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

**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**and maximum_{min}**e**._{max}

Value of floating point = ± precision X base^{exponent}

**Macro constants**

Library 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*.

**FLT_RADIX:**Base for all floating-point typesMinimum value is 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

**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

**DECIMAL_DIG:**Decimal digits needed to represent floating-point valueNo Minimum value

**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

**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

**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

**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

**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

**FLT_MAX or DBL_MAX or LDBL_MAX:**Maximum finite representable floating-point number.Minimum value is 10

^{37}**FLT_EPSILON:**Difference between 1 and the least value greater than 1 that is representable.Maximum value is 10

^{-5}**DBL_EPSILON or LDBL_EPSILON:**Difference between 1 and the least value greater than 1 that is representable.Maximum value is 10

^{-9}**FLT_MIN or DBL_MIN or LDBL_MIN:**Minimum representable positive floating-point number.Maximum value is 10

^{-37}**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

**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.

`// 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; ` `} ` |

**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:** http://www.cplusplus.com/reference/cfloat/

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