#include <stdio.h>
 
typedef struct
{
    signed short m;
    unsigned char f;
} Q16_8;
 
Q16_8 toQ(double d)
{
    Q16_8 q;
    long x = d * 256;
    q.m = x / 256; // this assumes >> to be an arithmetic shift
    q.f = x & 0xFF; // this assumes signed ints to be 2's complement
    return q;
}
 
double toDouble(Q16_8 q)
{
    long x = ((long)q.m << 8) + q.f;
    return x / 256.0;
}
 
int main(void)
{
  int i;
  for (i = -2*4; i <= +2*4; i++)
  {
    double d = i / 4.0;
    Q16_8 q = toQ(d);
    double d2 = toDouble(q);
    printf("toDouble(toQ(%f)) = %f\n", d, d2);
  }
  return 0;
}
 

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