Operating system for Nintendo's Wii home video game console
The Wii system software is a discontinued set of updatable firmware versions and a software frontend on the Wii home video game console. Updates, which could be downloaded over the Internet or read from a game disc, allowed Nintendo to add additional features and software, as well as to patch security vulnerabilities used by users to load homebrew software. When a new update became available, Nintendo sent a message to the Wii Message Board of Internet-connected systems notifying them of the available update.
https://en.wikipedia.org/wiki/Wii_system_software