HP aC++/HP C A.06.20 Programmer's Guide

Angle-bracketed include files are searched for in dir1, then dir2, followed by the
standard include directories.
aCC -Idir1 -Idir2 -c a.C
With view-pathing on, the following example searches for quoted include files in dir1
first and dir2 next, followed by the standard include directories, ignoring the directory
of a.C. Angle-bracketed includes are searched for in dir2 first, followed by the standard
include directories.
aCC -Idir1 -I- -Idir2 -c a.C
Header File Options 57