There are two ways of loading programs into Prolog -- compiling source files and loading pre-compiled QOF files. Earlier releases of Prolog distinguished between compiling and consulting source files. Consulting a file caused the code to be loaded in an interpreted mode so that it could be debugged. Now compiled code is fully debuggable, so there is no longer any need to distinguish between compiling and consulting, and the built-in predicate consult/1 is now just a synonym for compile/1. Interpretation is now only used for the execution of dynamic code.

This section contains references to the use of the module system. These can be ignored if the module system is not being used (see ref-mod for information on the module system).