Samsung NP900X4C-K01US 사용자 설명서

The capacity of the storage device (HDD, SSD) of the manufacturer 

is calculated assuming that 1KB=1,000 Bytes.
However, the operating system (Windows) calculates the storage 

device capacity assuming that 1KB=1,024 Bytes, and therefore the 

capacity representation of the HDD in Windows is smaller than the 

actual capacity due to the difference in capacity calculation.  

(E.g. For a 80GB HDD, Windows represents the capacity as 74.5GB, 

80x1,000x1,000x1,000 byte/(1,024x1,024x1,024)byte = 74.505GB)
In addition, the capacity representation in Windows may be even 

smaller because some programs such as Recovery may reside in a 

hidden area of the HDD.

The memory capacity reported in Windows is less than the actual 

capacity of memory.
This is because BIOS or a video adapter uses a portion of memory 

or claims it for further use. 

(E.g. For 1GB(=1,024MB) memory installed, Windows may report 

the capacity as 1,022MB or less)