#include<iostream> 
 
using namespace std; 
 
 
int add(int x, int y) 
 {
int r;
r = x+y;
return (r); 
 }  
 
 
int main () 
{ 
int x, y ;
 
cout << "Welcome to the Functions Program! To quit enter 0." << endl ;
cout << "Input two numbers." << endl ;
cin >> x >> y ;
 
 
while (x != 0 || y != 0) 
 {
int z ; 
z = add(x,y); 
cout << "The result is " << z;  
cout << "Would you like to continue? If so enter another two numbers, if not enter 0" << endl ;
cin >> x >> y ; 
}
 
}

#include <iostream> 
using namespace std; 

int add(int x, int y) {
  int r;
  r = x + y;
  return(r); 
}  

int main () { 
  int x, y;

  cout << "Welcome to the Functions Program! To quit enter 0." << endl;
  cout << "Input two numbers." << endl;
  cin >> x >> y;

  while (x != 0 || y != 0) {
    int z = add(x, y); 
    cout << "The result is " << z;  
    cout << "\nWould you like to continue? If so enter another two numbers, if not enter 0" << endl;
    cin >> x >> y ; 
  }
}

#include<iostream>
 
using namespace std;
 
int add(int x, int y)
{
int r ;
r = x+y ;
return (r) ;
}
 
int sub(int x, int y)
{
int w ;
w = x-y;
return (w) ;
}
 
int mult(int x, int y)
{
int b;
b = x*y ;
return (b) ;
}
 
int div(int x, int y)
{
int q;
q = x/y;
return (q);
}
 
 
int main()
{
int x,y,z;
 
cout << "Welcome to the Functions program! To exit at anytime enter 0." << endl ;
cout << "Input two numbers." << endl;
cin >> x >> y ;
cout << "Now enter 1 to add, 2 to subtract, 3 to multipy, 4 to divide" << endl ;
cin >> z ;

switch ( z ) {
 case 1: // Add
   {
   }
   break;
 case 2: // Subtract
   {
   }
   break;
 case 3: // Multiply
   {
   }
   break;
 case 4: // Divide
   {
   }
   break;
}

switch ( z ) 
	 {
      case 1: //add
       sum = add(x,y);
       cout << "Your sum is: " << sum << endl;
       break;
      case 2: // Subtract
       sum = sub(x,y);
       cout << "Your sum is: " << sum << endl;
       break;
      case 3: // Multiply
       sum = mult(x,y);
       cout << "Your sum is: " << sum << endl;
       break;
      case 4: // Divide
       sum = divi(x,y);
       cout << "Your sum is: " << sum << endl;
       break;
 
	 }
 
	  while (x != 0 || y != 0)
	  {
	      cout << "Would you like to continue? If so enter two more numbers." << endl;
              cout << "Otherwise enter 0's." << endl ;
	      cin >> x >> y ;
	      cout << "Which Operation?" << endl ;
	      cin >> z ;
	  }
 
	 }

do
{
    get option ( 1,2,3,4 or 0 to quit)
    if( option not 0 )
    {
        get inputs (x and y)
 
        switch( option )
       {
           //cases 1-4 as you've done
          default:  //bad input message
        }
     }
  }while ( option not 0 );