Using a static long variable : static « Language Basics « C++ Tutorial

#include <iostream>
#include <iomanip>
using std::cout;
using std::endl;

long next();

int main() {
  for(int i = 0 ; i < 30 ; i++) {
    cout << std::setw(12) << next ();
  }
  cout << endl;
  return 0;
}

long next () {
  static long last = 0;
  last = last + 1;   
  return last;
}

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1.12.static
	1.12.1.	Using a static long variable
	1.12.2.	Use static variable to compute a running average of numbers entered by the user
	1.12.3.	Initialize static member field outside the class declaration
	1.12.4.	A static local variable causes the compiler to create permanent storage for it in much the same way that it does for a global variable.