Originally posted by: joshg
Actually, your hard drive is 20 billion bytes (or, 20000000000 bytes). Not truly 20 gigabytes.
Here's an easy way to look at it: Each conversion of *byte to the level of larger capacity is divided by 1024 (meaning that there are 1024
bytes in one kilobyte, 1024
kilobytes in one megabyte, etc. etc....)
Therefore, whenever you convert your 20 billion bytes into a gigabyte format, you get:
20000000000 BYTES / 1024 = 19531250 KILOBYTES
19531250 KILOBYTES / 1024 = 19073.486328125 MEGABYTES
19073.486328125 MEGABYTES / 1024 = 18.6264514923095703125 GIGABYTES
and, 18.6264514923095703125 ~= 18.6
You didn't "lose" 3 GB, you are just seeing the capacity of your 20 billion-byte hard drive formatted to show in GB instead of bytes.