I bought some blank DVDs to store backup files. The disks say that they hold 4.7Gb of data, but when I put one in my computer, Vista shows it having 4.3Gb of space. What happened to the other 0.4Gb?
The discrepancy is caused by the fact that there are 2 ways of defining computer memory. Let’s start from the beginning, technically speaking, this is how computer memory is measured:
- 1 Kilobyte is 1,024 bytes (2 to the power of 10)
- 1 Megabyte is 1,048,576 bytes (2 to the power of 20)
- 1 Gigabyte is 1,073,741,824 bytes (2 to the power of 30)
Now, as you can imagine, those number are pretty hard to remember, so most people think of 1 Kilobyte as 1,000 bytes, 1 Megabyte as 1,000,000 bytes and 1 Gigabyte as 1,000,000,000 bytes. The disk manufacturers are using the former system, which is technically more accurate but also has the side effects of making their disks look “bigger”. Vista, on the other hand uses the latter system, to make things easier for the user. So, you haven’t really lost any space, it’s just a different way of counting the same thing.