Units of data are based on bits (binary digits). A bit can have two states (0 or 1) and is the basis of binary computing. A byte is conventionally eight (8) bits. Since each bit can have two states, the total number of states in a byte is 2x2x2x2x2x2x2x2 or 2^{8} or 256 states. Before long the number of possible states becomes unmanageable large. For example, 1 kilobit can have 2^{1000} possible states (or more than 1 followed by 301 zeros). Converting between the various information units is very important when evaluating internet speeds and data (traffic) allowances. Connection speeds are usually quoted in megabits per sec (Mbps) but most of us are familiar with megabytes (MBs). A connection speed of 8 megabits per second is equivalent to one megabyte per second. Very high data transfer rates are possible with optical fibre and this is the proposed technology for Australia's National Broadband Network (NBN). Data storage is usually quoted in terabytes and computer memory (RAM) in gigabytes.
The blue and yellow boxes at the top are the SI standard units and they use base 10. The powers of ten appear in the rightmost column. Mega is 10^{6}, for example. These are standard SI prefixes for the familiar powers of ten that increment by three powers (i.e. standard SI prefix + either bit or byte). The orange and green units at the bottom use binary multiples. This is because computers use binary and some measures still use these powers of two. 2^{10} (1024) approximates 10^{3} (1000) and this is what the kibibyte is and is close in value to the kilobyte. These binary equivalents go up in multiples of 2^{10} and they become increasingly distant from their SI equivalents as they get larger. This is because you have to multiply by 1024 each time instead of 1000. You can check out these powers using our powers calculator. For example, Mebi means 2^{20}. See the National Institute of Standards.
