In the 1980s, Norton produced a popular tool to Undeletion from DOS disks, which was followed by several other tools which were collectively known as the Norton Utilities.

It was possible for software developers to create a DOS 3.2 disk which would also boot on a system with DOS 3.3 firmware.

DOS 3.3 was, however, not backwards compatible; it could not read or write DOS 3.2 disks.

To avoid this, the sectors on a DOS disk were arranged on the disk in this order:

I restarted the computer with a DOS 6.0 floppy disk in drive A; DOS said it could go no further.

Spinrite, a product of the Gibson Research Corporation, lets you give a new low-level formatting to a DOS hard disk without losing the information on it.

This utility is written for DOS and you will require a DOS bootable disk with this utility on it to use it.

It covers material from the elementary ("Once the DOS disk is in the boot drive, you can turn the system on.")

This allowed the use of Enhanced Density disks, and there was a utility to read DOS 3 disks.

Was not compatible with DOS 2.0, but could read DOS 2.0 disks.