14 Years
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Last Post by JCRARY

A header file is made up of pre-processor directives, classes, namespaces etc. a good place to look at is cplusplus.com. look at the classes, objects and namespaces chapters...


My God I even had a comp science teacher ask me this.Arrrg one will go mad.

It's simple.Cut a few funtions out of you code and paste them in a file with a .h extension and call #include "your_header_name.h" to include that.

Note: not < > but " " if it's in the current directory else you have to supply the full or relative path.

All the rules are same as normal C++ syntax.

That was very simple thing.Headers can be used for more things.They can just contain funtions declarations without definitions.In that case it will be used to link to a static library.

Eg.Make a header file with 2 funtion declarations like fun1(); fun2(); only
Include it with a cpp file and call the funtions and compile.

You will get no errors on compile but on linking you will see an error similar to the following:

undefined module fun1() refferenced from Module main.cpp
undefined module fun2() refferenced from Module main.cpp

I hope you understand a header in not really diffrent from a cpp file.Btw you can also include .cpp files.

Eg: #include "wow.cpp"


It is very very simple:

write some functions||define some macros||define structures/classes etc...
DO NOT include a main() function
save it with the name you want
e.g header.txt/cpp/in/out/...
you use it through: #include "..."
if you have variables in your header, do not redeclare them in your programs or it will give you an error "Multiple declaration for variable..."


Even if you include main() in a header and dont declare main() in any other funtion the program will complie and work properly.Headers are just a way to organise code.


well if you include main() in a header that would be more like a program than like a header but anyway you can ;)


did the computer science teacher ask you it on a test?

You bumped a 6-year-old thread for that????

Edited by Fbody: n/a


where can i find out a detailed information about How to write a header file ?

Trying to learn c++. The tutorial is missing a .h (header file) ?

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