North Star MDS-A-D
The North Star MDS-A-D (Micro-Disk System) was a 5 1/4" disk drive for S-100 bus computers (such as the North Star Horizon, but the drive could also be used with computers from other manufacturers) in the late 1970s. It was used with the proprietary North Star DOS (with the North Star DOS file system) as well as with CP/M (with the CP/M file system).
The standard disk format used by North Star DOS had 35 tracks with 10 sectors and 256 bytes per sector. Tracks were numbered from 0 to 34, and sectors were numbered across the entire disk as blocks 0 to 349.