4 days back i have bought a new MY Passport Essential of 320GB, it is showing a memory of only 287 GB and 700 MB of smartware software. what about the remaining 32GB memory.
Here is some info that might help you understand how they come up with 320GB.
If you could go back and right click on it to check the drive properties.
Look at the big number right after Capacity,
You will see something like this 320,xxx,xxxx,xxx bytes followed by 287GB
That is how 320 trillion bytes = 320GB
Hard disk manufacturers report HD capacities in multiples of 1000 (i.e. 10³ or 10^3 or 10x10x10), and so 1GB = 1000MB, 1MB = 1000kB, 1kB=1000bytes. Therefore, 320GB would translate to 320,000,000,000bytes.
However, the rest of the computer industry (including the OS you are using) uses 1024 (or, 2^10 or 2 to the power 10) as the multiple. Hence, to them, 1GB = 1024MB, 1MB = 1024kB, 1kB = 1024bytes.
Therefore, the 320GB HDD or USB specified by any HD or USB manufacturer would actually translate to
320 x 10³ x 10³ x 10³ ÷ (1024 x 1024 x 1024), or roughly 298GB on your OS.
This 298GB is the actual unformatted disk capacity. As your HDD or USB is formatted, this formatting would take up some space too (depending on the type of format, the number of partitions you have, etc.). Considering this formatting space, and the small 700MB of smartware software, your “blank usable capacity” of the disk would be approximately what you are currently seeing.
Incidentally, the higher your drive size, the more ‘space’ or ‘capacity’ you stand to lose due to this difference in reporting disk capacities between manufacturers and users. You may also check out the following Wikipedia articles if you aare interested:
http://en.wikipedia.org/wiki/Hard_disk_drive#Capacity_measurements
http://en.wikipedia.org/wiki/Binary_prefix#Deviation_between_binary_and_decimal_prefixes
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