A review on singular perturbed delay differential equations

In this paper, existing available literature on numerical solution of singularly perturbed and singular perturbed delay differential equations is reviewed. These equations arises in mathematical modeling of variational problems in control theory,physical and biological phenomena like optically bistable devices, description of human pupil reflex and a variety of models for physiological processes or diseases. The purpose of this work is to investigate the classof singular type problems that are solved till now using different numerical methods. The objective is to motivate the researchers to develop new methods for calculating efficient solution of such problems.There is a lot of work reported in literature to solve these typesof equations both numerically and analytically. This paper limits its coverage to the work done by numerous researchers between 2002 and 2017.