The drive’s packaging says 1 terabyte of storage – but the computer claims there’s only 931 gigabytes. So did the computer make a mistake or are the manufacturers cheating on the storage sizes of the hard drives? Neither nor! TECHBOOK explains the memory confusion.
Anyone who has ever bought an external hard drive or a computer may have noticed that the storage space specified on the package does not always correspond to the actual space on the disk – it is often dozens of gigabytes (GB) less. In the case of a terabyte, that is approx. 931 GB, or a memory declared as having 500 GB of memory actually only has 465 gigabytes. But why is it like that? TECHBOOK explains what the crooked amounts of storage are all about.
Computers count differently than people
The reason for the difference lies in the way computers deal with numbers: we are used to counting by tens. 10, 100, 1000 – our number system is decimal. A computer works differently because its foundation is ones and zeros, on and off. Therefore, its number system is binary, i.e. based on two digits. With the different arrangement of 0 and 1, all other numbers can be represented. A 2 in binary notation becomes a 10. A 6, on the other hand, is a 110. This is due to the binary number system, in which the power of 2 is always formed. That is, the previous number is taken times 2. Put simply, the binary number system can result in a table like this:
The computer can only calculate in powers of two. In order to display our decimal numbers, the computer has to activate the power of two with a 1. All powers of two that get a 0 are excluded from the calculation. To translate the 18 into a binary code, the 16 and the 2 with the code 1 are activated. All other powers of two get the code 0. This results in the binary code 10010. A 300, on the other hand, has the binary code 100101100.
So the way we count bits and bytes doesn’t really apply to the binary system at all, because when you use the terms kilo, mega, and giga, you mean a thousand times something. Just as one kilogram equals 1000 grams. The problem: A gigabyte is not a thousand times a megabyte – a gigabyte is exactly 1024 megabytes. So 24 more than 1000. The memory of the hard drive is therefore smaller in the calculation of the computer.
Binary computation makes hard drive memory appear smaller
This excess is responsible for the fact that what is stated on the packaging and the actual gigabytes initially appear different. Because many manufacturers take the giga literally and produce hard drives with actually 500 gigabytes and thus 500,000 megabytes. But if it takes 1024 megabytes to fill a gigabyte, 500,000 MB is not enough for 500 GB, but only achieves 465 “real” gigabytes for the computer. Thus, the computer shows a smaller memory – it represents a gigabyte in a binary notation differently. However, the memory capacity is not less, but is calculated differently depending on the decimal or binary display.
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The information provided by the manufacturer is therefore not incorrect. The only problem is that it is difficult to define a unit based on a binary number system with prefixes such as mega-, giga- or peta-, because these are based on tens of the decimal system.