Functions, Side effects Understanding scope in c++ pro

Converting value-returning functions to void functions

#include 

#include

int inc (int);

void main () 

{

  int i = 3;

  int j;

  j = inc (i);

  cout << j << endl;

}

int inc (int a) 

{

  return(a+1);

}

Bad style, side-effects, value-returning

#include 

#include

int counter = 0;

int add (int&, int&);

void main () 

{

  int i, j, sum;

  i = 7; j = 17;

  sum = add(i,j);

  cout << "counter = " << counter << ", i = " << i << ", j = " << j 

    << ", sum = " << sum << endl;

  i = 7; j = 17;

  sum = add(i,j);

  cout << "counter = " << counter << ", i = " << i << ", j = " << j 

    << ", sum = " << sum+i+j+counter << endl;

  i = 7; j = 17;

  sum = i+j+counter;

  cout << "counter = " << counter << ", i = " << i << ", j = " << j 

    << ", sum = " << sum+add(i,j) << endl;

  i = 7; j = 17;

  sum = add(i,i);

  cout << "counter = " << counter << ", i = " << i << ", j = " << j 

    << ", sum = " << sum << endl;

}

int add (int& a, int& b) 

{

  int temp, sum;

  sum = a+b;

  temp = a;

  a = b+1;

  b = temp+1;

  counter = counter + 1;

  return(sum);

}

Understanding scope

#include 

#include

void f ();

int i = 0;

void main () 

{ 

  cout << i << endl;  

  int i = 1;

  cout << i << endl;

  { 

    int i = 2;

    cout << i << endl;

    { 

      int i = 3;

      cout << i << endl;

      { 

   int i = 4;

   cout << i << endl;

      }

      cout << i << endl;

    }

    cout << i << endl;

  }

  cout << i << endl;

  f(); f(); f();

}

void f () 

{

  cout << i << endl;

  static int i = 5;

  cout << i++ << endl;

}