When I conducted my summer training for teachers, one of the most prevalent questions to me was regarding the “missing” hard disk space.

They kept asking why is it that when you check the storage capacity of a hard disk in Windows Explorer, it’s not exactly as what it is stated even if the hard disk is still new?

At the right is an image of my laptop’s hard disk space. It is supposed to be 40 GB (gigabytes) but why is it only showing 37.2 GB? (Click on the image to make it larger)

Where’s the “missing” 2.8 GB?

The answer lies in the way disk space is being reported. You see, hard disk manufacturers (humans) reports the data in decimal number system while computers in binary. In a decimal system, numbers are counted from 0-9 and expressed as powers of ten. In a binary system, there are only two numbers, 0 and 1 and expressed as powers of two. The prefix BI means two. Computers can only crunch zeros and ones.

Got it? Let’s proceed.

1 KB (kilobyte) can be understood by humans as 1,000 bytes because 10^3 (10 multiplied by itself 3 times) is 1,000 while computers can understand it as 1,024 bytes because 2^10 (2 multiplied by itself 10 times) is 1,024. There’s an immediate discrepancy of 24 bytes right there. As you go higher in value, the discrepancy also rises.

>> 1 MB (megabyte) in decimal is equal to 1,000,000 bytes (10^6) but equal to 1,048,576 bytes (2^20) in binary.

>> 1 GB (gigabyte) in decimal is equal to 1,000,000,000 bytes (10^9) but equal to 1,073,741,824 bytes (2^30) in binary.

>> and so on..

So now, we go back to my question above.

When my hard disk space shows 37.2 GB instead of 40 GB, it simply means that my hard disk has a storage capacity of only 37.2 GB. That is, 37.2 binary GB. The “missing” 2.8 GB did not go anywhere. It’s just that the disk space is being reported in two different ways.

Additional note: This is not only applicable to hard disks but also to your USB drives, MP3 players, cell phone and digital camera memory cards or any other digital storage devices.

DISCLAIMER: Kung sumakit man ang ulo nio sa pag-intindi nito, hindi ko na kasalanan un, hehe..

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Tags: GEM, hard disk