Drives are file-blind. To them, a file is just an item, and a folder is just another kind of file.
Al Fasoldt's reviews and commentaries, continuously available online since 1983
T e c h n o f i l e
Beware! An old limit can hobble your thumb drive
June 15, 2008
By Al Fasoldt
Copyright © 2008, Al Fasoldt
Copyright © 2008, The Post-Standard
A reader asked for help with an unusual difficulty. His thumb drive -- the kind you plug into a USB
port on your computer -- refused to cooperate when he copied files into it. The drive filled up even though it was mostly
To us non-computers, this seems to make no sense. To a computer, however, it was perfectly logical. A
little detective work set things right.
The thumb drive used an old filing method that goes back, in one form or another, to the earliest days
of personal computers.
To tell you about this old method, I'd like to talk about trees. (Yes, trees and drives are related.
Stick around and find out.)
Trees start out with one root and one trunk. Every branch that grows on that tree can be traced back to
the trunk, or to another branch that can be traced to the branch that was traced to the trunk. Or to another branch that --
well, you get what I mean.
And the trunk, of course, grows out of the root. One root, one trunk, but quite a few branches growing
off the trunk. And a lot of branches growing off the branches that grow off the trunk.
You don't have to be a tree surgeon to know there's a physical limit to the branches that will fit
directly on a trunk. A good guess might a dozen on a big tree, fewer on a small tree. All the other branches end up being the
End of tree discussion -- or maybe not. Because those old drives worked the same way. There was a root
-- the bottom of the storage space -- and a trunk, more or less, that held branches. Just as real trees have a limit on main
branches, old drives did, too. Their limit, forced on them by the "width" of chunks of data stored in the computer, was 256.
It was a hard limit. Item No. 256 got through the gate but item 257 couldn't get in. Nobody else with
high numbers got in, either.
If you've been paying careful attention, you've noticed that I've talked about "items" and not files.
That's because drives are file-blind. To them, a file is just an item, and a folder is just another kind of file.
A folder is just another kind of file? This tidbit gave a savvy user back in the early years of
computing a clever way around the limit of 256 items in a drive's main directory. To put more files on the drive in those
days -- think 1983 -- you took advantage of file-blindness and made sure some of the items in the main directory were folders
and not just files.
Like main branches on a tree trunk, these folders could spawn more of their own kind. There could be
folders inside folders, and other folders inside those other folders. And they could all be contained in a relatively small
number of main items.
Back to my reader's problem. To make things easier -- and to make sure anyone with a old computer
wouldn't be left out -- the company that made his thumb drive formatted it the old way, using that old file system. And when
this reader tried to dump a few thousand files into the main directory -- into the root of the drive -- every item from No.
257 on up ran into that wall. They didn't get copied.
So my advice was simple: Make a single folder in that main directory -- the name doesn't matter -- and
then copy all the files and folders into that one main folder. That would use up only one of the 256 "slots" in the root
That solved the problem, and the thumb drive was then able to hold all the files that were copied to
it. And I was reminded that sometimes the answers to our modern-day technical problems are, indeed, rooted in the past.