The Apple IIgs Operating System, GS/OS sported advanced-for-its-time features like on-the-fly loadable and unloadable device drivers. It also had so-called "FSTs" or File System Translators, making it possible for the OS to understand new disk and partition formats without rebuilding the actual kernel. Nowadays Linux does this without blinking thanks to VFS and kernel modules, but in 1988 on a 512k 16-bit machine, it was revolutionary.