DOS extender
There are two updates known to have been published for Windows 3.0. One of them is Windows 3.0a, released in December 1990. It modified Windows' DOS extender—a program that enables DOS applications to access extended memory—to prevent errors caused by software calling into real-mode code when Windows is loaded in standard mode. It also simplified the installation process and alleviated crashes associated with networking, printing, and low-memory conditions.