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 emin and a maximum emax)

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

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

       In addition to normalized floating-point numbers (f1>0 if x!=0), floating types might be able to contain other kinds of floating-point num-
       bers,  such as subnormal floating-point numbers (x!=0, e=emin, f1=0) and unnormalized floating-point numbers (x!=0, e=emin, f1=0), and val-
       ues 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
                operations 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 pmax radix b digits 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 number
            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, emin.

            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, emax.

            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**emin**-.

            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 5.10                                                          17 Dec 2003                                                     float.h(3HEAD)