#import is identical to #include, except that it makes sure that the same file is never included more than once. It’s therefore preferred and is used in place of #include in code examples throughout Objective-C–based documentation.http://developer.apple.com/ mac/library/documentation/ cocoa/conceptual/ObjectiveC /Articles/ ocDefiningClasses.html
Search for “Header Search Paths” in Project Info, and add the path to your headers. (MacPorts headers live in
#includeis for System Header files.
#include "display.h"is for User Header files