Oh bless you and your youngsterness. A and B, by convention, were reserved for floppy drives and C was typically the first hard drive.
On systems with a single floppy, drives A: and B: were two logical drives mapped to the same physical drive. This enabled you to (tediously) copy files from one diskette to another.
Hard drives were a luxury.
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On systems with a single floppy, drives A: and B: were two logical drives mapped to the same physical drive. This enabled you to (tediously) copy files from one diskette to another.