Orders of magnitude (data)
An order of magnitude is usually a factor of ten. Thus, four orders of magnitude are a factor of 10,000 or 10. This article presents a list of multiples, sorted by orders of magnitude, for units of information measured in bits and bytes. The byte is a common unit of measurement of information (kilobyte, kibibyte, megabyte, mebibyte, gigabyte, gibibyte, terabyte, tebibyte, etc.). For the purpose of this article, a byte is a group of 8 bits (octet), a nibble is a group of four bits. Historically, both assumptions have not always been true. The decimal SI  prefixes "kilo", "mega", "giga", "tera", etc., are powers of . The binary prefixes "kibi", "mebi", "gibi", "tebi", etc. respectively refer to the corresponding power of . In casual usage, when 1024 is a close enough approximation of 1000, the two corresponding prefixes are treated as equivalent. For most purposes programmers do not distinguish the two as it would be impractical to divide memory in decimal chunks, so it is assumed that affixes (k,m,g,T) represent the binary counterparts of (2^10, 2^20, 2^30, 2^40) respectively. The distinction is made when communicating with disciplines  where the decimal prefix is important, for example in hardware such as in denoting device capacity or data transfer rates. This can lead to some confusion when software displays a binary quantity with a decimal prefix. For example an operating system may describe the number of gibibyte remaining on a volume, but use the suffix GB for historical reasons. Note: this page mixes between two kinds of entropies: These two definitions are not entirely equivalent, see Entropy in thermodynamics and information theory. For comparison, the Avogadro constant is entities per mole, based upon the number of atoms in 12 grams  of carbon-12 isotope. In 2012, some hard disks used ~984,573 atoms to store each bit. In January 2012, IBM researchers announced they compressed 1 bit in 12 atoms using antiferromagnetism and a scanning tunneling microscope with iron and copper atoms. This could mean a practical jump from a disk to a disk.