i wrote a simple hello world program in NASM and when i compiled it and tried to run it it said "permision denied". im running linux and the code follows:

section .data ;declare data here

msg db "Hello, World!!!", 0xa ;declare msg as the string 'hello, world!'
len equ $ - msg ;declare len as the length of msg

section .text ;declare code here

global _start ;declare where to start

_start:
;sys_write msg to stdout and stop writing at len
mov edx, len; length
mov ecx, msg; string
mov ebx, 1; stdout
mov eax, 4; sys_write
int 0x80; interupt 80h

mov ebx, 0;
mov eax, 1;
int 0x80; exit

when i compiled it i typed in
nasm helloworld.asm -o helloworld

what could be wrong???