What is the output of the following C++ code? #include     using namespace std; int main() {     int x = 5;     int &ref = x;     ref = 10;     int *ptr = &x;     *ptr += 5;     cout << x << " " << ref;     return 0; }

ref is declared as a reference to x, meaning ref is simply another name for the exact same memory location as x — it is not a separate copy. The statement ref = 10 therefore sets x to 10 directly. Next, ptr is a pointer holding the address of x, and *ptr += 5 dereferences ptr and adds 5 to whatever it points to — since ptr points to x, this updates x to 15. Because ref is an alias for x rather than an independent variable, printing ref afterward also reflects this same updated value, 15. The output is therefore '15 15'.