cout < < showpoint < < 123.0

This code will print out the number 123.000, with the decimal point and trailing zeros included, using the "showpoint" manipulator in C++.

Here's an example of how it might be used in a complete program:

#include <iostream>
using namespace std;

int main() {
  cout << showpoint << 123.0 << endl;
  return 0;
}

Output:

123.000