On some architectures, SWI-Prolog allows for the creation of saved states. Currently, the C-sources define two alternative implementations for them. The old implementation (6) creates an entirely self-contained executable. It supports only the save_program/[1,2] predicates. The new implementation (7) creates a file that is read by the `base' program. This file contains the data-area of the SWI-Prolog process and optionally the Prolog- and C stacks. This implementation supports save_program/[1,2], save/[1,2] and restore/1. The state-file depends entirely on exactly the Unix program-file used to create it.