typedef union {
  float value;
  struct {
    unsigned int mantissa:23;
    unsigned int exponent:8;
    unsigned int negative:1;
  };
} ieee754_float_t;

ieee754_float_t f = (ieee754_float_t) 42.f;
printf("mantissa = %u, exponent = %u, negative = %u", f.mantissa, f.exponent, f.negative);
// mantissa = 2621440, exponent = 132, negative = 0