bsnes/docs/concepts/game-folders.md

A game folder is higan's way of grouping all the information and resources required to properly emulate a particular game. For example, to represent a Super Famicom game named dkc3, higan would create a game folder named dkc3.sfc, and inside it store the game data as program.rom and the save data as save.ram:

+- Super Famicom
   |
   +- dkc3.sfc
      |
      +- program.rom
      |
      +- save.ram

In contrast, other emulators typically group resources related to a game by requiring that every file has the same base name but different file extensions. For example, if another emulator loaded the game dkc3.sfc it might store the save data in dkc3.srm:

+- Super Famicom
   |
   +- dkc3.sfc
   |
   +- dkc3.srm

Why game folders?

A file extension doesn't offer much room for description, so the traditional name-based-grouping system only really works when games use a small number of files, Also, since file extensions traditionally describe the format of the file in question, it also means a game can't use two or more files in the same format.

Compared to other emulators, higan can use a larger number of files per game. For example, higan's low-level emulation of Super Famicom co-processors often requires separate firmware files. higan's MSU-1 feature supports up to 99 audio tracks per game, and higan supports up to 133 save-states per game. Thus, higan suffers from the limitations of name-based-grouping more than most.

higan's game folders allow a game to have unique, descriptive filenames for all its resources, and for each file to use the extension that's most appropriate. They also allow emulator-specific extras like save-states and the cheat database to be kept separate from the game's actual data, by putting it in a sub-folder.

For a more detailed motivation for game folders, see Game Paks on the higan website.

What's in a game folder?

A game folder collects all the information relevant to emulating a particular game. Not all of the following files are relevant for every console, or even for every game on a console, but they may be present under particular circumstances.

All the files directly in the game folder are expected to be useful to all emulators that support them:

• manifest.bml: The manifest for this game folder.
• program.rom: For most consoles, this contains the executable instructions and graphics data from the cartridge's ROM chips. For the Famicom, this contains only the executable instructions.
• character.rom: For the Famicom, this contains only the graphics data from the cartridge's ROM chips.
• ines.rom: While other consoles typically include enough hints in program.rom for icarus to guess a working manifest, the Famicom does not. Famicom games not stored in game folders typically include an "iNES header" to store that information, which icarus preserves after import as ines.rom.
• save.ram: Games that include a save feature will create this file. Note that it is only written to disk when higan exits gracefully; if higan crashes or is forced to quit, in-game saves may be lost. Other emulators sometimes call this an "SRAM file", even though the same filename is used with games that included EEPROM or Flash storage, not just battery-backed Static RAM.
• rtc.ram: Games that include a calendar or real-time clock will create this file.
• *.data.rom, *.program.rom: Files named like this are usually co-processor firmware.
• msu1.rom: Holds streamable data for the MSU-1.
• track-*.pcm: Holds streamable audio for the MSU-1.

Files that are only useful to higan specifically are placed in a higan sub-folder:

• cheats.bml: All information present in the Cheat Editor is stored here.
• states/quick/slot-*.bst: All Quick States are stored here.
• states/managed/slot-*.bst: All Manager States are stored here.