Dosbox

[DeXecipher]

I know this isn't exactly c++ but Im looking to call c/c++ functions from assembly. I got this straigt out of the nasmdoc and Im confused as to why this compiles but does not run on dosbox.

section .data
string: db 'Hello World', 0Ah
length: equ 13
global _main:
_main:
mov eax, 4
mov ebx, 1
mov ecx, string
mov edx, length
int 80h

mov eax, 1
mov ebx, 0
int 80h