Isn't this a FAQ question yet?
The Hard Drive makers have always done thier measurement that way,
because "back in the day" they could not gaurantee that every OS
being used would map the drive in the same way. It makes more
sense for them to give the raw measurement of capacity in base10,
because it was the most common starting point for conversion
to 8-bit, 9-bit, and 10-bit addressing schemes.
At this point they probably could market the drive capacity based
on its formatted capacity, but:
1) That would break backwards compatibility with the previous method.
(You might not mind, but the rest of the industry would have a fit...)
2) That would mean the capacity is marketed based on a specific OS;
which means the measurements would change every few years as a new OS
with a newer filesystem (FAT12 -> FAT16 -> FAT32 -> HPFS -> NTFS -> NTFS_SQL)
comes down the pike. (And that is not counting MacOS, Linux, BeOS, or the
various other Operating Systems/ File Systems that are still usable even on
todays drives.) At any point, some filesystem can come along which is much
better, but completely changes how the formatted drive capacity comes out in
the end. (Do you want MS telling you how much raw capacity your drive has?)
3) Most people seem to overlook that part of the capacity with any file
system has overhead taken up with the File Allocation Table, Master File
Table, inode database, or however else the OS keeps track of where data is on
the drive. And the more advanced the features are in the filesystem, the
more space will get taken for journalling, compression, encryption, and other
forms of meta-data.
(unless you are accessing the drive as a raw disk and keeping the file table
on some other media).
another scenario:
dealer: "our new car has a 20 cubic liter engine"
buyer (thinking: if I get 10 horsepower per liter on regular gas,
that comes out to 200 horsepower): "excellent, i'll take it."
dealer: "great!"
3 weeks later
"RING RING!"
dealer: "hello?"
buyer: "yes, i bought a car and i thought i had 200 hp and i only am getting 180"
dealer: "did you factor in the air-fuel mix in your power calculation?"
buyer: "No, but couldn't you have told me what that was?"
dealer: "Only if you buy the same gas from the same station all the time,
and never change elevation more than 500 ft in your travels."
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