dev-cpp-users

[Dev-C++] Header Files

[<ric...@ya...>]

Hi.

I'd be grateful if someone could write a few lines to
help me understand header files.

I know that #include is used to read source code from
a file into the current file, and that MyClass.h holds
the declaration of a class whereas MyClass.cpp holds
the definition of the class. The MyClass.cpp file has
a #include "MyClass.h" so that it reads in the class
declaration.

I'm a bit confused as to why, in any examples I see, a
main.cpp file uses #include "MyClass.h": shouldn't the
main.cpp file require both the class declaration and
its definition?

Many thanks.

Richard

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RE: [Dev-C++] Header Files

[Ioannis V. <no...@ya...>]

In the case of a class there is no reason to have 2 files, since it can only
defined once (in one file, or manually many times in separate files but
using exactly the same definition-a habbit leading to troubles. Only
#includes of the definition is the right way). So my guess is that in the
implementation file he #includes the .h file (or the opposite).



Ioannis

* Ioannis Vranos
* Programming pages: http://members.nbci.com/noicys
* Alternative URL: http://run.to/noicys


> -----Original Message-----
> From: dev...@li...
> [mailto:dev...@li...]On Behalf Of
> Richard Southworth
> Sent: Monday, April 09, 2001 10:09 AM
> To: dev...@li...
> Subject: [Dev-C++] Header Files
>
>
> Hi.
>
> I'd be grateful if someone could write a few lines to
> help me understand header files.
>
> I know that #include is used to read source code from
> a file into the current file, and that MyClass.h holds
> the declaration of a class whereas MyClass.cpp holds
> the definition of the class. The MyClass.cpp file has
> a #include "MyClass.h" so that it reads in the class
> declaration.
>
> I'm a bit confused as to why, in any examples I see, a
> main.cpp file uses #include "MyClass.h": shouldn't the
> main.cpp file require both the class declaration and
> its definition?
>
> Many thanks.
>
> Richard
>
> ____________________________________________________________
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>

Re: [Dev-C++] Header Files

[<csc...@gm...>]

Hallo Richard,

>
> I'm a bit confused as to why, in any examples I see, a
> main.cpp file uses #include "MyClass.h": shouldn't the
> main.cpp file require both the class declaration and
> its definition?
>

the compiler needs to know the class declaration to generate a function
call. If you call a function (don't matters if it is in a class or not), the
compiler needs to know how many arguments from which type in which order
must be pushed onto the stack before the call. The compiler will generate
code that does this. Then the compiler will generate the code actually does
the call. Finally, the compiler must know the return type from the function
in order to generate code that pops it off the stack. The compiler doesn't
need to know the function definition to generate a function call.

chris