#include <iostream>

int main()
{
  union IEEE754SinglePrecisionFloat // Warning! non-portable code
  {
    float f;
    struct 
    {
      unsigned mantisse : 23;
      unsigned exponent : 8;
      unsigned sign     : 1;
    } bits;
  } x;

  // ... f == pow(-1, sign) * mantisse * pow(2, exponent-127)

  x.bits.sign     = 1;
  x.bits.exponent = 130;     
  x.bits.mantisse = 0x10000;

  float y = x.f;  // -8.0625 ???
  std::cout << y << '\n';
}