<cfloat> float.h in C/C++ with Examples (original) (raw)

Last Updated : 12 Jul, 2025

This header file consists of platform-dependent and implementation specific floating point values. A floating point has four parts.

• SignIts value can be either negative or non-negative.
• BaseIt 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, ...
• MantissaIt 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.
• ExponentIt is also known as characteristic is an integer between minimum emin and maximum emax.

Value of floating point = ± precision X baseexponent

Macro constantsLibrary macros are hardware-specific values for the floating-point types.FLT implies type float, DBL implies double, and LDBL implies long double, DIG implies digits, MANT implies mantissa, EXP implies 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.

Below is the program to demonstrate the working of macros constants in cfloat library.

CPP `

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

#include #include 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; }

`

Output (Machine Dependent):

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

Reference: https://cplusplus.com/reference/cfloat/