How many gigabytes does your hard drive or SSD hold? Are you sure about that?
We've already discussed how over-provisioning and file system overhead often mean that the usable
capacity of your drives is less than what's advertised, and you can check out this video
to learn more. But it turns out there's another way that you can be easily fooled,
the fact that the term Gigabyte itself can be ambiguous.
Many of us think of a Gigabyte as exactly 1 billion bytes,
however, it's a commonly accepted practice in the industry to instead use Gigabyte to mean
this many bytes. If you look closely, that's a difference of about 74 megabytes,
which is not an insignificant gap. So why does the industry have to make things so complicated?
To get the answers, we have to look way back to the early days of modern computing.
As early as the 1960s, binary addressing was already the standard for a working memory or RAM.
You see, when a computer puts something into memory, that data is assigned to a particular
address so the system can recall where it's stored. Binary addressing means that each
memory address is expressed in binary digits, that is ones and zeros. So for example, if you have a
10-bit address, there are two to the 10th power or 1024 possible addresses, not exactly 1000.
It therefore became convenient to refer to 1024 bits as a kilo bit, or the same number of bytes
as a kilo byte, even though those uses didn't strictly line up with the meaning of the kilo
prefix as it's used in fields outside of computer science. We've also seen this at times with mass
storage devices. During the 1980s, when the IBM PC platform was becoming popular, the industry
needed to decide on a standard sector size. And if you didn't know, a sector is the smallest
amount of data that can be stored at one time on a drive. The powers that be settled on making 512
bytes the default size for one sector. And if you put two sectors together, you have 1024 bytes,
which matched the binary addressing definition of kilo byte we discussed earlier.
Even today, when we're using much larger drive sizes, sectors are still defined by sizes and
powers of two, with the sector today usually coming in at 4096 bytes. However, the storage
industry today typically uses the more common exactly one billion bytes definition of Gigabyte,
since this definition allows drive makers to put larger capacities on their packaging and claim
slightly faster speeds on their spec sheets. But wouldn't it be nice to know exactly what you're
getting when you go out and buy a drive or memory card? Thankfully, more precise terms were published
in 1999 with words like megabyte and gibby byte that unambiguously refer to units that are powers
of two with the by or bi in the middle standing for binary. If you want to write that out as
abbreviation, sticking a lowercase i between the capital G and the capital B is the correct way to
do it. However, this obviously hasn't solved the problem completely. The more common words like
megabyte and Gigabyte can refer to data units in either system, and the words with by or b in
the middle haven't gained a whole lot of traction outside of tech circles. In fact, there have even
been lawsuits over how these terms are used, with customers claiming that they got less storage than
they paid for in certain circumstances. And as storage continues to grow and grow, this could
become a more significant issue. For example, there's about a 125 terabyte difference between
a petabyte and a pebby byte, but maybe we'll just constantly be storing such large files on
our devices that these differences won't matter very much. Personally, I'm looking forward to
sharing food photos on Instagram in 16k with encoded smell data. So thanks for watching guys,
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