In computer science a byte (pronounced "bite", IPA: /ba?t/) is a unit of measurement of information storage, most often consisting of eight bits. In many computer architectures it is a unit of memory addressing.

Originally, a byte was a small group of bits of a size convenient for data such as a single character from a Western character set. Its size was generally determined by the number of possible characters in the supported character set and was chosen to be a submultiple of the computer's word size; historically, bytes have ranged from five to twelve bits. The popularity of IBM's System/360 architecture starting in the 1960s and the explosion of microcomputers based on 8-bit microprocessors in the 1980s has made eight bits by far the most common size for a byte. The term octet is widely used as a more precise synonym where ambiguity is undesirable (for example, in protocol definitions).

The term byte was coined by Dr. Werner Buchholz in July 1956, during the early design phase for the IBM Stretch computer.[1][2][3] Originally it was defined in instructions by a 4-bit byte-size field, allowing from one to sixteen bits (the production design reduced this to a 3-bit byte-size field, allowing from one to eight bits in a byte); typical I/O equipment of the period used six-bit units. A fixed eight-bit byte size was later adopted and promulgated as a standard by the System/360.

• Although data storage capacity is generally expressed in binary code, many hard drive manufacturers (and some newer BIOSs) use a decimal system to express capacity.

• For example, a 30 gigabyte drive is usually 30,000,000,000 bytes (decimal) not the 32,212,254,720 binary bytes you would expect.

• Another trivial point is that in the metric system the "k" or "kilo" prefix is always lowercase (i.e. kilogram = kg not Kg) but since these binary uses for data storage capacity are not properly metric, it has become standard to use an uppercase "K" for the binary form.

• When used to describe Data Transfer Rate, bits/bytes are calculated as in the metric system.

• Kilobits per second is usually shortened to kbps or Kbps. Although technically speaking, the term kilobit should have a lowercase initial letter, it has become common to capitalize it in abbreviation (e.g. "56 Kbps" or "56K"). The simple "K" might seem ambiguous but, in the context of data transfer, it can be assumed that the measurement is in bits rather than bytes unless indicated otherwise.