The header file <float.h> defines macros that expand to various limits and parameters of the standard floating point types.

Implementation
FLT_ROUNDS | The rounding mode for floating point addition.
FLT_RADIX | The radix of the exponent representation
FLT_MANT_DIG | The number of base FLT_RADIX digits in the mantissa part of a float
DBL_MANT_DIG | The number of base FLT_RADIX digits in the mantissa part of a double
FLT_DIG | The number of digits of precision of a float
DBL_DIG | The number of digits of precision of a double
Float exponent minimum and maximum values
FLT_MIN_EXP | The minimum value of base FLT_RADIX in the exponent part of a float
FLT_MIN_10_EXP | The minimum value of base 10 in the exponent part of a float
FLT_MAX_EXP | The maximum value of base FLT_RADIX in the exponent part of a float
FLT_MAX_10_EXP | The maximum value of base 10 in the exponent part of a float
Double exponent minimum and maximum values
DBL_MIN_EXP | The minimum value of base FLT_RADIX in the exponent part of a double
DBL_MIN_10_EXP | The minimum value of base 10 in the exponent part of a double
DBL_MAX_EXP | The maximum value of base FLT_RADIX in the exponent part of a double
DBL_MAX_10_EXP | The maximum value of base 10 in the exponent part of a double
Float minimum and maximum values
FLT_MIN | The minimum value of a float
FLT_EPSILON | The minimum positive number such that 1.0 + FLT_EPSILON != 1.0
FLT_MAX | The maximum value of a float
Double minimum and maximum values
DBL_MIN | The minimum value of a double
DBL_EPSILON | The minimum positive number such that 1.0 + DBL_EPSILON != 1.0
DBL_MAX | The maximum value of a double