freepascal.compiler/docs/go32ex/buffer.pp

uses
	go32;

procedure dosalloc(var selector : word;
	var segment : word; size : longint);
var
	res : longint;
begin
	res := global_dos_alloc(size);
	selector := word(res);
	segment := word(res shr 16);
end;

procedure dosfree(selector : word);
begin
	global_dos_free(selector);
end;

type
	VBEInfoBuf = packed record
		Signature : array[0..3] of char;
		Version : Word;
		reserved : array[0..505] of byte;
	end;

var
	selector,
	segment : Word;

	r : trealregs;
	infobuf : VBEInfoBuf;

begin
	fillchar(r, sizeof(r), 0);
	fillchar(infobuf, sizeof(VBEInfoBuf), 0);
	dosalloc(selector, segment, sizeof(VBEInfoBuf));
	if (int31error<>0) then begin
		Writeln('Error while allocating real mode memory, halting');
		halt;
	end;
	infobuf.Signature := 'VBE2';
	dosmemput(segment, 0, infobuf, sizeof(infobuf));
	r.ax := $4f00; r.es := segment;
	realintr($10, r);
	dosmemget(segment, 0, infobuf, sizeof(infobuf));
	dosfree(selector);
	if (r.ax <> $4f) then begin
		Writeln('VBE BIOS extension not available, function call ',
			'failed');
		halt;
	end;
	if (infobuf.signature[0] = 'V') and
		(infobuf.signature[1] = 'E') and
		(infobuf.signature[2] = 'S') and
		(infobuf.signature[3] = 'A') then begin
		Writeln('VBE version ', hi(infobuf.version), '.',
			lo(infobuf.version), ' detected');
	end;
end.