 section .data
	hello:     db 'Hello world!',10    ; 'Hello world!' plus a linefeed character
	helloLen:  equ $-hello             ; Length of the 'Hello world!' string

section .text
	global _start

_start:
#    endbr64
    push   rbp
    mov    rbp,rsp
    sub    rsp,0x40
    movabs rax,0x54454d4f434c4557
    movabs rdx,0x414e4f5a4952414f
    mov    QWORD PTR [rbp-0x40],rax
    mov    QWORD PTR [rbp-0x38],rdx
    movabs rax,0x494e554554415453
    movabs rdx,0x59544953524556
    mov    QWORD PTR [rbp-0x30],rax
    mov    QWORD PTR [rbp-0x28],rdx
    mov    QWORD PTR [rbp-0x20],0x0
    lea    rax,[rbp-0x40]
    mov    rdi,rax
 #   call   0x1080 <strlen@plt>
    mov    DWORD PTR [rbp-0xc],eax
    mov    DWORD PTR [rbp-0x8],0x0
    jmp    0x121e <caesar+149>
    mov    eax,DWORD PTR [rbp-0x8]
    cdqe
    movzx  eax,BYTE PTR [rbp+rax*1-0x40]
    add    eax,0x13
    mov    BYTE PTR [rbp-0x1],al
    cmp    BYTE PTR [rbp-0x1],0x5a
    jle    0x120d <caesar+132>
    movzx  eax,BYTE PTR [rbp-0x1]
    sub    eax,0x1a
    mov    BYTE PTR [rbp-0x1],al
    mov    eax,DWORD PTR [rbp-0x8]
    cdqe
    movzx  edx,BYTE PTR [rbp-0x1]
    mov    BYTE PTR [rbp+rax*1-0x40],dl
    add    DWORD PTR [rbp-0x8],0x1
    mov    eax,DWORD PTR [rbp-0x8]
    cmp    eax,DWORD PTR [rbp-0xc]
    jl     0x11ed <caesar+100>
    lea    rax,[rbp-0x40]
    mov    rdi,rax
 #   call   0x1070 <puts@plt>
    nop
    leave
    ret

created 4 years 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