About header files

[Varahi]

How to create a new header file in c++ and how to input functions into it.
please tell this in a detailed manner.
i will be obliged to you.
Thank you!

[weaknessforcats]

Header files are just text files. They are called header files because they are usually included at the top (or head) of the source file.

/* mycode.c */
#include<afile>

The name of the header file is not important but usually a header file has a .h in C.

If you code this:

/* mycode.c */
#include"afile.h"

the header file must be in the same folder as mycode.c. If the header file is not there, then it must be in a "standard place".

If you code this:

/* mycode.c */
#include<afile.h>

the header file must be in a "standard place".

A "standard place" is a set of pre-defined paths you make. Your header file must be some where along one of those paths. How you define a "standard place" varies by compiler so you will need to read your compiler's documentation.

[divideby0]

I try to avoid cpp where I can, but I'll usually do something like

myheader.h

#ifndef __MYHEADER__
#define __MYHEADER__

// includes
#include <iostream>
#include <string>
#include <map>

// any user define types ie:
typedef std::map<std::string, std::string> tdm;

// any function prototypes
void foo(const std::string &);

#endif

main.cpp

#include "myheader.h"

int main() {

   foo("test");
   std::cin.get();
}

foo.cpp

#include "myheader.h"

void foo(const std::string &str) {
   std::cout << str << std::endl;
}

[weaknessforcats]

What do you mean by avoiding cpp files where you can?

[divideby0]

What do you mean by avoiding cpp files where you can?

I meant that I try avoiding the language where I can; I prefer using C becuase it's easier for a layman like myself to understand. :)

[weaknessforcats]

Thanks. I just wanted to be sure you were OK where header files are concerned.

[Banfa]

This #include<"afile .h"> would be a typo and should be #include"afile. h".

<pedantic>
Strictly all the standard says is that if you use the form #include<afile. h> the preprocessor searches for a sequence of implementation defined places.

If you use the form #include"afile. h" the preprocessor searches in an implementation defined manor and if that fails it treats it as if it had been #include"afile. h".

In every implementation I have seen this boils down to using the <> form searches down a list of paths (the included paths) given either as an environment variable or switches on the compiler command line (or a combination of both) and the "" form searches in the current directory and then down the same path.

What is not true is that if you use #include"afile. h" then afile.h must be in the same directory as afile.cpp/afile.c

Generally speaking in most of the projects I work on we use the "" form for any/all project header files and the <> form for standard library header files.
</pedantic>