The ARCHI manual [17] provides a sample program for
solving

y_{1}¢(t)

=

y_{1}(t-1) y_{2}(t-2)

y_{2}¢(t)

=

-y_{1}(t) y_{2}(t-2)

on [0,4] with history y_{1}(t) = cos(t),y_{2}(t) = sin(t) for t < 0 and initial values y_{1}(0) = 0,y_{2}(0) = 0 . Notice that y_{1}(t) is discontinuous at the initial
point. For practice, compute and plot the solution. The sample
program specifies a pure absolute error of 10^{-9}.
dde23 does not permit a pure absolute error, but for
practice with options, use the default relative error tolerance
and set 'AbsTol' to 1e-9. You might find it
interesting to compare your program to the sample in [17].