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what is the difference between #include <filename> and #include “filename”
Difference between writing #import and #import "filename.h" i.e written the file name in angular brackets and quotes?
Quoted form This form instructs the preprocessor to look for include files in the same directory of the file that contains the #include statement, and then in the directories of any files that include (#include) that file. The preprocessor then searches along the path specified by the /I compiler option, then along paths specified by the INCLUDE environment variable.
Angle-bracket form This form instructs the preprocessor to search for include files first along the path specified by the /I compiler option, then, when compiling from the command line, along the path specified by the INCLUDE environment variable.
Source http://msdn.microsoft.com
来源：https://stackoverflow.com/questions/3156432/difference-between-writing-import-filename-h-and-import-filename-h-i-e-wri