(Greatest Common Divisor) The greatest common divisor (GCD) of two integers is the largest integer that evenly divides each of the numbers. Write a function gcd that returns the greatest com- mon divisor of two integers.

What will be an ideal response?

```
// Finds greatest common divisor (GCD) of 2 inputs.
#include
using namespace std;

int gcd( int, int ); // function prototype

int main()
{
int a; // first number
int b; // second number
// loop for 5 pairs of inputs
for ( int j = 1; j <= 5; j++ )
{
cout << "Enter two integers: ";
cin >> a >> b;

cout << "The greatest common divisor of "
<< a << " and " << b << " is ";

// find greatest common divisor of a and b
cout << gcd( a, b ) << endl;
} // end for
} // end main

// gcd finds greatest common divisor of x and y
int gcd( int x, int y )
{
int greatest = 1; // current greatest common divisor, 1 is minimum

// loop from 2 to smaller of x and y
for ( int i = 2; i <= ( ( x < y ) ? x: y ); i++ )
{
// if current i divides both x and y
if ( x % i == 0 && y % i == 0 )
greatest = i; // update greatest common divisor
} // end for

return greatest; // return greatest common divisor found
} // end function gcd
```