 section .data
    format db "%d", 0  ; Format specifier for printing integers

section .text
    global _start

    ; Function to calculate the greatest common divisor (GCD)
    GCD:
        mov eax, [esp + 4]  ; Get the first parameter (x)
        mov ebx, [esp + 8]  ; Get the second parameter (y)

        ; Ensure x and y are positive
        test eax, eax
        jge check_y
        neg eax

    check_y:
        test ebx, ebx
        jge gcd_loop
        neg ebx

    gcd_loop:
        ; Calculate remainder (n = x % y)
        mov edx, 0
        mov ecx, ebx
        div ecx  ; EDX:EAX = x / y, remainder in EDX

        ; Update x and y
        mov eax, ebx
        mov ebx, edx

        ; Check if y > 0
        cmp ebx, 0
        jg gcd_loop

        ; Return the result (GCD) in EAX
        ret

    _start:
        ; Call GCD function with different values
        mov edi, 48          ; Value 1
        mov esi, 18          ; Value 2
        call GCD
        push eax
        push format
        call print_result

        ; Call GCD function with different values
        mov edi, 105         ; Value 1
        mov esi, 45          ; Value 2
        call GCD
        push eax
        push format
        call print_result

        ; Exit the program
        mov eax, 1           ; syscall: exit
        xor ebx, ebx         ; status: 0
        int 0x80             ; make system call

    print_result:
        ; Print the result of GCD function
        mov eax, 4           ; syscall: write
        mov ebx, 1           ; file descriptor: STDOUT
        pop edx              ; Pop the format string address
        pop ecx              ; Pop the result (GCD) value
        mov eax, ecx         ; Move GCD value to EAX
        int 0x80             ; make system call
        ret

created 1 year ago

Assembly Online Compiler

Write, Run & Share Assembly code online using OneCompiler's Assembly online compiler for free. It's one of the robust, feature-rich online compilers for Assembly language. Getting started with the OneCompiler's Assembly compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as Assembly and start coding.

About Assembly

Assembly language(asm) is a low-level programming language, where the language instructions will be more similar to machine code instructions.

Every assembler may have it's own assembly language designed for a specific computers or an operating system.

Assembly language requires less execution time and memory. It is more helful for direct hardware manipulation, real-time critical applications. It is used in device drivers, low-level embedded systems etc.

Syntax help

Assembly language usually consists of three sections,

Data section

To initialize variables and constants, buffer size these values doesn't change at runtime.
bss section

To declare variables
text section

_start specifies the starting of this section where the actually code is written.

Variables

There are various define directives to allocate space for variables for both initialized and uninitialized data.

1. To allocate storage space to Initialized data

Syntax

variable-name    define-directive    initial-value

Define Directive	Description	Allocated Space
DB	Define Byte	1 byte
DW	Define Word	2 bytes
DD	Define Doubleword	4 bytes
DQ	Define Quadword	8 bytes
DT	Define Ten Bytes	10 bytes

2. To allocate storage space to un-initialized data

Define Directive	Description
RESB	Reserve a Byte
RESW	Reserve a Word
RESD	Reserve a Doubleword
RESQ	Reserve a Quadword
REST	Reserve a Ten Bytes

Constants

Constants can be defined using

1. equ

To define numeric constants

CONSTANT_NAME EQU regular-exp or value

2. %assign

To define numeric constants.

%assign constant_name value

3. %define

To define numeric or string constants.

%define constant_name value

Loops

Loops are used to iterate a set of statements for a specific number of times.

mov ECX,n
L1:
;<loop body>
loop L1

where n specifies the no of times loops should iterate.

Procedures

Procedure is a sub-routine which contains set of statements. Usually procedures are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

procedure_name:
   ;procedure body
   ret