C++双精度浮点格式，仅供参考

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>

typedef union
{
   double f;
   uint32_t i[2];
}Packet;

#define M  ((1<<20)-1)
void test( double f)
{
  Packet p;
  p.f=f;
  printf("f1 = %.16f ~= (1.0+%u/2^20)*2^%u\n", p.f, p.i[1]&M, (p.i[1]>>20)-1023 );
}

int main(int argc, char* argv[] )
{
   double f;
   printf("Please input a double?");
   scanf("%lf",&f);
   test(f);
   return 0;
}