freepascal.compiler/docs/go32ex/buffer.pp

Program buffer;

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 = 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.