Minecraft worlds are huge; supposedly, nearly 130 quadrillion blocks. (Zoom out a little on that site and you'll see it.) Anyways, I looked in the Save folder (C:\Users\username\AppData\Roaming.minecraft\saves), and the world I'm currently playing in has a folder of the same name as my world. This folder is only 12 Mb. Does Minecraft really store 130 quadrillion blocks in 12 Mb, or is there some kind of insane level encoding going on? Even if there is crazy encoding ("Saving chunks", whatever that means) in the game itself, one does not simply fit 130 quadrillion blocks into well under one gigabyte of physical memory.
How does Minecraft store world data? As a programmer, I understand tilemaps that represent 1 or more blocks (in a 2D sense) per byte, and world data of that sort, but I can simply not wrap my mind around how 130 quadrillion blocks take up so little memory.