section .data
result db 0 ; переменная для хранения результата
operand1 db 0 ; первый операнд
operand2 db 0 ; второй операнд
operator db 0 ; оператор (+, -, *, /)
section .text
global _start
_start:
; ввод первого операнда
mov eax, 3 ; sys_read system call
mov ebx, 0 ; file descriptor 0 (стандартный ввод)
mov ecx, operand1 ; буфер для ввода
mov edx, 2 ; количество байт для чтения
int 0x80 ; вызов системного прерывания
; конвертация в число
mov eax, operand1
sub eax, '0'
mov operand1, al
; ввод оператора
mov eax, 3
mov ebx, 0
mov ecx, operator
mov edx, 1
int 0x80
; ввод второго операнда
mov eax, 3
mov ebx, 0
mov ecx, operand2
mov edx, 2
int 0x80
; конвертация в число
mov eax, operand2
sub eax, '0'
mov operand2, al
; выполнение операции
mov al, operator
cmp al, '+' ; сложение
je add_oper
cmp al, '-' ; вычитание
je sub_oper
cmp al, '*' ; умножение
je mul_oper
cmp al, '/' ; деление
je div_oper
add_oper:
mov al, operand1
add al, operand2
mov result, al
jmp print_result
sub_oper:
mov al, operand1
sub al, operand2
mov result, al
jmp print_result
mul_oper:
mov al, operand1
imul al, operand2
mov result, al
jmp print_result
div_oper:
mov al, operand1
mov bl, operand2
cmp bl, 0
je division_by_zero
xor ah, ah
idiv bl
mov result, al
jmp print_result
division_by_zero:
mov eax, 4 ; sys_write system call
mov ebx, 1 ; file descriptor 1 (стандартный вывод)
mov ecx, division_error ; сообщение об ошибке деления на ноль
mov edx, division_error_len
int 0x80
jmp exit_program
print_result:
; вывод результата
mov eax, 4 ; sys_write system call
mov ebx, 1 ; file descriptor 1 (стандартный вывод)
mov ecx, result
mov edx, 1
add ecx, '0'
int 0x80
exit_program:
mov eax, 1 ; sys_exit system call
xor ebx, ebx ; код возврата 0
int 0x80
ret
section .data
division_error db 'Error: Division by zero', 0
division_error_len equ $ - division_error 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