# I need help with quadrotor_propulsion.cpp code

Here's the code, I am trying to understand it, but I don't understand any of these variables, for example:

boost::array<real_T,4>  x;
boost::array<real_T,4>  x_pred;
boost::array<real_T,10> u;  (line 79, why do we have 10 here ?)
boost::array<real_T,14> y; (line 80 of the code, why do we have 14 here) ?