floating-point

    A number representation consisting
   of a mantissa, M, an exponent, E, and a radix (or
   "base").  The number represented is M*R^E where R is the
   radix.

   In science and engineering, exponential notation or
   scientific notation uses a radix of ten so, for example, the
   number 93,000,000 might be written 9.3 x 10^7 (where ^7 is
   superscript 7).

   In computer hardware, floating point numbers are usually
   represented with a radix of two since the mantissa and
   exponent are stored in binary, though many different
   representations could be used.  The IEEE specify a
   standard representation which is used by many hardware
   floating-point systems.  Non-zero numbers are normalised so
   that the binary point is immediately before the most
   significant bit of the mantissa.  Since the number is
   non-zero, this bit must be a one so it need not be stored.  A
   fixed "bias" is added to the exponent so that positive and
   negative exponents can be represented without a sign bit.
   Finally, extreme values of exponent (all zeros and all ones)
   are used to represent special numbers like zero and positive
   and negative infinity.

   In programming languages with explicit typing,
   floating-point types are introduced with the keyword "float"
   or sometimes "double" for a higher precision type.

   See also floating-point accelerator, floating-point unit.

   Opposite: fixed-point.

   (2008-06-13)