About the Runge Kutta algorithm
If you have solutions $x = [x_1,\dots, x_n]$ in a computer determined by their iterations where time is incremented $t_{n+1} = t_n + h$, then how do you extract the variable time?
For example suppose the solution to a system $S$ (we make $S$ to be a standard 1st year linear ODE with initial conditions) is a linear (or at least looks like it on a plot). How would you extract the actual points $(t_i, x_i)$? The $x_i$ can be extracted easily as that is the solution to the differential equation in a system $S$, but how can we extract $t_i$?