The multi threading concept in C++ with an example

The multi threading concept in C++ with an example:

#include
#include
using namespace std;
// function to be used in callable
void func_dummy(int N)
 {

  for (int i = 0; i < N; i++) {
  cout << "Thread 1 :: callable => function pointer\n";
   }

 }
 
// A callable object

class thread_obj {

 public:

   void operator()(int n) {

       for (int i = 0; i < n; i++)

           cout << "Thread 2 :: callable => function object\n";

   }

};

int main()
{
// Define a Lambda Expression
auto f = [](int n) {
   for (int i = 0; i < n; i++)
   cout << "Thread 3 :: callable => lambda expression\n";
   };
//launch thread using function pointer as callable
thread th1(func_dummy, 2);
// launch thread using function object as callable
thread th2(thread_obj(), 2);
//launch thread using lambda expression as callable
thread th3(f, 2);
// Wait for thread t1 to finish
 th1.join();
// Wait for thread t2 to finish
th2.join();
// Wait for thread t3 to finish
th3.join();
return 0;
}

Output:

Thread 1 :: callable => function pointer
Thread 1 :: callable => function pointer
Thread 3 :: callable => lambda expression
Thread 3 :: callable => lambda expression
Thread 2 :: callable => function object
Thread 2 :: callable => function object