; This programs checks if a number n>1 is prime
; it checks for divisors from 2 to n-1, but does not terminate if n=1
section .data
    is_prime db "prime"
    is_len equ $ - is_prime
    not_prime db "not prime"
    not_len equ $ - not_prime


section .text
global _start
_start:
    mov ebx, 37 ; hardcoded number to check
    call check_prime

; n is loaded from ebx
check_prime:
    mov ecx, 2 ; number to start at for primality check
    loop:
        cmp ecx, ebx
        je end_is_prime ; if at the end of the loop, call end_is_prime

        ; operate division (bdx/ecx) <=> (num/current)
        xor edx, edx ; will store remainder
        mov eax, ebx
        div ecx

        cmp edx, 0 ; check if ecx divides ebx
        je end_is_not_prime
        inc ecx    ; continue loop
        jmp loop


; success
end_is_prime:
    mov edx, is_len
    mov ecx, is_prime
    mov ebx, 1       ; stdout
    mov eax, 4       ; sys_write
    int 0x80

    mov eax, 1        ; sys_exit
    mov ebx, 0        ; exit code 0
    int 0x80          ; syscall

; failure
end_is_not_prime:
    mov edx, not_len
    mov ecx, not_prime
    mov ebx, 1       ; stdout
    mov eax, 4       ; sys_write
    int 0x80         ; syscall

    mov ebx, 1        ; exit code 1
    mov eax, 1        ; sys_exit
    int 0x80          ; syscall