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You are watching: Why is there no a or b drive

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The C: journey is the default installation place for Windows, if you have actually a CD/DVD journey on your maker it’s likely the D: drive, and also any added drives loss in heat after that. What about the A: and B: drives?

Image through Michael Holley.

Today’s concern & price session pertains to us courtesy of SuperUser—a subdivision of stack Exchange, a community-drive grouping of Q&A web sites.

The Question

If you a geezer of a details vintage—we won’t start naming years—the answer come this question is patently apparent to you. For younger geeks, however, the A: and B: drive have always been mysteriously unaccounted because that on their computers.

SuperUser reader Linker3000 poses the question:

In home windows you have actually a C: drive. Everything labeled beyond that is through the adhering to letter.

So your 2nd drive is D:, her DVD is E: and if you put in a USB pole it becomes F: and also the adhering to drive G:. And so on and also so forth.

But then, what and also where space A: and also B:?

What and also where, indeed? thankfully we have some jar geeks come answer the query.

The Answers

Image by AJ Batac.

Veteran geezer Adam Davis offers an comprehensive look in ~ the lacking drive letters:

The early on CP/M and also IBM computer style computers had no tough drive. You had one floppy drive, and also that was it. Unless you spent an additional $1k or for this reason on a second floppy drive, then your system was smokin’! If girlfriend only had one drive it was typical to boot from one disk, placed in the various other disk through your programs and data, then operation the program. When the regimen finished, the computer would request the you reinsert the boots disk therefore you could use the command heat again. Copy data from one disk come the other was a series of “Please insert source disk right into drive A:… you re welcome insert destination disk right into drive A:… you re welcome insert source disk into drive A:…”

By the time tough drives came to be cheap, the “expensive” computers commonly had 2 floppy cd driver (one to boot and also run typical programs, one to save data and run particular programs). And also so it was typical for the motherboard hardware to support two floppy cd driver at fixed system addresses. Because it was developed into the hardware, that was believed that structure the very same requirement right into the OS to be acceptable, and any difficult drives added to the an equipment would begin with decaying C: and so forth.

During the shift from 5.25″ disks (which to be actually, physically floppy) to 3.5″ disks (which were encased in a harder plastic shell) it was typical to have both drives in one system, and again it was sustained on the motherboard v hardware, and also in the OS at fixed addresses. As very few systems ran the end of journey letters, it to be not assumed to be necessary to take into consideration making those drives reassignable in the OS until much later when drives to be abstracted along with addresses because of the plug’n’play standard.

A most software was developed since that time, and unfortunately lot of it supposed to see permanent storage ~ above the C: drive. This consists of the BIOS software application that boots the computer. You can still attach two floppy drives, boot into DOS 6.1, and also use it as you would have actually in the beforehand 90’s, v floppy drives A and B.

So largely the reason for beginning the hard drive at C is for backwards compatibility. When the OS has actually abstracted data warehouse to part degree, the still treats A and B differently, in such a way that enables them to be gotten rid of from the mechanism without changing the OS, caching lock differently, and due to at an early stage viruses dealing with their boots sector with more caution than the hard drive’s boots sector.

SuperUser contributor Nick chimes in through an exciting anecdote structure off that the third paragraph that Adam’s answer dealing with letter assignments:

Less an answer, much more of one anecdote. In this Microsoft article, the says:

“You can assign the letters C v Z come each journey on your computer. A and B are usually reserved for floppy disk drives, but if your computer system does not have actually floppy decaying drives, you deserve to assign A and B come volumes.”

So once I constructed a brand-new computer newly with two interior drives, one because that the OS and one because that data, ns thought, hey!, I’ll do my data drive “A”. Ns felt all rebellious till I uncovered that Windows will certainly not index drives lettered A or B. :(

Took me rather a if to number out what the problem was, however I discovered some other world who endured the same issue when they supplied A or B because that a drive. As soon as ns assigned the drive a various letter, windows indexed the drive. So much for being rebellious.

So lot for gift rebellious indeed—if you want to live ~ above the sheet you can assign a data journey to A: and also B:, but not a boots drive.

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Jason FitzpatrickJason Fitzpatrick is the Editor in cook of LifeSavvy, How-To Geek"s sisters site concentrated life hacks, tips, and also tricks. He has over a decade of endure in publishing and has writer thousands of short articles at testimonial Geek, How-To Geek, and Lifehacker. Jason served as Lifehacker"s Weekend Editor before he joined How-To Geek. Read full Bio »