Message-Id: <199910201103.OAA00495@ankara.Foo.COM>
From: "S. M. Halloran" <mitch AT duzen DOT com DOT tr>
Organization: User RFC 822- and 1123-compliant
To: djgpp AT delorie DOT com
Date: Wed, 20 Oct 1999 15:10:28 +0200
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Subject: Re: help with .h files
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Section 4.3 (Chap. 4) of _The C++ Programming Language_ (2nd Ed.) by Bjarne 
Stroustrup explains what header files are to be used for, and this applies in 
standard C as well as C++ to a great extent.

Pp. 113-4 say the following:

A header file may contain:
                                          Example
   --------------------------        --------------------------
1.  type definitions                 struct point { int x, y; }
2.  templates                        template<class T>
                                            class V { /* ... */ }
3.  function declarations            int strlen(const char *);
4.  inline function definitions      inline char get() { return *p++; }
5.  data declarations                extern int a;
6.  constant definitions             const float pi=3.141593;
7.  enumerations                     enum bool { false, true };
8.  name declarations                class Matrix;
9.  include directives               #include <signal.h>
10. macro definitions                #define Case break;case
11. comments                         /* a comment */

Headers should never contain:

1.  ordinary function definitions    char get() { return *p++; }
2.  data definitions                 int a;
3.  constant array definitions       const tbl[] = { /* .... */ };

One thing that is only really barely touched upon is whether to use a single 
header file for multiple sources, or supply one header file for each source, or 
to use a combination.

On 20 Oct 99, James Vasile was found to have commented thusly:

> Header files are places to define structures and macros, for the most
> part. They get included (#include "header.h") at the top of the .cpp
> files that include the actual code you're writing. At least, this is
> how it is in c.  I've not done much cpp, and perhaps .h files have
> functions in cpp that they don't have in c.
> 
> Peace,
> -J
> 
> 
> On Thu, 22 Jul 1999 17:09:35 GMT, manfred DOT heumann AT uni-bielefeld DOT de
> (Manni Heumann) wrote:
> 
> >In article <37CECA25 AT MailAndNews DOT com>, "Psycho_Circus" <overtkill AT MailAndNews DOT com> wrote:
> >>Is there any help or documentation on the .h files that come with the djgpp 
> >>c++ compiler?  I'm new to c++ and do not understand exactly what the .h 
> >>files 
> >>do.  For example, I never would have figures out what cout or cin is w/o the 
> >>c++ book I got.  How do I know what functions are in the .h files and what 
> >>they do?  Thanks in advance for any help.
> >>
> >>- Me
> >>
> >
> >Keep on reading! Don't stop after the first chapter.



Mitch Halloran
Research (Bio)chemist
Duzen Laboratories Group
Ankara       TURKEY