Sometimes the boundary conditions in the problems are so complex and there is no way to introduce them in GUI interface of ABAQUS software. For example, ABAQUS features can be sufficient for location-dependent or time-dependent boundary conditions separately. If these two dependencies are not separable, the use of DISP or VDISP subroutine is necessary.
The DISP and VDISP Subroutines Training package discusses the details of these two Subroutines and discusses the basic principles and concepts for writing these Subroutines along with examples.
You can watch demo here.