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In the floating-point case, a variable exponent would represent the power of ten to which the mantissa of the number is multiplied. Languages that support a rational data type usually allow the construction of such a value from two integers, instead of a base-2 floating-point number, due to the loss of exactness the latter would cause.
The arithmetical difference between two consecutive representable floating-point numbers which have the same exponent is called a unit in the last place (ULP). For example, if there is no representable number lying between the representable numbers 1.45a70c22 hex and 1.45a70c24 hex, the ULP is 2×16 −8, or 2 −31.
Several earlier 16-bit floating point formats have existed including that of Hitachi's HD61810 DSP of 1982 (a 4-bit exponent and a 12-bit mantissa), [2] Thomas J. Scott's WIF of 1991 (5 exponent bits, 10 mantissa bits) [3] and the 3dfx Voodoo Graphics processor of 1995 (same as Hitachi).
The same value can also be represented in scientific notation with the significand 1.2345 as a fractional coefficient, and +2 as the exponent (and 10 as the base): 123.45 = 1.2345 × 10 +2. Schmid, however, called this representation with a significand ranging between 1.0 and 10 a modified normalized form. [12] [13] For base 2, this 1.xxxx form ...
Double-precision floating-point format (sometimes called FP64 or float64) is a floating-point number format, usually occupying 64 bits in computer memory; it represents a wide range of numeric values by using a floating radix point.
Logarithm in base 2 is relatively straightforward, as the integer part k is already in the floating-point exponent; a preliminary range reduction is accordingly performed, yielding k. The mantissa x (where log2( x ) is between -1/2 and 1/2) is then compared to a table and intervals for further reduction into a z with known log2 and an in-range ...
In the case of the mechanical calculators, the exponent is often treated as side information that is accounted for separately. The IBM 650 computer supported an 8-digit decimal floating-point format in 1953. [1] The otherwise binary Wang VS machine supported a 64-bit decimal floating-point format in 1977. [2]
This alternative definition is significantly more widespread: machine epsilon is the difference between 1 and the next larger floating point number.This definition is used in language constants in Ada, C, C++, Fortran, MATLAB, Mathematica, Octave, Pascal, Python and Rust etc., and defined in textbooks like «Numerical Recipes» by Press et al.