What is the difference between a cpp file and a h file

Question

Because I ve made  cpp files then transfered them into  h files  the only difference I can find is that you can t  include  cpp files   Is there any difference that I am missing

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A header   h   hpp       file contains   Class definitions   class X            Inline function definitions   inline int get cpus             Function declarations   void help      Object declarations   extern int debug enabled      A source file   c   cpp   cxx  contains   Function definitions   void help           or void X  f             Object definitions   int debug enabled   1      However  the convention that headers are named with a  h suffix and source files are named with a  cpp suffix is not really required  One can always tell a good compiler how to treat some file  irrespective of its file-name suffix   -x  lt file-type gt  for gcc  Like -x c        Source files will contain definitions that must be present only once in the whole program  So if you include a source file somewhere and then link the result of compilation of that file and then the one of the source file itself together  then of course you will get linker errors  because you have those definitions now appear twice  Once in the included source file  and then in the file that included it  That s why you had problems with including the  cpp file

User · Answer

I know the difference between a declaration and a definition    Whereas    A CPP file includes the definitions from any header which it includes  because CPP and header file together become a single  translation unit   A header file might be included by more than one CPP file The linker typically won t like anything defined in more than one CPP file   Therefore any definitions in a header file should be inline or static  Header files also contain declarations which are used by more than one CPP file   Definitions that are neither static nor inline are placed in CPP files  Also  any declarations that are only needed within one CPP file are often placed within that CPP file itself  nstead of in any  sharable  header file

User · Answer

h files  or header files  are used to list the publicly accessible instance variables and and methods in the class declaration   cpp files  or implementation files  are used to actually implement those methods and use those instance variables   The reason they are separate is because  h files aren t compiled into binary code while  cpp files are  Take a library  for example  Say you are the author and you don t want it to be open source  So you distribute the compiled binary library and the header files to your customers  That allows them to easily see all the information about your library s classes they can use without being able to see how you implemented those methods  They are more for the people using your code rather than the compiler  As was said before  it s the convention

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The  cpp file is the compilation unit   it s the real source code file that will be compiled  in C      The  h  header  files are files that will be virtually copy pasted in the  cpp files where the  include precompiler instruction appears  Once the headers code is inserted in the  cpp code  the compilation of the  cpp can start

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Others have already offered good explanations  but I thought I should clarify the differences between the various extensions      Source Files for C   c   Header Files for C   h    Source Files for C     cpp   Header Files for C     hpp   Of course  as it has already been pointed out  these are just conventions  The compiler doesn t actually pay any attention to them - it s purely for the benefit of the coder

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The C   build system  compiler  knows no difference  so it s all one of conventions   The convention is that  h files are declarations  and  cpp files are definitions   That s why  h files are  included -- we include the declarations

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A good rule of thumb is   h files should have declarations  potentially  used by multiple source files  but no code that gets run

User · Answer

By convention   h files are included by other files  and never compiled directly by themselves   cpp files are - again  by convention - the roots of the compilation process  they include  h files directly or indirectly  but generally not  cpp files

[c++] What is the difference between a .cpp file and a .h file?

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