float.h(3HEAD)							      Headers							    float.h(3HEAD)

NAME

       float.h, float - floating types

SYNOPSIS

       #include <float.h>

DESCRIPTION

       The  characteristics of floating types are defined in terms of a model that describes a representation of floating-point numbers and values
       that provide information about an implementation's floating-point arithmetic.

       The following parameters are used to define the model for each floating-point type:

       s     sign (+-1)

       b     base or radix of exponent representation (an integer >1)

       e     exponent (an integer between a minimum e(min) and a maximum e(max))

       p     precision (the number of base-b digits in the significand)

       f(k)  non-negative integers less than b (the significand digits)

       In addition to normalized floating-point numbers (f(1)>0 if x!=0), floating types might be able to contain other  kinds	of  floating-point
       numbers,  such  as  subnormal  floating-point  numbers  (x!=0,  e=e(min),  f(1)=0) and unnormalized floating-point numbers (x!=0, e=e(min),
       f(1)=0), and values that are not floating-point numbers, such as infinities and NaNs. A NaN is an encoding signifying Not-a-Number. A quiet
       NaN  propagates	through  almost  every arithmetic operation without raising a floating-point exception; a signaling NaN generally raises a
       floating-point exception when occurring as an arithmetic operand.

       The accuracy of the library functions in math.h(3HEAD) and complex.h(3HEAD) that return floating-point results is defined on the libm(3LIB)
       manual page.

       All  integer  values in the <float.h> header, except FLT_ROUNDS, are constant expressions suitable for use in #if preprocessing directives;
       all floating values are constant expressions. All except DECIMAL_DIG, FLT_EVAL_METHOD, FLT_RADIX, and FLT_ROUNDS have  separate	names  for
       all three floating-point types. The floating-point model representation is provided for all values except FLT_EVAL_METHOD and FLT_ROUNDS.

       The rounding mode for floating-point addition is characterized by the value of FLT_ROUNDS:

       -1    Indeterminable.

       0     Toward zero.

       1     To nearest.

       2     Toward positive infinity.

       3     Toward negative infinity.

       The values of operations with floating operands and values subject to the usual arithmetic conversions and of floating constants are evalu-
       ated to a format whose range and precision might be greater than required by the type. The use of evaluation formats  is  characterized	by
       the architecture-dependent value of FLT_EVAL_METHOD:

       -1    Indeterminable.

       0     Evaluate all operations and constants just to the range and precision of the type.

       1     Evaluate operations and constants of type float and double to the range and precision of the double type; evaluate long double opera-
	     tions and constants to the range and precision of the long double type.

       2     Evaluate all operations and constants to the range and precision of the long double type.

       The values given in the following list are defined as constants.

	   o	  Radix of exponent representation, b.

		    FLT_RADIX

	   o	  Number of base-FLT_RADIX digits in the floating-point significand, p.

		    FLT_MANT_DIG
		    DBL_MANT_DIG
		    LDBL_MANT_DIG

	   o	  Number of decimal digits, n, such that any floating-point number in the widest supported floating type with p(max) radix b  dig-
		  its can be rounded to a floating-point number with n decimal digits and back again without change to the value.

		    DECIMAL_DIG

	   o	  Number of decimal digits, q, such that any floating-point number with q decimal digits can be rounded into a floating-point num-
		  ber with p radix b digits and back again without change to the q decimal digits.

		    FLT_DIG
		    DBL_DIG
		    LDBL_DIG

	   o	  Minimum negative integer such that FLT_RADIX raised to that power minus 1 is a normalized floating-point number, e(min).

		    FLT_MIN_EXP
		    DBL_MIN_EXP
		    LDBL_MIN_EXP

	   o	  Minimum negative integer such that 10 raised to that power is in the range of normalized floating-point numbers.

		    FLT_MIN_10_EXP
		    DBL_MIN_10_EXP
		    LDBL_MIN_10_EXP

	   o	  Maximum integer such that FLT_RADIX raised to that power minus 1 is a representable finite floating-point number, e(max).

		    FLT_MAX_EXP
		    DBL_MAX_EXP
		    LDBL_MAX_EXP

	   o	  Maximum integer such that 10 raised to that power is in the range of representable finite floating-point numbers.

		    FLT_MAX_10_EXP
		    DBL_MAX_10_EXP
		    LDBL_MAX_10_EXP

       The values given in the following list are defined as constant expressions with values that are greater than or equal to those shown:

	   o	  Maximum representable finite floating-point number.

		    FLT_MAX
		    DBL_MAX
		    LDBL_MAX

       The values given in the following list are defined as constant expressions with implementation-defined (positive) values that are less than
       or equal to those shown:

	   o	  The difference between 1 and the least value greater than 1 that is representable in the given floating-point type, b^1 - p.

		    FLT_EPSILON
		    DBL_EPSILON
		    LDBL_EPSILON

	   o	  Minimum normalized positive floating-point number, b^e(min)^-1.

		    FLT_MIN
		    DBL_MIN
		    LDBL_MIN

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       complex.h(3HEAD), math.h(3HEAD), attributes(5), standards(5)

SunOS 5.11							    17 Dec 2003 						    float.h(3HEAD)