The "float.h" header file in C programming provides information about the implementation-defined characteristics of the floating-point arithmetic used by the implementation.

Here are some of the commonly used macros defined in the "float.h" header file:

1. "FLT_RADIX": The base of the exponent for the floating-point representation.

2. "FLT_ROUNDS": The rounding mode used for floating-point arithmetic.

3. "FLT_EPSILON": The smallest positive floating-point value such that 1.0 + epsilon != 1.0.

4. "FLT_DIG": The number of decimal digits that can be represented without loss of precision by the float data type.

5. "FLT_MANT_DIG": The number of binary digits (bits) in the significand (mantissa) of the float data type.

6. "FLT_MAX": The maximum finite value that can be represented by the float data type.

7. "FLT_MIN": The minimum positive normalized value that can be represented by the float data type.

Here is an example of using the "float.h" header file in a C program:

#include <stdio.h>
#include <float.h>

int main() {
    printf("FLT_RADIX: %d\n", FLT_RADIX);
    printf("FLT_ROUNDS: %d\n", FLT_ROUNDS);
    printf("FLT_EPSILON: %e\n", FLT_EPSILON);
    printf("FLT_DIG: %d\n", FLT_DIG);
    printf("FLT_MANT_DIG: %d\n", FLT_MANT_DIG);
    printf("FLT_MAX: %e\n", FLT_MAX);
    printf("FLT_MIN: %e\n", FLT_MIN);

    return 0;
}

In this example, the "float.h" header file macros are used to print information about the implementation-defined characteristics of the floating-point arithmetic used by the implementation to the console. The output of the program will vary depending on the specific implementation and platform.