The ProSystem Emulator is an Atari 7800 emulator for the PC and Windows OS. The emulator was written in C++ using the Windows API and DirectX. It emulates the Atari 7800 NTSC and PAL TV standards. The emulator was originally written by Greg Stanton and then updated by others.
See the project web site for more details: http://gstanton.github.io/ProSystem1_3/