OSDev.org

Hi
I have now decided to write my stuff in C and so far the Get and Set cursor actions that I wasn having trouble with in asm are now very easy. I am having a little trouble with printing a charachter to video RAM though. With this function, nothing happends:

void Print_Char(UCHAR ascii_char, UCHAR Page)
{
UINT far *video_ram = (UINT*) 0xB8000;

*video_ram = ascii_char;

}

I am writing this in real mode DOS Turbo C++ (it's a C file). At the moment, I am just wanting to write the argument ascii_char to the very top left had corner of the screen.

What am I doing wrong?

BTW I am not particually experienced with using pointers in a HLL, as in Turbo Pascal and Delphi I never used pointers (never got round to it).

Thanks
Steven Graham

hmm, if you're using turbo C, you'd better use the MK_FP macro that will construct a far pointer from a segment and an offset. casting 0xb8000 is likely to produce something like 000b : 8000 or 8000 : 000b, but certainly not b800:0000 as expected ...

Right

void Print_Char(UCHAR ascii_char, UCHAR Page)
{
UCHAR far *video_ram = 0;

video_ram = MK_FP(0xB800, 0);
*video_ram = ascii_char;
video_ram++;
*video_ram = 7;

}

With this, the top left char is printed as it should, great, but why is the rest of the screen all red??

Thanks
Steven Graham

This is odd

it works perfectly under the IDE, but not at all when run by it's self!

this includes code I have for getting and setting the screen cursor!

ahh sorry, my mistake

I'd better set up my turbo C better :-[