Assembly: video mode troubles

Question

in assembly i made a script that write a string without problems, but when i go into graphic mode with

mov ah, 00h
mov al, 13h
int 10h,

all the things on the screen disappears, how can i fix that?

in graphic mode i tryied to draw a rectangle, the compiler says no error but the rect doesn't appear, how can i draw something? i tryied some examples but they doesn't work and i didn't find any guide

what is the original video mode?
i tryied to search on google and wikipedia but i cannot found anything

Answer 1

I did some research. All points to 12h but the maximum you can set the palette to is 256 colours, which may still disagree with your display. You should maybe speak to your professor on this.

Answer 2

What hardware are you using? Your graphics adaptor probably doesn't support a resolution of 320x[240 | 200] you are trying to force upon it. When a mode is not compatible, the screen generally goes black.

Answer 3

sorry i didnt explaine well, i use assembly for making OS, but i'm working with it only since march so i'm a beginner