Sets a value in persistent cartridge data.
- The index of the value.
- The new value to set.
A cartridge can store 64 numbers (256 bytes) of data to persistent storage. This data is available the next time the user runs the cart, and persists in the player even if the cartridge is replaced with a new version of the same cartridge.
dget() function retrieves the value for the given index (0 to 63).
See cartdata() for an example.