Mode13h

Is there a way to test if the video went to mode 13h?

I use this code to go into mode13h

Code:

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void SetGraphicsMode()
{
  _AH = 0;
  _AL = 0x13;
  geninterrupt(0x10);
}

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I want to make SetGraphicsMode() return a bool or an int so I know if I went to mode14h or not, how would I go about doing this?

You should check the RBIL under interrupt 10h to see what values are returned in what registers.


int SetVideoMode(int mode)
{
asm {
mov ax,13h
mov ah,0
int 10h
}
return _AX;
}


I'm assuming that the error code is return in _AX. Most BIOS calls use this register to return error codes to the caller. If not, just change the returned register.

There is no reason this call should fail, though.

I noticed in your code you had ax as 13h, and ah as 0. I usualy have ah as 0 and al as 13h, what is the difference?

Quote:

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Originally posted by JoshG
I noticed in your code you had ax as 13h, and ah as 0. I usualy have ah as 0 and al as 13h, what is the difference?

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AX consists of AL (low byte) and AH (high byte). When you set AX to a number < 256, it is set to the low byte, so both ways works.