eregi('^[a-z0-9]$', $char)  
eregi('^[a-z]$', $char)

eregi('^[a-z0-9]$', $char)
eregi('^[a-z]$', $char)

function SetFullscreenMode:Boolean;
var
DeviceMode : TDevMode;
begin
with DeviceMode do
begin
dmSize:=SizeOf(DeviceMode);
dmBitsPerPel:=16;
dmPelsWidth:=320;
dmPelsHeight:=240;
dmFields:=DM_BITSPERPEL or DM_PELSWIDTH or DM_PELSHEIGHT;
result:=False;
if ChangeDisplaySettings(DeviceMode,CDS_TEST or CDS_FULLSCREEN) <> DISP_CHANGE_SUCCESSFUL
then Exit;
Result:=ChangeDisplaySettings(DeviceMode,CDS_FULLSCREEN) = DISP_CHANGE_SUCCESSFUL;
end;
end;