 section .data
  msg db "Input a string/integer to get started:",10 ; Our message plus a linefeed character.
  msgLen equ $-msg ; Set msgLen to equal the length of our msg variable.

section .bss
  buffer resb 65 ; More extensive character amount
  input_size resq 1 ; Store number of bytes to read

section .text
  global _start

_start:
  ; Basic message printing...
  mov rax,1 ; sys_write call.
  mov rdi,1 ; 1 - Standard output.
  mov rsi,msg ; Put text offset in register ecx.
  mov rdx,msgLen ; Get value of msgLen since it's a constant.
  syscall
  
  ; Now, receive user input! Then quit...
  call _IntPut
  call _writePut
  call _exit

_IntPut:
  push rbp ; Save all registers
  mov rbp, rsp
  push rbx
  
  mov rax,0 ; sys_read
  mov rdi,0 ; Standard input
  mov rsi, buffer ; Memory location to store the input
  mov rdx, 64 ; Read the 64-bit string
  syscall
  
  mov [input_size], rax ; Save actual length of the input
  
  pop rbx ; Restore all registers
  pop rbp
  ret

_writePut:
  push rbp ; Save all registers
  mov rbp, rsp
  push rbx
  
  mov rax,1 ; sys_write
  mov rdi,1 ; Standard output (STDOUT)
  
  mov rsi,buffer ; Memory location of integer
  mov rdx,[input_size] ; Use the returned length by sys_read
  syscall
  
  pop rbx ; Restore all registers
  pop rbp
  ret

_exit:
  ; Alrighty, now onto the last bit!
  mov rax,60 ; Exit.
  mov rdi,0 ; Successful leave with no errors (Error code 0).
  syscall

created 1 month 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