Определить, имеет ли файл ASCII-формат

function isAscii(NomeFile: string): Boolean;
 const
 SETT = 2048;
 var
 i: Integer;
 F: file;
 a: Boolean;
 TotSize, IncSize, ReadSize: Integer;
 c: array[0..Sett] of Byte;
 begin
 if FileExists(NomeFile) then
 begin
 {$I-}
 AssignFile(F, NomeFile);
 Reset(F, 1);
 TotSize := FileSize(F);
 IncSize := 0;
 a := True;
 while (IncSize < TotSize) and (a = True) do
 begin
 ReadSize := SETT;
 if IncSize + ReadSize > TotSize then ReadSize := TotSize - IncSize;
 IncSize := IncSize + ReadSize;
 BlockRead(F, c, ReadSize);
 // Iterate 
 for i := 0 to ReadSize - 1 do
 if (c[i] < 32) and (not (c[i] in [9, 10, 13, 26])) then a := False;
 end; { while }
 CloseFile(F);
 {$I+}
 if IOResult <> 0 then Result := False
 else
 Result := a;
 end;
 end;


 procedure TForm1.Button1Click(Sender: TObject);
 begin
 if OpenDialog1.Execute then
 if isAscii(OpenDialog1.FileName) then
 ShowMessage('ASCII File');
 end;