Double number representation

main.cpp

#include <cstdio>
#include <iostream>

using namespace std;

static union
{
   double use;
   char output[8];
};

void print_hex()
{
   char buffer[20];
   for (int i = 7; i >= 0; i--)
   {
      if (i < 7) putchar(' ');
      if (output[i] >= 0)
      {
         printf("%02x", int(output[i]));
      }
      else
      {
         sprintf(buffer, "%x", output[i]);
         putchar(buffer[6]);
         putchar(buffer[7]);
      }
   }
   putchar('\n');
}

void print_char(char c)
{
   for (int i = 7; i >= 0; i--)
   {
      if (c & (1 << i)) putchar('1');
      else putchar('0');
   }
}

void print_bin()
{
   print_char(output[7]);
   for (int i = 6; i >= 0; i--)
   {
      putchar(' ');
      print_char(output[i]);
   }
   putchar('\n');
}

void print()
{
   cout << use << '\n';
   print_hex();
   print_bin();
   putchar('\n');
}

int main()
{
   use = 3.0;
   print();

   use = -3.0;
   print();

   use = 127.9;
   print();

   use = 0.0;
   print();

   use = -0.0;
   print();

   double zero = 1.0 - 1.0;

   use = 0.0 / zero;
   print();

   use = 1.0 / zero;
   print();

   use = -1.0 / zero;
   print();

   system("pause");

   return 0;
}

output

3
40 08 00 00 00 00 00 00
01000000 00001000 00000000 00000000 00000000 00000000 00000000 00000000

-3
c0 08 00 00 00 00 00 00
11000000 00001000 00000000 00000000 00000000 00000000 00000000 00000000

127.9
40 5f f9 99 99 99 99 9a
01000000 01011111 11111001 10011001 10011001 10011001 10011001 10011010

0
00 00 00 00 00 00 00 00
00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

-0
80 00 00 00 00 00 00 00
10000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

-1.#IND
ff f8 00 00 00 00 00 00
11111111 11111000 00000000 00000000 00000000 00000000 00000000 00000000

1.#INF
7f f0 00 00 00 00 00 00
01111111 11110000 00000000 00000000 00000000 00000000 00000000 00000000

-1.#INF
ff f0 00 00 00 00 00 00
11111111 11110000 00000000 00000000 00000000 00000000 00000000 00000000