  Numerical approximations to the solutions of three different problem classes
of singularly perturbed parabolic reaction-diffusion problems, each with a
discontinuity in the bound\-ary-initial data, are generated. For each problem
class, an analytical function associated with the discontinuity in the data, is
identified. Parameter-uniform numerical approximations to the difference
between the analytical function and the solution of the singularly perturbed
problem are generated using piecewise-uniform Shishkin meshes. Numerical
results are given to illustrate all the theoretical error bounds established in
the paper.
