Which hole is used to mark the location of the first sector in a soft-sectored disk.

A small hole punched into a hard sectored floppy disk that serves to mark the start of the sectors on each track. Hard sectoring in a magnetic or optical data storage device is a form of sectoring which uses a physical mark or hole in the recording medium to reference sector locations. Soft sectored a floppy disk with a single index hole is known as a soft-sectored disk.