<cfloat> float.h in C/C++ with Examples

• Sign Its value can be either negative or non-negative.
• Base It is also known as radix of exponent representation which represents different numbers with single number i.e. 2 for binary, 10 for decimal, 16 for hexadecimal, ...
• Mantissa It is also known as significand.It is a series of digits of the base. The number of digits in the series is known as precision.
• Exponent It is also known as characteristic is an integer between minimum e_min and maximum e_max.

Value of floating point = ± precision X base^exponent

1. FLT_RADIX: Base for all floating-point types

   Minimum value is 2

2. FLT_DIG: Number of decimal digits that can be rounded into a floating-point type and back again to the same decimal digits, without loss in precision.

   Minimum value is 6

3. DBL_DIG or LDBL_DIG: Number of decimal digits that can be rounded into a floating-point and back without change in the number of decimal digits.

   Minimum value is 10

4. DECIMAL_DIG: Decimal digits needed to represent floating-point value

   No Minimum value

5. FLT_MANT_DIG or DBL_MANT_DIG or LDBL_MANT_DIG: Precision of mantissa i.e. the number of digits that conform the significand.

   No Minimum value

6. FLT_MIN_EXP or DBL_MIN_EXP or LDBL_MIN_EXP: Minimum negative integer value for the exponent that generates a normalized floating-point number.

   No Minimum value

7. FLT_MIN_10_EXP or DBL_MIN_10_EXP or LDBL_MIN_10_EXP: Minimum negative integer value for the exponent of a base-10 expression that would generate a normalized floating-point number.

   Maximum value is -37

8. FLT_MAX_EXP or DBL_MAX_EXP or LDBL_MAX_EXP: Maximum integer value for the exponent that generates a normalized floating-point number.

   No Minimum value

9. FLT_MAX_10_EXP or DBL_MAX_10_EXP or LDBL_MAX_10_EXP: Maximum integer value for the exponent of a base-10 expression that would generate a normalized floating-point number.

   Minimum value is 37

10. FLT_MAX or DBL_MAX or LDBL_MAX: Maximum finite representable floating-point number.

    Minimum value is 1037

11. FLT_EPSILON: Difference between 1 and the least value greater than 1 that is representable.

    Maximum value is 10-5

12. DBL_EPSILON or LDBL_EPSILON: Difference between 1 and the least value greater than 1 that is representable.

    Maximum value is 10-9

13. FLT_MIN or DBL_MIN or LDBL_MIN: Minimum representable positive floating-point number.

    Maximum value is 10-37

14. FLT_ROUNDS: Rounds off the floating-point number Different possible values are:

    -1 : indeterminate
     0 : towards zero
     1 : towards one
     2 : towards positive infinity
     3 : towards negative infinity
    

15. FLT_EVAL_METHOD: Rounds off the floating-point number Different possible values are:

    -1 : undetermined
     0 : evaluate just to the range 
         and precision of the type
     1 : evaluate float and double as double,
         and long double as long double.
     2 : evaluate all as long double and Other 
         negative values indicate an 
         implementation defined behavior.
    

// C++ program to demonstrate working
// of macros constants in cfloat library

#include <cfloat>
#include <iostream>
using namespace std;

int main()
{
    cout << "FLT_RADIX : "
         << FLT_RADIX << endl;
    cout << "FLT_DIG : "
         << FLT_DIG << endl;
    cout << "DECIMAL_DIG : "
         << DECIMAL_DIG << endl;
    cout << "FLT_MIN_10_EXP : "
         << FLT_MIN_10_EXP << endl;
    cout << "FLT_MAX_EXP : "
         << FLT_MAX_EXP << endl;
    cout << "FLT_MAX_10_EXP : "
         << FLT_MAX_10_EXP << endl;
    cout << "FLT_MAX : "
         << FLT_MAX << endl;
    cout << "FLT_MIN : "
         << FLT_MIN << endl;
    return 0;
}

FLT_RADIX : 2
FLT_DIG : 6
DECIMAL_DIG : 21
FLT_MIN_10_EXP : -37
FLT_MAX_EXP : 128
FLT_MAX_10_EXP : 38
FLT_MAX : 3.40282e+38
FLT_MIN : 1.17549e-38