Problem with plotting pixels

[MattCarpenter]

I am making a small 'kernel' in C. I compile the c file as a binary and it loads just fine with my pmode bootloader. When i try to write color data to 0xA0000 (which ppl tell me is the video memory) my computer re-boots! whats up with that?

[carbonBased]

0xA0000 is video memory considering your current data segment descriptor has a base of 0, and a limit above 0xAFFFFF.

What's your code look like?
And are you sure pmode is setup correctly?

Jeff

[MattCarpenter]

typedef unsigned char byte;
byte *VGA = (byte *)0xA0000;
short offset;

offset = 320*10 + 10;
video[offset]=7;

[RetainSoftware]

I hope you've switched to a graphicsmode that has A0000 as a base address.
Otherwise if you've plain text then it will be B8000 and no pixels.

this code is wrong though
video[offset]=7 should be VGA[offset]=7

[MattCarpenter]

how do you switch into a graphics mode?

[anton]

The easyest way, is to switch to it while in real mode(mov ax,00xx; int 0x10, where xx is the mode:
bit 7 is set to clear the screen, others 0x12 that is 640x480 4 bit). It is a pain(you'l need to program
the graphical chip set like ega,vga or S3) to do it in pmode.