A complete set (often called a "full reference set") is a collection that includes every single game supported by a specific version of the . Unlike console emulators that use a single file for a game, arcade hardware is complex. A single arcade game in MAME is actually a "ROM set"—a ZIP archive containing the digital dumps of every individual chip on the original arcade motherboard.
A complete ROM set often requires additional files to run high-end games or look modern: CHDs (Compressed Hard Disk Images) mame rom complete set