The kilobyte is a multiple of the unit byte for digital information. The International System of Units (SI) defines the prefix kilo as 1000 (103); therefore one kilobyte is 1000 bytes. The unit symbol for the kilobyte is kB. In information technology, particularly in reference to main memory capacity, kilobyte is traditionally used to denote 1024 (210) bytes. This arises from the powers-of-two sizing common to such memory in digital circuitry. In this context, the symbols K and KB are often used when 1024 bytes is meant.