Header files must include a construction that prevents multiple inclusion.
The convention is an all uppercase construction of the file name with
_ seperator and the h suffix with __ before and after.
Example:
for file CoreBundle.h
#ifndef __CORE_BUNDLE_H__
#define __CORE_BUNDLE_H__
...
<code>
...
#endif //__CORE_BUNDLE_H__
Include statements must be located at the top of a file only.
