function GetFileSize(filename: TFileName): String;
var
fich : file;
size : Integer;
begin
OpenFile();
AssignFile(fich, filename);
FileMode := 0;
Reset(fich, 1);
size := FileSize(fich);
CloseFile(fich);
case size of
0..1023 : result := Format('%d octets', [size]);
1024..10239 : result := Format('%.1f Ko', [size/1024]);
1048576..1073741823 : result := Format('%.1f Mo', [size/1048576]);
else
result := Format('%.1f Go', [size/1073741824]);
end;
end;