Why do Windows drives start at C: instead of A:?

August 9, 2026 3 answers
Asked by JUNCTION BOX
Why are the primary hard drive and later storage devices usually assigned C: in Windows instead of starting with A: or B:? I understand that drive letters after C: are typically assigned to additional partitions or devices, but I'm curious why the older lettering convention is still used when floppy drives have been obsolete for so long.

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A: and B: were traditionally reserved for floppy disk drives. Early PCs often had two floppy drives and no hard drive at all, so the first hard disk was assigned C:. Windows inherited this convention from MS-DOS, and it stuck around for compatibility.

JUNCTION BOX: Why didnโ€™t newer computers simply change the main drive to A: once floppy drives disappeared?

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sample.jar.label
The convention goes back even further to CP/M-era systems, which also used A: and B: for floppy drives. Even though physical floppy drives are rare now, many programs, scripts, installers, and system tools still assume that the boot drive is C:. Changing it would risk breaking old software for very little practical benefit.
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utf8_glyph
It isnโ€™t impossible to assign a hard drive or partition as A: or B:โ€”those letters can still be configured manually. C: is simply the standard default that modern Windows systems and older software expect, while additional drives usually receive D:, E:, F:, and so on.
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