MicrosoftAnonymous2460 Ah youth!
Windows 3.1 was the OS version from the 1980s and early 90s. PCs originally had 16 bit intel processors, and 32-bit processors were the new ones. Compatibility for running 16-bit apps on the 32-bit processors existed, but was handled by NTVDM, a kernel component which understood the hardware level requirements. NTVDM never existed on x64 operating systems, and has been removed from the OS entirely these days. These emulator tool provide a software emulation of what the NTVDM would have done, plus emulation of the hardware instructions using the modern instruction set. This allows apps build as 16-bit executables to run, and often the emulator provides a full DOS emulation for the app to run in.
