C++ Variable scope, lifetime, and global variables

#include <iostream>
long count1 {999L};                    // Global count1
double count2 {3.14};                  // Global count2
int count3;                            // Global count3 - default intialization

int main() {//from www. ja  v  a  2s  .co m
  int count1 {10};                     // Hides global count1
  int count3 {50};                     // Hides global count3
  std::cout << "Value of outer count1 = " << count1 << std::endl;
  std::cout << "Value of global count1 = " << ::count1 << std::endl;
  std::cout << "Value of global count2 = " << count1 << std::endl;

  {                                    // New block scope starts here...
    int count1 {20};
    int count2 {30};
    std::cout << "\nValue of inner count1 = " << count1 << std::endl;
    std::cout << "Value of global count1 = " << ::count1 << std::endl;
    std::cout << "Value of inner count2 = " << count2 << std::endl;
    std::cout << "Value of global count2 = " << ::count2 << std::endl;

    count1 = ::count1 + 3;
    ++::count1;
    std::cout << "\nValue of inner count1 = " << count1 << std::endl;
    std::cout << "Value of global count1 = " << ::count1 << std::endl;
    count3 += count2;
  }

  std::cout << "\nValue of outer count1 = " << count1 << std::endl
            << "Value of outer count3 = " << count3 << std::endl;
    std::cout << "Value of global count3 = " << ::count3 << std::endl;

   std::cout << count2 << std::endl;
}