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The best exmaple I could give if B is car then A is a fleet of cars with all the options
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In that case, your second example (which is neither derived or multiple base classes).
'A' has a fleet (array) of cars but it is not a car.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/coffee.gif)
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okay thankx its hard to get into OO thinking
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If it helps any:
"Is ..." Use inheritance
"Has ..." Add a member
Example:
given a base class fruit
class apple - apple "is" a fruit so derive apple from fruit
class fruitbasket - a fruit basket "has" fruit so add fruit (or an array of fruit) as a member of the fruitbasket class
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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I think I was looking at the other way ....a base has lets say 3 data members/methods....
If I want to use those but I need another method/dats member
I will dervie the base and in the inherted class and add to it
I think what you are saying it works the other way around
the base has 10 data members/methods The drevid class only uses 7 data members/methods
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Data members/methods and the amount of data members/methods isn't relevant to the class hierarchy.
Those are only relevant to the class they're members of.
Mark Salsbery
Microsoft MVP - Visual C++
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I'll put another way I thought of the concept derived class(s) as a dervived class uses the base class .. but adds functionality
Or Is it just the opposite way of thinking a base has all the functionality but derived class just picks the one it needs
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ForNow wrote: a dervived class uses the base class .. but adds functionality
A derived class IS the base class. The derived class can alter and/or add to the functionality
of its base class.
Again, the class hierarchy shouldn't be designed around the members. The members are whatever is
necessary to implement the functionality of a class.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://codeproject.freetls.fastly.net/script/Forums/Images/coffee.gif)
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I understand I am going say something to see if I undertand what you mean a typical way of altering functionality would be to declare a method as Virtual that way the derived class can implement Its version of the method
Or Since dervied members can have thier version of the Base('s) constructer that would be a way of altering the functionality
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ForNow wrote: a typical way of altering functionality would be to declare a method as Virtual that way the derived class can implement Its version of the method
Yes. That's polymorphism (through inheritance)
ForNow wrote: Since dervied members can have thier version of the Base('s) constructer that would be a way of altering the functionality
Yes. Derived class constructors can also both alter and extend the base class constructor
implementation, but it's not quite the same as overriding a virtual function. There's
nothing virtual about constructors.
Mark Salsbery
Microsoft MVP - Visual C++
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Thankx I think I am ready to code.... After being a Dinasour Assembler programmer for 30 years writting procedurel code its hard to change my way thinking
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Have fun! I coded a few years in assembler and C before C++, but not 30 
Thinking in terms of classes will be second-nature in no time.
Cheers,
MArk
Mark Salsbery
Microsoft MVP - Visual C++
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Puncuation of some sort would extremely help in getting your ideas across.
Though I speak with the tongues of men and of angels, and have not money, I am become as a sounding brass, or a tinkling cymbal.
George Orwell, "Keep the Aspidistra Flying", Opening words
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can i add a quetion on the end?
i have a base class animalClass.hpp i have a derived Dog class and main in dogObj.cpp and a derived Cat class in catObj.cpp what i wanted to know is should i have animalClass.hpp dogClass.hpp, catClass.hpp, declaring the classes and have a seperate animalObj.cpp for main() to constrol the functions etc? at the moment my animalClass is about fifty lines as are the other animal classes, with my main () about 80 lines
thanks in advance
paul
if ignorance is bliss then knock the smile off my face!!!
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1slipperyfish wrote: should i have animalClass.hpp dogClass.hpp, catClass.hpp, declaring the classes and have a seperate animalObj.cpp
you need header files (.h, .hpp) if you want to use the classes in other .cpp files so they can be #include < ...>
If the class is defined in a cpp file the visibility of it is limited to (not sure) that file maybe.
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thanks for the reply led mike 
i have rewritten my classes into baseClass.hpp, CatClass.hpp, and DogClass.hpp with farms.cpp initialising the functions and having main()
i had a lot of trouble compiling as it kept saying i had already declared my Mammal class in baseClass however if you add [code]#ifndef BASE_CLASS_HPP
#define BASE_CLASS_HPP[/code] at the top of baseClass.hpp and [code]#endif[/code] at the bottom it works.
you all probably already new that but i've just wasted 2 1/2 hours of my life learning that the hard way
thanks again
paul
if ignorance is bliss then knock the smile off my face!!!
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MAybe I shouldn't answer this after all I work as a MainFrame Assembler Dino programmer
I think think if you declare it in the code/obj/cpp you just have to qualify the method with Class name e.g. DogClass :: dogmethod saying that this dogmethod is releated to the dogalass Class
Trying to get into the future.....
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thanks
paul
if ignorance is bliss then knock the smile off my face!!!
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Hi there. I'm pretty new to coding, I'm trying to (slowly but surely) design a program to receive data from a dyno that I'm fabricating. I'm guessing I'd best use the serial port, from what I read using USB 2.0 is pretty much harder. I'd be putting together a microsystem using either a microprocessor or my own electronics. I'd have to transmit data like engine rpm, air/fuel ratio, dyno drum speed etc. Is there a way to read analogue signals with a pc or can it only use digital signals?
If anyone has some good links or books on communicating with the outside world using a pc, I'd love to have some. Thanks a bunch!
Brian
Yup, I'm a NEWB
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You may want to post this on the hardware board[^].
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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Alrighty, thanks for the quick reply!
Brian
Yup, I'm a NEWB
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We are using the February 2006 version of DirectX. When we insert the following line:
#define new DEBUG_NEW
we get the following errors from the Directx Modules:
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.h(392)
: error C2059: syntax error : 'string'
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.h(392)
: error C2091: function returns function
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.h(392)
: error C2802: static member 'operator new' has no formal parameters
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.h(393)
: error C2059: syntax error : 'string'
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.h(393)
: error C2090: function returns array
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.inl(987
) : error C2761: 'void *(__cdecl *_D3DXMATRIXA16::operator new(void))(size_t)' :
member function redeclaration not allowed
c:\program files\microsoft directx sdk (february 2006)\include\d3dx9math.inl(987
) : fatal error C1903: unable to recover from previous error(s); stopping compil
ation
How can we take advantage of the DEBUG_NEW capability and also get around these errors?
BRC
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Defining DEBUG_NEW after any included header files has always worked for me.
Mark
Mark Salsbery
Microsoft MVP - Visual C++
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