@starfrost It was from about 1983ish, I remember using it in parallel with PC-DOS 2.0. It didn't have the modern features of DOS 2.0 like hierarchical directories, but it did have a much more advanced FORMAT.COM utility that could format floppies to 42x10x2 rather than the 40x8x2 DOS 1.1 standard or the 40x9x2 DOS 2.0 standard. Marked "IBM Internal Use Only" (my mother was an IBMer so she could get it for our home PC). The developer was a guy named Jack Botner VE3LNY aka TOROLAB(BOTNER).