Background
The Atari 7800 ProSystem, or simply the Atari 7800, is a home video game console officially released by Atari Corporation in 1986 as the successor to both the Atari 2600 and Atari 5200. It can run almost all Atari 2600 cartridges, making it one of the first consoles with backward compatibility. It shipped with a different model of joystick from the 2600-standard CX40 and Pole Position II as the pack-in game. Most of the announced titles at the launch were ports of 1981–83 arcade video games.
(Source : https://en.wikipedia.org/wiki/Atari_7800)
ROM Info
Atari 7800 ROMs should all be in the .a78 format to run properly on most emulators, including the one on this site.