MSX-DOS was a disk operating system developed by Microsoft for the MSX home computer standard. It was a combination of MS-DOS v1.25 and CP/M-80 v2.2. The goal was to add disk capabilities to MSX BASIC and provide a more affordable software medium than memory cartridges. MSX-DOS was compatible with CP/M-80, allowing users to access a wide range of software. It had a booting system that allowed for the use of a disk operating system. MSX-DOS did not have subdirectories like later versions. MSX-DOS 2 was released in 1988 and featured improvements such as subdirectories and memory management.
https://en.wikipedia.org/wiki/MSX-DOS