Most Prolog systems will implement other built-in predicates for formatted input and output, for handling windows, and so on. In addition, most Prologs can now call procedures written in C and other languages, giving you access to their input and output (as well as to other libraries such as NAG).
Prolog also has built-in predicates for reading files of clauses into the database, and for adding or deleting clauses as the program runs.