freepascal.compiler/docs/go32ex/vgasel.pas

{This example demonstrates the use of the segment_to_descriptor()
function.

It switches to VGA mode 13h (320x200x256 color), creates a selector
to the memory (based at $A000:0000), clears this memory with color
15 (white) and waits until the enter key is pressed }

uses go32;

var
	vgasel : Word;
	r : trealregs;

begin
	{ set VGA mode 13h }
	r.eax := $13; realintr($10, r);
	{ allocate descriptor to VGA memory quickly; it could be done
	with allocate_ldt_descriptors() too, but we would have to 
	initialize it by ourselves... unlike segment_to_descriptor() 
	which automatically sets the limit and the base address 
	correctly }
	vgasel := segment_to_descriptor($A000);
	{ simply fill the screen memory with color 15 }
	seg_fillchar(vgasel, 0, 64000, #15);
	{ wait for a return press }
	readln;
	{ back to text mode }
	r.eax := $3; realintr($10, r);
	{ don't deallocate vgasel, that can't be done }
end.