section .text
global _start
_start:
mov eax, 8
mov ebx, file_name
mov ecx, 0777
int 0x80
mov [fd_out], eax
mov edx, len
mov ecx, msg
mov ebx, [fd_out]
mov eax, 4
int 0x80
mov eax, 6
mov ebx, [fd_out]
mov eax, 4
mov ebx, 1
mov ecx, msg_done
mov edx, len_done
int 0x80
mov eax, 5
mov ebx, file_name
mov ecx, 0
mov edx, 0777
int 0x80
mov [fd_in], eax
mov eax, 3
mov ebx, [fd_in]
mov ecx, info
mov edx, 26
int 0x80
mov eax, 6
mov ebx, [fd_in]
int 0x80
mov eax, 4
mov ebx, 1
mov ecx, info
mov edx, 26
int 0x80
mov eax, 1
int 0x80
section .data
file_name db 'myfile.txt'
msg db 'Welcome to Tutorials Point'
len equ $ - msg
msg_done db 'Written to file', 0xA
len_done equ $ - msg_done
section .bss
fd_out resb 1
fd_in resb 1
info resb 26
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.
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.
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.
There are various define directives to allocate space for variables for both initialized and uninitialized data.
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 |
| 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 can be defined using
CONSTANT_NAME EQU regular-exp or value
%assign constant_name value
%define constant_name value
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.
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