Very Small Control System (VSCS).
Control System (or Operating System, but officially called Control System) in assembly language. It's a VERY small system; its essence is maximum minimalism. But even in it, I attempted to implement the functions of a full-fledged system, such as a bootloader, reading data from other disks and sectors, rebooting, and even error checking.
Released into the public domain under CC0 (see the "LICENSE" file for details).