Printing To Screen: Difference between revisions

Keep in mind that this way of writing to video memory will _only_ work if the screen has been correctly set up for 80x25 video mode (which is mode 03). You can do this either by initializing every VGA register manually, or by calling the ''Set Video Mode'' service of the BIOS Int10h while you're still in real mode (in your bootsector, for instance). Most BIOS's do that initialization for you, but some other (mainly on laptops) do not. Check out [[Ralf Brown's Interrupt List]] for details. Note also that some modes that are reported as "both text & graphic" by mode lists are actually graphic modes with BIOS functions that plot fonts when you call char/message output through Int10h (which means you'll end up with plain graphic mode once in [[Protected Mode]]).

Another common mistake, e.g. in numerous tutorials spread across the net, is to link the .text section of your kernel/OS to the wrong memory address. If you don't have memory management in place yet, make sure you're using physical memory locations in the linker script.