Windows 2.1x is a family of Microsoft Windows graphical user interface-based operating environments.
Less than a year after the release of Windows 2.0, Windows/286 2.10 and Windows/386 2.10 were released on May 27, 1988. These versions can take advantage of the specific features of the Intel 80286 and Intel 80386 processors.
Windows/386 was much more advanced than its predecessor. It introduced a protected mode kernel, above which the GUI and applications run as a virtual 8086 mode task. It allowed several MS-DOS programs to run in parallel in "virtual 8086" CPU mode, rather than always suspending background applications. (Windows applications could already run in parallel through cooperative multitasking.) Each DOS application could use as much low memory as is available before Windows is started, minus a few kilobytes of overhead. Windows/386 also provided EMS emulation, using the memory management features of the 80386 to make RAM beyond 640K behave like the banked memory previously only supplied by add-in cards and used by popular DOS applications. (By overwriting the WIN200.BIN file with COMMAND.COM, it is possible to use the EMS emulation in DOS without starting the Windows GUI.) There was no disk-based virtual memory, so multiple DOS programs had to fit inside the available physical memory; therefore, Microsoft suggested buying additional memory and cards if necessary.
Neither of these versions worked with DOS memory managers like CEMM or QEMM or with DOS extenders, which have their own extended memory management and run in protected mode as well. This was remedied in version 3.0, which is compatible with Virtual Control Program Interface (VCPI) in "standard mode" and with DOS Protected Mode Interface (DPMI) in "386 enhanced" mode. Windows 3.0 also had the capability of using the DWEMM Direct Write Enhanced Memory Module. This is what enables the far faster and sleek graphical user interface.