rand() - Same Ten Digits Printed -- Random?

[Deluge]

I must be using the rand() function wrong, because every time I run this program, even after recompiling, it prints out the same ten digits:

3675356291

code:

#include <iostream>
#include <cstdlib>
using namespace std;

class Random
{
  public:
    int getnumber(); // Retrieve a random number
};

int Random::getnumber()
{
  int random = rand() % 10;
  return random;
}

int main()
{
  Random num;
  
  for (int x = 0; x < 10; x += 1)
  {
    cout << num.getnumber(); // Print a random number
    cout.flush(); // Clear output buffer
    usleep(100000); // Wait 1/10 sec between numbers
  }
  cout << endl;
  
  return 0;
}

Why aren't the numbers randomly chosen each time the program is run? The compiler seems to predefine the numbers.

[z05DSL3A]

You need to seed the RNG with srand()
http://www.cplusplus.com/reference/clibrary/cstdlib/srand/

#include <iostream>
#include <cstdlib>
#include <time.h>
using namespace std;

class Random
{
  public:
    int getnumber(); // Retrieve a random number
    static void seed(unsigned int seed  = time(NULL)  )
        {
            srand (seed);
        };
};

int Random::getnumber()
{
  int random = rand() % 10;
  return random;
}

int main()
{
  Random::seed();
  Random num;
  
  for (int x = 0; x < 10; x += 1)
  {
    cout << num.getnumber(); // Print a random number
    cout.flush(); // Clear output buffer
  }
  cout << endl;
  
  return 0;
}

edit:
The following would mean that you would not have to remeber to seed the RNG

#include <iostream>
#include <cstdlib>
#include <time.h>
using namespace std;

class Random
{
  public:
    int getnumber(); // Retrieve a random number
private:
    static bool seeded;
};

bool Random::seeded = false;

int Random::getnumber()
{
    if(!seeded)
    {
        srand((unsigned int) time(NULL) );
        seeded = true;
    }
    int random = rand() % 10;
    return random;
}

int main()
{
  Random num;
  
  for (int x = 0; x < 10; x += 1)
  {
    cout << num.getnumber(); // Print a random number
    cout.flush(); // Clear output buffer
  }
  cout << endl;
  
  return 0;
}

[Deluge]

Thank you very much.