The ARCHI manual  provides a sample program for
on [0,4] with history y1(t) = cos(t),y2(t) = sin(t) for t < 0 and initial values y1(0) = 0,y2(0) = 0 . Notice that y1(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 .
C.A.H. Paul, A user-guide to Archi, Numer. Anal. Rept. No. 283,
Maths. Dept., Univ. of Manchester, U.K., 1995.