To gain experience with dde23, compute and plot the
solution of the following problem from . Solve
In this you will have to evaluate the history in a function and supply its name, say 'exer1h', as the history argument of dde23. Remember that both the ddefile and the history function must return column vectors. In  this problem is used to show how to prepare a class of DDEs for solution with DMRODE. You might find it interesting to compare this preparation to what you had to do.