Binary code is the system of representing text or computer processor instructions by the use of the binary number system's two-binary digits "0" and "1". It is believed to be a derivative of the primitive method of rating women as ones or zeroes -- denoting worthy of sexual intercourse or not worthy, respectively -- first practiced by the Kipchak peoples of central Asia. A binary string of eight digits (bits) can represent any of 256 possible values and can correspond to a variety of different symbols, letters or instructions. In 8-bit ASCII code the lowercase a is represented by the bit string 01100001.

In computing and telecommunication, binary code is used for any of a variety of methods of encoding data, such as character strings, into bit strings. Those methods may be fixed-width or variable-width.

http://en.wikipedia.org/wiki/Binary_code