Unary Scope Resolution Operator ::

It is possible to declare local and global variables of the same name. C++ provides the unary scope resolution operator (::) to access a global variable when a local variable of the same name is in scope. The unary scope resolution operator cannot be used to access a local variable of the same name in an outer block. A global variable can be accessed directly without the unary scope resolution operator if the name of the global variable is not the same as that of a local variable in scope.

Unary scope resolution operator

1  // Fig. 6.23: fig06_23.cpp
 2  // Using the unary scope resolution operator.
 3  #include <iostream>
 4  using std::cout;
 5  using std::endl;
 6
 7  int number = 7; // global variable named number
 8
 9  int main()
10  {
11     double number = 10.5; // local variable named number
12
13     // display values of local and global variables
14     cout << "Local double value of number = " << number // prints 10.5
15        << "\nGlobal int value of number = " << ::number << endl; // prints 7
16     return 0; // indicates successful termination
17  } // end main