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Catalog / Assembly Language Cheat Sheet

Assembly Language Cheat Sheet

A quick reference for Assembly Language syntax, instructions, and concepts. Covers basic instructions, addressing modes, and common programming constructs.

Basic Instructions

Data Transfer Instructions

MOV

Move data from one location to another.

Example:

MOV destination, source

LEA

Load Effective Address. Loads the address of the source operand into the destination operand.

Example:

LEA destination, source

PUSH

Push data onto the stack.

Example:

PUSH source

POP

Pop data from the stack.

Example:

POP destination

XCHG

Exchange the contents of two operands.

Example:

XCHG operand1, operand2

Arithmetic Instructions

ADD

Add two operands.

Example:

ADD destination, source

SUB

Subtract two operands.

Example:

SUB destination, source

MUL

Multiply two operands.

Example:

MUL source

DIV

Divide two operands.

Example:

DIV source

INC

Increment operand by 1.

Example:

INC destination

DEC

Decrement operand by 1.

Example:

DEC destination

Logical Instructions

AND

Bitwise AND operation.

Example:

AND destination, source

OR

Bitwise OR operation.

Example:

OR destination, source

XOR

Bitwise XOR operation.

Example:

XOR destination, source

NOT

Bitwise NOT operation.

Example:

NOT destination

SHL / SAL

Shift Left / Shift Arithmetic Left.

Example:

SHL destination, count

SHR / SAR

Shift Right / Shift Arithmetic Right.

Example:

SHR destination, count

ROL

Rotate Left.

Example:

ROL destination, count

ROR

Rotate Right.

Example:

ROR destination, count

Control Flow

Comparison and Jump Instructions

CMP

Compare two operands (affects flags).

Example:

CMP operand1, operand2

JE / JZ

Jump if Equal / Jump if Zero.

Example:

JE label

JNE / JNZ

Jump if Not Equal / Jump if Not Zero.

Example:

JNE label

JG / JNLE

Jump if Greater / Jump if Not Less or Equal.

Example:

JG label

JL / JNGE

Jump if Less / Jump if Not Greater or Equal.

Example:
JL label

JGE / JNL

Jump if Greater or Equal / Jump if Not Less.

Example:
JGE label

JLE / JNG

Jump if Less or Equal / Jump if Not Greater.

Example:
JLE label

JMP

Unconditional jump.

Example:

JMP label

Looping

LOOP

Decrement CX and jump to label if CX != 0.

Example:

MOV CX, 10 ; Set loop counter
loop_start:
  ; ... loop body ...
  LOOP loop_start

Subroutines (Functions)

CALL

Call a subroutine. Pushes the return address onto the stack and jumps to the subroutine.

Example:

CALL subroutine_name

RET

Return from a subroutine. Pops the return address from the stack and jumps to it.

Example:

RET

Addressing Modes

Addressing Modes

Immediate Addressing: Operand is a constant value.

Example:

MOV AX, 10  ; Move the value 10 into register AX

Register Addressing: Operand is a register.

Example:

MOV AX, BX  ; Move the value in register BX to register AX

Direct Addressing: Operand is a memory address.

Example:

MOV AX, [1000]  ; Move the value at memory address 1000 into register AX

Indirect Addressing: Operand is a register that contains the memory address.

Example:

MOV AX, [BX]  ; Move the value at the memory address stored in register BX into register AX

Base-Plus-Index Addressing: Operand is a memory address calculated by adding a base register and an index register.

Example:

MOV AX, [BX + SI] ; Move the value at the memory address (BX + SI) into register AX

Base-Plus-Index with Displacement Addressing: Operand is a memory address calculated by adding a base register, an index register, and a displacement value.

Example:

MOV AX, [BX + SI + 10] ; Move value from memory address (BX + SI + 10) into AX

Data Directives

Data Definition Directives

DB

Define Byte. Allocates one byte of storage.

Example:

my_byte DB 10 ; Defines a byte variable named my_byte with initial value 10

DW

Define Word. Allocates two bytes of storage.

Example:

my_word DW 1000 ; Defines a word variable named my_word with initial value 1000

DD

Define Doubleword. Allocates four bytes of storage.

Example:

my_dword DD 100000 ; Defines a doubleword variable named my_dword with initial value 100000

DQ

Define Quadword. Allocates eight bytes of storage.

Example:

my_qword DQ 100000000 ; Defines a quadword variable named my_qword with initial value 100000000

DT

Define Ten Bytes. Allocates ten bytes of storage.

Example:

my_tenbytes DT 1234567890 ; Defines a ten-byte variable

Other Directives

EQU

Equate. Defines a constant value.

Example:

BUFFER_SIZE EQU 1024 ; Defines a constant BUFFER_SIZE with value 1024

$

Represents the current address of the assembler.

Example:

JMP $ ; creates an infinite loop (jumps to the current instruction)
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