EAX - 4bytes
AX - 2bytes
AH - 1byte
AL - 1byte
AX=100h*AH+AL

AX	Acumulador
BX	Registro base
CX	Registro contador
DX	Registro de datos
DS	Registro del segmento de datos
ES	Registro del segmento extra
SS	Registro del segmento de pila
CS	Registro del segmento de código
BP	Registro de apuntadores base
SI	Registro índice fuente	DS:SI usado en Strings
DI	Registro índice destino	ES:DI usado en Strings
SP	Registro del apuntador de la pila	SS:SP Indica el último valor de la pila
IP	Registro de apuntador de siguiente instrucción	CS:IP Instruccion siguiente
F	Registro de banderas

Flag		Set	Clear	Negar	Significado
CF	Acarreo	STC	CLC	CMC	Se ha producido acarreo
PF	Paridad				Sumatoria de bits par
AF	Acarreo auxiliar				Acarreo de peso 16
ZF	Cero				Resultado cero
SF	Signo				Bit más significativo
OF	Overflow				Desbordamiento 7fff-8000
TF	Trap o desvío	STI	CLI		Control del flujo
IF	Interrupt	STI	CLI		Interrupciones permitidas
DF	Direction	STD	CLD		Cadenas 0,1=creciante,decreciente

PUSHF - DEC ESP. Puts the flags onto the stack.
POPF - Takes the flags from the stack back off. INC ESP.
LAHF - AH:=FLAGS
SAHF - FLAGS:=AH

ADD, SUB, CMP
CF, PF, AF, ZF, SF, OF

MUL, IMUL
If parte alta mayor que uno -> CF:=1, OF:=1 else ~:=0

DIV, IDIV
Ninguno

INC, DEC
PF, AF, ZF, SF, OF

AND, TEST, OR, XOR
PF, ZF, SF

SHL, SAL
CF, PF, ZF, SF, OF

SHR, SAR
CF, PF, ZF, SF, OF

RCR, RCL
CF, OF
PUSH reg - SUB ESP,bytes. Puts the register onto the stack.
POP reg - Takes the register from the stack back off. ADD ESP,bytes.
PUSHF - SUB ESP,bytes. Puts the flags onto the stack.
POPF - Takes the flags from the stack back off. ADD ESP,bytes. MOV a,b - a:=b
mov AL,byte ptr [SI] - Copy value on direction DS:SI into AL
a:=0 = MOV a,0 = SUB a,a = XOR a,a = AND a,0

Punteros
BX-dirección
[BX]-Valor en dirección BX
mov [BX],AX
mov [CX],AL
mov [AX],WORD PTR [435]
Once again, there are only specific combinations of pointers that can be used. They are:
BX with either SI or DI (but not both)
BP with either SI or DI (but not both)
mov DL, [BX+DI+30]
Interrupt
INT a
Calls a DOS or BIOS function, mainly to do something you would rather not write a function for e.g. change video mode, open a file etc.
a:interrupt
AH:function
NMI - non maskable interrupt : INMEDIATELY
Maskable interrupts : timely fashion
a=0 - divide by zero -----------------------------
a=1 - Trap instruction ---------------------------
a=2 - non_maskable_interrupt (NMI) ---------------
a=3 - 1 byte interrupt for the debugger ----------
a=4 - interrupt on overflow ----------------------
a=5 - imprime el contenido de la pantalla --------
a=8 - actualiza la hora y fecha ------------------
a=9 - provocada al presionar una tecla -----------
a=bh - controla COM1 -----------------------------
a=ch - controla COM2 -----------------------------
a=dh - controla LPT1 -----------------------------
a=eh - controla LPT2 -----------------------------
a=fh - actividad de disco flexible ---------------
a=10h - Video ------------------------------------
00h - set mode, AL=video mode, 3=color 7=mono 13h=graphic
01h - tamaño cursor, CH=parteSuperior CL=parteInferior
02h - posición cursor, BH=página DH=renglón DL=columna
03h - obtener cursor, BH=página pSup->CH pInf->CL fila->DH columna->DL
05h - select active page, AL=página
06h - pantalla haciaarriba, AL=nLineas(0=FULL) BH=atrColor CX=colIni DX=colFin
07h - pantalla a abajo, AL=nLineas(0=FULL) BH=atrColor CX=colIni DX=colFin
08h - lee carácter, BH=página char->AL atrb->AH
09h - desplega char con atr, AL=char BH=page BL=atr CX=nRepeticiones
0ah - desplega char, AL=char BH=page CX=nRepeticiones
0ch - write graphics pixel(XOR) AL=color CX=x DX=y
0eh - printcharacter AL BH=PageNum BL=color1plano lineParametres>[cs:80]
0fh - get current mode ->AL, PageNumber>BH charsperline->AH
11h - Generador de carácter
12h - select panta alterna, {0|1}{color|mono}->BH {0123,64|128|192|256}->BL
bitsAdaptador->CH ConfgConmutación->CL
13h - print chain, [ES:BP]=chain BH=page BL=atr CX=long DX=pantalla AL={0:printNoAvanzaCursor|1:PrtGo|2:pCharThenAtrNoGo|4:pCharThenAtrGo}
a=11h - Determina los dispositivos opcionales ----
AX:=40:10h
a=12h - Tamaño memoria ---------------------------
AX:=tamañoMemoriaTarjeta, 640k=028h
a=13h - E/S Disco --------------------------------
a=14h - Comunicaciones E/S -----------------------
a=15h - Servicios del sistema --------------------
21h - Autoprueba de encendido
43h - Lee el estado del sistema
84h - Da soporte a la palanca de juegos
88h - Determina el tamaño de la memoria extendida
89h - Conmuta el procesador al modo protegido
c2h - Interfaz del ratón
a=16h - Entrada from Keyboard --------------------
00h - getch, SCAN code en AH y ASCII en AL
01h - kbhit (0 si tecla)
a=17h - Salida a impresora -----------------------
a=18h - Entrada al Basic de ROM ------------------
a=19h - Carga el arranque ------------------------
Si un dispositivo de disco esta disponible con los programas de sistema del DOS, lee la pista 0. sector 1. en la localidad de arranque en 7C00H y transfiere el control a esta localidad. Si no existe unidad de disco, transfiere la entrada al BASIC de ROM por medio de la INT 18H. Es posible usar operación como una interrupción de software; no limpia la pantalla o inicializa datos en el BIOS de ROM
a=1ah - Lee y pone la hora -----------------------
00h - CX:DX:=reloj >24h->AL:=>0
01h - reloj:=CX:DX
a=1bh - Toma control en interrupción teclado -----
Ctrl+Break BIOS en ROM transfiera el control a su dirección de interrupción, en donde la bandera este en uno
a=20h - Terminate COM File -----------------------
a=21h - DOS standar interrupt --------------------
01h - al=Getche
02h - putchar DL
05h - print DL
09h - puts (DX=OFFSET stringASCII$,DS=AX=SEG message)
30h - get MS-DOS version (e.g. 4.01,AL=4,AH=01) errors DOS5&HigherSETVER
33h - actual DOS version AL=06h(subfunction) major in BL, minor in BH
3dh - open file, AL=access mode, DS:DX=segment:offset ASCIIZ pathname Handle->AX
3eh - close file, BX=file handle
3fh - read, BX=handle DS:DX=buffer CX=nºbytestoread Éxito->CF=0 ->AX-nºbytesORerrorcode
3ch - create file, CX=fileAttribute, DS:DX=segment:offsetPathname Handle>AX
40h - write, BX=handle DS:DX=buffer CX=nºbytestowrite Éxito->CF=0 ->AX-nºbytesORerrorcode
42h - Posicionarse on file, AL=0|1|2=ini|act|fin CX:DX=desplz unsigned32altaCX BX=handle Éxito->CF=0 PosRespIni->CX:DX Error->CF=1 CodeError->AX
4eh - find first matching file, CX=attributes, DS:DX=segment:offsetPathname CF=0successful [DTA]DiskTransferArea=FindFirstDataBlock
4c00h - Exit to DOS
a=33h - Mouse ------------------------------------
00h - Iniciar, if activado 0->AX else 1->AX
01h - Mostrar
02h - Ocultar
03h - Obtener coordenadas, ¿mov bx,[bp+4]? x->CX y->DX boton->BX
04h - Colocar ratón, CX=x DX=y
05h - Leer Click, BX={0=izq,1=der,2=any} ->if click BX:=0 else BX:=1 x->CX y->DX botón->AX
06h - Botón liberado, BX=bot !pulsado->BX x->CX y->DX button->AX
07h - Fija máximo y mínimo horizontal, CX=max DX=min
08h - Fija máximo y mínimo vertical, CX=max DX=min
09h - Fija el puntero gráfico, BX=max CX=min DX=dir ES=desp
0ah - Atributos ratón en texto, BX=tc CX=c DX=f
0bh - Lee contador de desplazamiento del raton, x->CX y->DX IN al|ax,port_address(0-255) | al|ax,dx(0-65535)
Mueve un byte en dx o pa to al
OUT pa,al|ax | dx,al|ax
Mueve un byte en al to pa
INC reg - reg:=reg+1
DEC reg - reg:=reg-1
ADD a,b - a:=a+b
ADC a,b - a:=a+b+CF(Acarreo)
SUB a,b - a:=a-b
SBB a,b - a:=a-b-CF
CMP reg,val - FLAGS como SUB

a,b pueden ser:
1. two registers
2. a=register, b=variable (memory)
3. a=variable (memory), b=register
4. a=variable (memory), b=constant
5. a=register, b=constant

Se llama complemento a uno de A a NOT A.
Se llama complemento a dos de A a (NOT A)+1, y se lo denomina ( -A ).
a-b = a+(-b) = a+!b+1 MUL a
a(db) - (unsigned int)AX:=(u)AL*(u)a
a(dw) - (unsigned int)DX:AX:=(u)AX*(u)a

a(dd) - (unsigned int)EDX:EAX:=(u)EAX*(u)a

IMUL a
a(db) - (signed int)AX:=(s)AL*(s)a
a(dw) - (signed int)DX:AX:=(s)AX*(s)a

DIV a
db
AL:=(u)AX div (u)a
AH:=(u)AX mod (u)a
dw
AX:=(u)DX:AX div (u)a
DX:=(u)DX:AX mod (u)a

IDIV a
db
AL:=(s)AX div (s)a
AH:=(s)AX mod (s)a
dw
AX:=(s)DX:AX div (s)a
DX:=(s)DX:AX mod (s)a

SHL a,b - Unsigned multiple by two^b - a:=a<<b
SHR a,b - Unsigned divide by two^b - a:=a>>b
SAR a,b - Signed divide by two^b
SAL a,b - same as SHL
Note: The 8086 cannot have the value of opperand2 other than 1. 286/386 cannot have operand2 higher than 31.
Using shifts is a lot faster than using MUL’s and DIV’s.
AND reg,val - reg:=reg & val - {(0,0),(0,1),(1,0),(1,1)}->{0,0,0,1}
OR reg,val - reg:=reg OR val - {(0,0),(0,1),(1,0),(1,1)}->{0,1,1,1}
XOR reg,val - reg:=reg XOR val - {(0,0),(0,1),(1,0),(1,1)}->{0,1,1,0}
NOT reg - reg:=!reg - {0,1}->{1,0}
NEG reg - reg:=-reg = NOT reg + 1 = SUB 0,reg
TEST reg,val - Cambios en FLAGS como AND

A	B	AND	OR	XOR	NOT A
1	1	1	1	0	0
1	0	0	1	1	0
0	1	0	1	1	1
0	0	0	0	0	1

LEA(Load Effective Address) a,b - a:=OFFSET b
OFFSET a - Calcula el offset de a desde el comienzo del segmento (DS)
SEG a - Coge el segmento de a

SEGMENT * 16	| 0 0 1 0	0 1 0 0 1 0 0 1 0 0 1 0	_ _ _ _|	range (0 to 65535) * 16
OFFSET	|_ _ _ _	0 1 0 0 1 0 0 1 0 0 1 0	0 0 1 0 |	range (0 to 65535)
20 bit address	| 0 0 1 0	0 1 0 0 1 0 0 1 0 0 1 0	0 0 1 0 |	range (0 to 1048575) (1 MEG)
DS:SI	======	=======DS======
		======= SI ======	======

JMP a - inconditional jump, SHORT, NEAR or FAR
JA:jumps if the first number was above the second number
JAE,JNC:same as above, but will also jump if they are equal
JB,JC:jumps if the first number was below the second
JBE:same as above, but will also jump if they are equal
JNA:jumps if the first number was NOT above (same as JBE)
JNAE:jumps if the first number was NOT above or the same as (same as JB)
JNB:jumps if the first number was NOT below (same as JAE)
JNBE:jumps if the first number was NOT below or the same as (same as JA)
JZ:jumps if the two numbers were equal
JE:same as JZ, just a different name
JNZ:jumps if the two numbers are NOT equal
JNE:same as above
JCXZ:jump if CX=0

CMP reg,val - FLAGS como SUB RCR a
rotate through carry right
CF:=a.low;a:=a>>1;a.high:=CF
RCL a
CF:=a.hight;a:=a<<1;a.low:=CF
CWD
Convert Word to Doubleword
signed AX to signed DX:AX
CBW
Convert Byte to Word
signed AL to signed AX
CDQ
Convert DoubleWord to QuadWord
signed EAX to signed EDX:EAX
CWDE
Convert Word to Doubleword
signed AX to signed EAX
LOOP label
Using Loop is a better way of making a loop then using JMP’s.
You place the amount of times you want it to loop in the CX register and every time it reackes the loop statement it decrements CX and then does a short jump to the label indicated.
A short jump means that it can only 128 bytes before or 127 bytes after the LOOP instuction.
STOSB/W/D - MOV ES:DI,AL/AX/EAX - apply DF to DI
LODSB/W/D - MOV AL/AX/EAX,DS:SI - apply DF to SI
MOVSB/W/D - MOV ES:DI,DS:SI - apply DF to DI and SI
CMPSB/W/D - CMP DS:SI,ES:DI - apply DFto DI and SI
SCASB/WD - CMP ES:DI,AL/AX/EAX - apply DF to DI
If DF decrece Else crece 1/2/4.

PREFIX
REP STOSB/W/D | LODSB/W/D | ...
REP decrement CX ; repeat if CX is not zero
REPE decrement CX ; repeat if CX not zero and ZF = 1
REPZ decrement CX ; repeat if CX not zero and ZF = 1
REPNE decrement CX ; repeat if CX not zero and ZF = 0
REPNZ decrement CX ; repeat if CX not zero and ZF = 0
CALL a - Calls to procedure a. id. PUSH the following address to the call and JMP a.
RET - Come from the previous CALL. id. POP address and JMP address.
IRET - Return from interrupt

PROC name (NEAR|FAR)
Instructions
. . .
RET
ENDP name
.MODEL MemoryModel

Name	Write Segment						Round Size						16/32 bit
	CS	DS	SS	ES	FS	GS	CS	DS	SS	ES	FS	GS
TINY	yes	no	no	no	no	no	-	-	-	-	-	-	16
SMALL	yes	yes	no	no	no	no	16	-	-	-	-	-	16
MEDIUM	yes	yes	no	no	no	no	16	16	16	-	-	-	16
COMPACT													16
LARGE	yes	yes	no	no	no	no	16	16	16	16	-	-	16
HUGE	yes	yes	no	no	no	no	16	16	16	16	16	-	16
FLAT	yes	yes	no	no	no	no	16	16	16	16	16	16	16
TINY32	yes	no	no	no	no	no	-	-	-	-	-	-	32
SMALL32	yes	yes	no	no	no	no	512	-	-	-	-	-	32
MEDIUM32	yes	yes	no	no	no	no	512	512	512	-	-	-	32
COMPACT32													32
LARGE32	yes	yes	no	no	no	no	512	512	512	512	-	-	32
HUGE32	yes	yes	no	no	no	no	512	512	512	512	512	-	32
FLAT32	yes	yes	no	no	no	no	512	512	512	512	512	512	32
BEX	yes	yes	yes	yes	yes	yes	-	-	-	-	-	-	16
BEX32	yes	yes	yes	yes	yes	yes	-	-	-	-	-	-	32

Macros
Name_of_macro macro (variable0,v1,v2,...)
mov AX,>0 ;Copy variable0 into AX
;;instrucciones
endm

LOCAL a
Declara a como local (e.g. para macros)

DB	define byte	[ 1 byte ]
DW	define word	[ 2 bytes ]
DD	define doubleword	[ 2X2 bytes = 4 bytes ]
DQ	define quadword	[ 4X2 bytes = 8 bytes ]
DT	define ten-byte	[ 10 bytes ]
DF	define farword	[ 6 bytes - used for 80386 only ]

dw 150 dup (400)
The 'dup' is for duplicate. This makes 150 two byte copies and puts the number 400 in each one.
dd 459 dup ( 1, 2, 3, 4, 5 )
This makes 459 copies of what is inside the parentheses. That means ( 5 variables X 4 bytes ) X 459 for a total of 9180 bytes. Starting from the beginning of the array, we will have the sequence: 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3,...
dw 347 dup ( ? )
address_book db 100 dup ( 41 dup (' '))
EQU
= 0023 statement1 EQU 5 * 7
= 0025 statement2 EQU statement1 + 6 - 4
= 000F statement3 EQU statement2 - 22
= 001F statement4 EQU statement3 + 16
= [bp + 3] statement1 EQU [bp + 3]
.exe | .com
.model small
.stack 12h(tamaño)
.data
.code