Calculating Memory Size

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Understanding how to calculate memory size required for different files requires us to learn the terms used for differnt memory sizes. We could calculate all memory sizes in bits (a single 1 or 0 in binary), but for most memory this would mean showing capacity in the many millions which is difficult.

Hard drive - GCSE Computer science

Instead, we use a set of standard sizes that scale up as memory requirements get larger:

  • 1 bit = a single 1 or 0
  • 4 bits = a nibble
  • 8 bits = a Byte

After a Byte, memory is calculated in one of two ways. If we are discussing the size of files or storage devices, multiples of 1000 are used. However, if we are discussing the transfer of data, multiples of 1024 are used.

1 KiloByte = 1000 Bytes1 KibiByte = 1024 Bytes
1 MegaByte = 1000 KiloBytes1 MebiByte = 1024 KibiBytes
1 GigaByte = 1000 MegaBytes1 GibiByte = 1024 MebiBytes
1 TeraByte = 1000 GigaBytes1 TebiByte = 1024 GibiBytes

Knowing this allows us to calculate how many files of a certain size can fit into another. For example:

David has a photo that is 2MB. How many of these can he store on his 3GB memory stick?

The first step is to put both in the same capacity:

3 * 1000 = 3000

Next, we can work out how many 2MB photos fit into 3000 MB:

3000 / 2 = 1500

So the answer is 1500 2MB photos could be stored on the disk if no other space is taken by other files.

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