Alpha worlds consist of several files, all held together in one folder under a very rigid directory structure.

Level

The level is a file called "level.dat" in the root of the world.

Chunks

Chunks are stored in folders inside the world corresponding to their coordinates in base-36.

Persistent data for players is stored in a folder called "players". Each player has a file called "<username>.dat".

There are several approaches to map generation.

Two-dimensional noise functions can be used to provide a terrain height at certain coordinates.