Assembly Commands

DATA TRANSFER SYNTAX

Mov Destination, Source

LDS

Load Data Segment Register

LEA

Load Effective Address

LES

Load Extra Segment Register

LODS

Load String

LSS

Load stack Segment Register

MOV

Move data

MOVS

Move String

MOVSX

Move with sign-extend

MOVZX

Move with Zero-extend

STOS

Store string

XCHG

Exchange

XLAT

Translate

Arithmetic Syntax

Adc destination, source

ADD

add binary number

DEC

Decrement by 1      

DIV

Unsigned Divide  

MUL

Unsigned multiply 

SUB

Subtract binary values

XADD

exchange and add

 ADC:

Add with carry

INC: 

Increment by 1

IDIV

Signed (integer) divide

IMUL

Signed multiply

SBB:

Subtract with borrow

Comparison Syntax

CMP destination, source

CMP:

compare

CMPSn:

Compare string

CMPXCHG:

Compare and exchange

Logical Operator Syntax

AND destination,source

AND:

Logical AND

NOT:

Logical NOT

OR:

Logical OR

XOR:

Exclusive XOR

Input/Output Syntax

OUT destination,source

IN:

Input byte or word

INSn:

Input string

OUT: 

Output byte or word

OUTSn:

Output string

JUMP Syntax

ja label

JA: 

Jump if Above

JAE

Jump if above/equal

JB:

Jump if below

JBE:

Jump if below/equal

JE: 

Jump if Equal

JG:

Jump if Greater

JGE:

Jump if Greater/Equal

JL:

Jump if Less

JNE:

Jump if Not Equal

JNG:

Jump if Not Greater

JNGE:

Jump if Not Greater/Equal

JNL:

Jump if Not Less

JNLE:

JNLE:

JNZ:

Jump if Not Zero

JLE:

Jump if Less/Equal

JNA:

Jump if Not Above

JNB: 

Jump if Not Below

JNBE:

Jump if Not Below/Equal

JZ: 

Jump if Zero

JC:

Jump if Carry

JCXZ:

Jump if CX is Zero

JNO:

Jump if No Overflow

JO:

Jump if Overflow

JNP:

Jump if No Parity

JP/JPO: 

Jump if Parity Odd

JPE:

Jump if Parity Even

JS:

Jump if Sign

JNS:

Jump if No Sign

CALL:

Call a procedure

INT:

Interrupt

IRET: 

Interrupt Return

JMP:

Unconditional Jump

LOOPING Syntax

loop label

LOOP:

Loop until complete

LOOPE:

Loop While Equal

LOOPZ: 

Loop While Zero

LOOPNE: 

Loop While Not Equal

LOOPNZ:

Loop While Not Zero

STACK INSTRUCTIONS Syntax

pop destiny

POP: 

Retrieve the content of the Stack

PUSH:

Store the content of the Stack

POPF:

Pop Flags off the Stack

PUSHF:

Push Flags onto Stack

What is assembly language?

A low-level programming language specific to a processor architecture that uses symbolic codes to represent machine instruction

What converts assembly language into machine code?

An assembler (e.g., NASM, MASM, TASM).

What does the microprocessor handle?

Arithmetic, logical, and control operations.

What are machine language instructions?

Binary instructions (1’s and 0’s) understood directly by the processor.

Why is assembly language used instead of machine language?

It’s easier to read, write, and debug.

What are the three sections of an assembly program?

.data, .bss, and .text

What is the .data section used for?

Declaring initialized data or constants (unchanging data

What is the .bss section used for?

Declaring variables and buffers (zero-filled at runtime).

What is the .text section used for?

Keeping the actual code (instructions).

What must the .text section begin with?

global _start

What symbol begins a comment in assembly?

A semicolon ;

What are the three types of statements in assembly?

• Executable instructions

• Assembler directives (pseudo-ops)

• Macros

What is the syntax format of an assembly statement?

[label] mnemonic [operands] [;comment]

What does the data segment store?

Data elements for the program.

What does the code segment store?

instruction codes.

What does the stack segment store?

Data passed to functions and procedures.

What does a comment do?

It is ignored by the assembler but improves readability.