A friendly Fortran DDE solver

DKLAG6 is a FORTRAN 77 code widely used to solve delay differential equations (DDEs). Like all the popular Fortran DDE solvers, new users find it formidable and in many respects, it is not easy to use. We have applied our experience writing DDE solvers in Matlab and the capabilities of Fortran 90 to the development of a friendly Fortran DDE solver. How we accomplished this may be of interest to others who would like to modernize legacy code. In the course of developing a completely new user interface, we have added significantly to the capabilities of DKLAG6.