More About Header Files

• They are used to store information common to multiple source files
• Source files can use the information by #includeing the header file
• The use of header files reduces duplication and allows for easier modification because a constant or type declaration need only be changed in one place
• Header files should only contain:
  • Definitions of constants
  • Type declarations (typedefs)
  • Macro definitions
  • Extern declarations
  • Function declarations (prototypes)
  • struct and class definitions
  
  
• Header files should not contain:
  • Any executable code i.e., no function definitions
  • Definitions of variables. Otherwise the inclusion of the header file in multiple source files will cause a multiple definition linkage error