dos assembly can't write file

Question

I wrote a 16 bit .com file which create a file

but it don't create any file.

I tried on windows 7 32 bit. and inside dosbox.

the source code is here

how can I write to a file?

org 100h

        call open_new_file
        mov ah, 40h;write
        mov bx, [new_file_handle]
        mov cx,2;write 2 bytes
        mov dx, temp
        int 21h

        mov ah, 3eh;close file
        mov bx, [new_file_handle]
        int 21h

        mov ah, 00
        int 16h;wait key

        mov ax, 4c00h
        int 21h;exit

open_new_file:
        push bp
        mov bp, sp
        mov ah, 3dh;open file
        mov al, 02h;write only
        mov dx, new_file_name ;out.kty
        int 21h
        mov [new_file_handle], ax
        leave
        ret


temp:
        dw 0xffaa

new_file_handle:
        dw 0
new_file_name:
        db "out.bin", 0

thanks!

Answer 1

It looks like int 21, 3D is "open file". Did you mean int 21, 3C which is "create or truncate?"

If you checked the return value, you'd probably see CF=1 indicating an error. I'm guessing AX would be... 2?