A:
Physical drive located on PC or IBM compatible computers. The A: drive is a drive letter used by the 3.5-inch floppy disk drive or the 5.25-inch drive on early computers. Often the A: drive is setup in CMOS setup as the first bootable drive on IBM compatible computers, which allows you to use bootable floppy diskettes to fix and repair their computer. Today, it is becoming more rare to see an A: drive as more computers no longer ship with any floppy disk drive.
Also see: B:, C:, D:, Drive letter, Floppy definitions, Floppy drive