 sectiosn .data
    prompt db 'Enter the number of seconds for the alawrm:', 0
    alarm_msg db 'Time is up!', 0
section .text
    global _start
_start:
    ; prompt the user for the number of seconds
    mov eax, 4 ; system call for "write"
    mov ebx, 1 ; file descriptor for stdout
    mov ecx, prompt ; address of the prompt message
    mov edx, 43 ; length of the message
    int 0x80 ; make the system call
    
    mov eax, 3 ; system call for "read"
    mov ebx, 0 ; file descriptor for stdin
    mov ecx, esp ; address of the buffer to read into (the top of the stack)
    mov edx, 10 ; maximum number of characters to read
    int 0x80 ; make the system call
    
    ; convert the user input to a number
    xor ebx, ebx ; clear ebx for the loop counter
    mov bl, [esp] ; move the first character of the input into bl
    cmp bl, 0x30 ; check if the character is a digit
    jl error ; jump to the error label if it is not
    sub bl, 0x30 ; convert the character to a number
    mov eax, ebx ; save the number in eax
    
    mov bl, [esp+1] ; move the second character of the input into bl
    cmp bl, 0x30 ; check if the character is a digit
    jl validate ; jump to the validate label if it is not
    sub bl, 0x30 ; convert the character to a number
    mov ebx, 10 ; multiply eax by 10
    mul ebx ; eax = eax * ebx
    add eax, ebx ; eax = eax + ebx (ebx = second digit)
    
validate:
    cmp eax, 0 ; check if the number is positive
    jle error ; jump to the error label if it is not
    cmp eax, 3600 ; check if the number is less than 1 hour (3600 seconds)
    jg error ; jump to the error label if it is not
    
    ; wait for the specified number of seconds
    mov ebx, eax ; save the number of seconds in ebx
    mov eax, 0 ; system call for "pause"
    int 0x80 ; make the system call
    
    ; print the alarm message
    mov eax, 4 ; system call for "write"
    mov ebx, 1 ; file descriptor for stdout
    mov ecx, alarm_msg ; address of the alarm message
    mov edx, 12 ; length of the message
    int 0x80 ; make the system call
    
    ; exit with status 0
    mov eax, 1 ; system call for "exit"
    xor ebx, ebx ; return status 0
    int 0x80 ; make the system call
    
    ; print an error message and exit with status 1
    mov eax, 4 ; system call for "write"
    mov ebx, 1 ; file descriptor for stdout
    mov ecx, prompt ; address of the prompt message
    mov edx, 34 ; length of the message
    int 0x80 ; make the system call
    
    mov eax, 4 ; system call for "write"
    mov ebx, 1 ; file descriptor for stdout
    mov ecx, esp ; address of the user input buffer
    mov edx, 10 ; length of

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