Write a program to implement the concept of singleton pattern.

#include<iostream.h>
#include<conio.h>
class GlobalClass
{
    int m_value;
    static GlobalClass *s_instance;
    GlobalClass(int v = 0)
    {
m_value = v;
    }
  public:
    int get_value()
    {
return m_value;
    }
    void set_value(int v)
    {
m_value = v;
    }
    static GlobalClass *instance()
    {
if (!s_instance)
 s_instance = new GlobalClass;
return s_instance;
    }
};

// Allocating and initializing GlobalClass's
// static data member.  The pointer is being
// allocated - not the object inself.

GlobalClass *GlobalClass::s_instance = 0;

void foo(void)
{
  GlobalClass::instance()->set_value(1);
  cout << "foo: global_ptr is " << GlobalClass::instance()->get_value() << '\n';
}

void bar(void)
{
  GlobalClass::instance()->set_value(2);
  cout << "bar: global_ptr is " << GlobalClass::instance()->get_value() << '\n';
}

int main()
{
  clrscr();
  cout << "main: global_ptr is " << GlobalClass::instance()->get_value() << '\n';
  foo();
  bar();
  getch();
  return 0;
}