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# Recover HDD space

Posted on 2006-05-26
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Hi. I bought an 80GB space hard disk, but after the XP installation I cannot see more than 74GB space. I heard that I must use some programs to recover the rest of space? Can anybody help me? Thanks
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Question by:quentin1

LVL 95

Accepted Solution

No, you're getting the right amount of space.  The problem is the drive is marketed as an 80 GB drive where 80 GB = 80,000,000,000 bytes. (80 billion bytes).  BUT, computers don't do math like that - computer math is by powers of 2.  So while you may think of 1 GB as 1 billion (1,000,000,000) bytes, The computer sees 1 GB as 1,073,741,824 bytes.  When you divide the 80,000,000,000 bytes the marketers are telling you you're getting by the 1 GB the computer understands, that equals 74.5 GB or so to the computer.
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LVL 8

Expert Comment

This is like the comercial GB.

1 Giga can mean 10 ^ 9 OR 2 ^ 30 so even though in computer  1 GB  actually means 1024 MB for measure of quantity of mass storage they've picked the 10 based measurement to make it sound bigger.

http://en.wikipedia.org/wiki/Giga

What is funny is that sometimes 1 giga really means one giga and sometimes it doesn't. You have to keep your eyes open fo this.
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LVL 32

Expert Comment

Isn't it amazing how marketeers change the definition of terms to suit their own purposes.   From the beginning of "computer time" the following definitions have been used:

"K" = 1024
"M" = 1024 x 1024 = 1024 K = 1,048,576
"G" = 1024 x 1024 x 1024 = 1024 M = 1,073,741,824

On the very first computers, if you bought "1 K" of RAM you got 1024 bytes.  64K got you 65,535 bytes of RAM.  Early disk drives started out the same as well.  But somewhere along the way, one of the disk vendors started rating their drives in DECIMAL MB (i.e. "M" = 1000 x 1000 = 1,000,000) rathan than BINARY MB.  Since a decimal based MB is a bit smaller than a binary MB it made that vendors drive artifically "bigger" than the others.  Soon after all the drive vendors were lying the same way.

So what  we have now is that 80 = 74, which of course, it obviously not true.  But can be made to be true by changing the definition of how these numbers are measured.  It's a lot like the equality: 1 in = 2.54 cm  Obviously 1 <> 2.54 but when you add the units in and cm the equation holds.

The confusion on HDD sizes is because the units "GB" are used interchangeably for both decimal-based "G" and binary-based "G" and therefore intentionally confuses disk buyers like yourself.
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LVL 8

Expert Comment

Jhance.. it is exactly the contrary... ONLY when talking about BYTES is that 1 Giga is 2 ^ 30. All other measures use GIGA as 10 ^ 9..

2 GHz  for example is 2,000,000,000 Hz... BUT when you deal with a Hard drive size well it is Giga Bytes with a capital B. So that's simply a missuse of the rule as I've said before. (it is like the RMS in sound.)
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Author Comment

I see now. Thanks for answers
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