
| | |������ if DF = 0 then |
| | |������ DI = DI + 1 |
| | |else |
| | |������ DI = DI - 1 |
| | |Example: |
| | |ORG 100h |
| | |LEA DI, a1 |
| | |MOV AL, 12h |
| | |MOV CX, 5 |
| | |REP STOSB |
| | |RET |
| | |a1 DB 5 dup(0) |
|STOSW |No operands |Store word in AX into ES:[DI]. Update DI. |
| | |Algorithm: |
| | |������ ES:[DI] = AX |
| | |������ if DF = 0 then |
| | |������ DI = DI + 2 |
| | |else |
| | |������ DI = DI - 2 |
| | |Example: |
| | |ORG 100h |
| | |LEA DI, a1 |
| | |MOV AX, 1234h |
| | |MOV CX, 5 |
| | |REP STOSW |
| | |RET |
| | |a1 DW 5 dup(0) |
|SUB |REG, memory |Subtract. |
| |memory, REG |Algorithm: |
| |REG, REG |operand1 = operand1 - operand2 |
| |memory, immediate |Example: |
| |REG, immediate |MOV AL, 5 |
| | |SUB AL, 1 ; AL = 4 |
| | |RET |
|TEST |REG, memory |Logical AND between all bits of two operands for |
| |memory, REG |flags only. These flags are effected: ZF, SF, PF. |
| |REG, REG |Result is not stored anywhere. |
| |memory, immediate |These rules apply: |
| |REG, immediate |1 AND 1 = 1 |
| | |1 AND 0 = 0 |
| | |0 AND 1 = 0 |
| | |0 AND 0 = 0 |
| | |Example: |
| | |MOV AL, 00000101b |
| | |TEST AL, 1 ; ZF = 0. |
| | |TEST AL, 10b ; ZF = 1. |
| | |RET |
|XCHG |REG, memory |Exchange values of two operands. |
| |memory, REG |Algorithm: |
| |REG, REG |operand1 < - > operand2 |
| | |Example: |
| | |MOV AL, 5 |
| | |MOV AH, 2 |
| | |XCHG AL, AH ; AL = 2, AH = 5 |
| | |XCHG AL, AH ; AL = 5, AH = 2 |
| | |RET |
|XLATB |No operands |Translate byte from table. |
| | |Copy value of memory byte at |
| | |DS:[BX + unsigned AL] to AL register. |
| | |Algorithm: |
| | |AL = DS:[BX + unsigned AL] |
| | |Example: |
| | |ORG 100h |
| | |LEA BX, dat |
| | |MOV AL, 2 |
| | |XLATB ; AL = 33h |
| | |RET |
|XOR |REG, memory |Logical XOR (Exclusive OR) between all bits of |
| |memory, REG |two operands. Result is stored in first operand. |
| |REG, REG |These rules apply: |
| |memory, immediate |1 XOR 1 = 0 |
| |REG, immediate |1 XOR 0 = 1 |
| | |0 XOR 1 = 1 |
| | |0 XOR 0 = 0 |
| | |Example: |
| | |MOV AL, 00000111b |
| | |XOR AL, 00000010b ; AL = 00000101b |
| | |RET |