Question Missing drive space

[Eric Stork]

I have always noticed when checking Properties of my hard drive a portion of both Free and Used Space is missing but it was never big.

Recently though I saw my Free Space appears to be missing about 50GB.
Used Space is missing about 20.

What causes this?
For clarity I have attached an image showing on the Free and Used lines numbers with a difference between them.

 

[USAFRet]

298 + 631 = 929.
Given rounding errors, that is close enough to 931 as t be correct.

With a 1Tb drive, Windows reports it as 931GB. It has always been thus.

I see nothing missing.

 

[Moonstick2]

To explain further, kilo- for example as a prefix means x10^3, e.g.

1 km = 1000 m

Computer memory has always given in powers of 2. A chip that stores 2^10 bytes stores 1024 bytes. This was close enough to 1000 that it was called a kilobyte (kB) and nobody thought it would do any harm.

When people stored files on non-chip media such as tape or a disk, they weren't limited to powers of 2, and they used the more accurate 1 kB = 1000 bytes, even though it was different to the 1 kB the computer saw. People didn't fret about the 24 bytes. What was a small string's worth of data between friends?

As capacities grew, both sides still stuck to their usage. 2^20 is a megabyte to a computer, 1,048,576 bytes. About a 49 kB difference to the MB on a hard disk, but it still didn't seem a big deal.

Then disks reached gigabyte sizes. 1 GB = 1^30 = 1073741824 bytes, which is 73741824 bytes different to the 1 GB on a disk, or about 73 MB. Consumers began to notice and started to complain, but it was all too ingrained to change by then. They tried to undo the original fudge by introducing kibi- mibi- gibi- but it never really caught on.

So now you buy a 1 TB disk, which to the manufacturer is 10^12 bytes, same as 1 TW would be 10^12 watts, but to your computer those bytes are 931 GB and you're left wondering how you seem to have lost a small drive's worth of space into nothing.