The Starlink HLP system is a set of subprograms and utilities which allows an application program to retrieve named items from a hierarchically-arranged library of text.
The facility is functionally very similar to the VAX/VMS Help system. The major differences are that the Starlink HLP system (i) is implemented in a portable way and is not tied to the VAX, and (ii) allows independent creation of multiple libraries which are bound together at run-time and appear to the user as a single ``tree''. The system is written in a free-standing manner and does not call any other Starlink packages.
The present document will be of most interest to application programmers, though users of application packages which incorporate the HLP system may find Section 2 of some value. Section 5 is relevant only to those providing software support for the package, or others who are interested in the internals of the system.