// Simple program
#include <iostream>
using namespace std;
int main()
{
    int x, y;

    x = 2;
    y = x + 4;
    cout <<" x = "<<x<<"  x + 4 = "<<y << endl;

    return 0;
}

Output:

 x = 2  x + 4 = 6

=========================================================

// Simple Input and output
#include <iostream>
using namespace std;
int main ()
{
int a, b;
   cout << " enter two integers:";
   cin >> a >> b;
   cout << " a = " << a
        << " b = " << b << endl;
return 0;
}


Output:

 enter two integers:2 7
 a = 2 b = 7

=========================================================

//example: a programmer-defined function
#include <iostream>
using namespace std;
int square( int );   // function prototype
int main()
{
   for ( int x = 1; x <= 10; x++ )
      cout << square( x ) << "  ";
   cout << endl;
   return 0;
}
// Function definition
int square( int y )
{
   int result;
   result = y * y;
   return result;
}

Output:

1  4  9  16  25  36  49  64  81  100

=========================================================

// test on global and local variables
#include <iostream>
using namespace std;
void f12(void);
int nglobal = 1;
main()
{
  cout << "main 1: nglobal = " << nglobal <<endl;
  nglobal = 2;
  cout << "main 2: nglobal = " << nglobal <<endl;
  f12();
  cout << "main 3: nglobal = " << nglobal <<endl;

}
void f12()
{
  cout << "f12   : nglobal = " << nglobal <<endl;
  nglobal = 3;
}

Output:

main 1: nglobal = 1
main 2: nglobal = 2
f12   : nglobal = 2
main 3: nglobal = 3

=========================================================
//example: a "void" case
#include <iostream>
using namespace std;
void out2( void );   // function prototype
int main()
{
   out2();
   return 0;
}
// Function definition
void out2(void)
{
   cout << "output from function out2";
   return;
}


Output:

output from function out2

=========================================================

// using the break statement
#include <iostream>
using namespace std;
int main ()
{
int n;
for (n = 1; n <=10; n = n+1)
{
   if (n == 5)
      break;
   cout << n << "  ";
}
cout << "\nBroke out of loop at n of " << n;
return 0;
}

Output:

1  2  3  4
Broke out of loop at n of 5

=========================================================

// Using the continue statement in a for structure
#include <iostream>
using namespace std;
int main()
{
    for ( int x=1; x<=10; x++)
    {
        if (x == 5)
        {
            continue;
        }
        cout << x << " ";
    }
    cout << "\nUsed continue to skip printing 5" << endl;
    return 0;
}

Output:

1 2 3 4 6 7 8 9 10
Used continue to skip printing 5

=========================================================

// conditional operator
#include <iostream>
using namespace std;

int main ()
{
int a,b,c;
a=2;
b=7;
c = (a>b) ? a : b;
cout << " c = " << c;
return 0;
}

Output:

 c = 7

=========================================================
// call-by-reference
#include <iostream>
using namespace std;

void f12(int&, int&);
int main()
{
   int a, b;
   a = 12;
   b = a;
   cout << "a = "<< a << "  b = " << b <<endl;
   f12(a, b);
   cout << "a = "<< a << "  b = " << b <<endl;
   return 0;
}
void f12(int& out1, int& out2)
{
    out1 = out1*2.0;
    out2 = out1 +3;
}

Output:

a = 12  b = 12
a = 24  b = 27

=========================================================

// test functions passing many results
// call-by-value
// call-by-reference
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

void f12(double, double&, double&);
int main()
{
   double a, b, c;
   a = 12.0;
   cout << a <<endl;
   f12(a, b, c);
   cout << a <<endl;
   cout << b <<endl;
   cout << c <<endl;
   return 0;
}
void f12(double inp, double& out1, double& out2)
//void f12(double& inp, double& out1, double& out2)
{
    out1 = inp*2.0;
    out2 = inp*3.0;
}

Output:

12
12
24
36

=========================================================

//example: using function pointers
#include <iostream>
using namespace std;
float av( float, float, float(*)(float));
float x2(float);
int main()
{ float x2average, xmin, xmax;
    xmin = 2.0;
    xmax = 4.0;
    x2average = av(xmin, xmax, x2);
    cout << "average = " << x2average;
    return 0;
}

float av( float a, float b, float (*f) (float) )
{
    return (f(b)+f(a))/2.0;
}
float x2 (float x)
{
    return x*x;
}


Output:

average = 10