You know you're getting old when you are shocked that someone asks what A: and B: are for, having never seen nor conceptualized that they were once floppy drive letters.
Seriously! I remember buying my first box of ten 3.5" floppies, which stored 1.44MB of data EACH, after years of using the older 360KB 5.25" disks, and marveling how much storage I was carrying in that little box... Kids today, with their USB sticks and DVD drives and Internets. Grumble grumble. Get off my lawn!
There's the 720kb 3.5" floppies too. I remember there was a shady outfit(s) that sold punchers you could use on these disks to trick the drive into thinking it was a 1.44mb disk.
Of course, those 720kb disks were never intended to store 1.44mb of data, so while you could write that data to the disk, and maybe even read it immediately after, the odds that you could read it again awhile later were pretty low.