Here is a very simple little utility.
If you want to recycle a previously-used diskette, you can either
delete all the files and folders on it (slow) or reformat it (also
slow).  Or you can use this program, BLANK.TOS.  It zeros out the
FATs (excluding the first 3 bytes) and the root directory.  The
disk then looks just like a freshly formatted one to TOS.
You specify the drive letter, and BLANK will handle TOS or MS-DOS
disks of all sizes and formats.

The source (Laser C) follows.  It should compile with any ST C
compiler, just make sure 'WORD' is defined to 'int' or 'short', whatever
is 16 bits long.

- Moshe Braner