Why is the actual capacity of hard disk drives less than the advertised capacity?

I just bought what I thought was a 400GB hard drive, but after all the procedures of installation, partitioning and formatting it turns out that I only have about 370 giga bytes available!!!! Is this sort of thing normal?? (I made sure I don't have any unallocated space left) Even if it is, I am not happy... show more I just bought what I thought was a 400GB hard drive, but after all the procedures of installation, partitioning and formatting it turns out that I only have about 370 giga bytes available!!!!
Is this sort of thing normal?? (I made sure I don't have any unallocated space left)
Even if it is, I am not happy that they use misleading numbers when advertising HDDs!
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