Why is “C” the default drive letter assigned to your computer hard disk instead of A or B?

Why is the default drive in MS-Windows computers the C drive? The drives beyond that one are labelled D, E, and so on. If you plug in USB drives, they get F and G. So yeah, what about A and B?

Early PCs didn’t usually come with internal mass-storage devices due to the expense. Instead, they generally had “floppy” disk reader which used to read 5 1/4″ floppy disks, initially labeled as “A” in MS-DOS and certain other operating systems. Some systems came with two such floppy disk drives necessitating the need for a “B”.

When hard disk drives became standard in most PCs in the later 1980s, since the first two letters were already commonly used for these floppy drives, they logically labeled the third storage device “C”. Times changed and eventually, floppy disk drives were entirely removed from computers, but somehow the label ‘C’ stuck with hard disk drives. In fact, most Windows computers come with the first partition labelled as ‘Local Disk C:’ for that same reason.