Family Computer Disk System

The Family Computer Disk System (also called the Famicom Disk System) is a peripheral for the Family Computer that was only released in Japan, on February 21, 1986. It could play specific games that were released on a proprietary, two-sided floppy disk format known as Disk Cards.

The first Metroid was originally released for the Family Computer Disk System in 1986 before receiving an overseas release for the Nintendo Entertainment System, which utilizes game cartridges like a standalone Family Computer but unlike the Family Computer Disk System. The Family Computer Disk System version of Metroid has several differences, most notably the fact that it allows users to directly save their game progress whereas the Nintendo Entertainment System version uses a password system instead.