object and pointer declarations

[amitk3553]

Like we have class:
class ABC
{};

Then what is difference b/w two following declarations:

ABC abc; and ABC *abc;

Where are use cases of these object and pointer declarations?

[MikeyBoy]

See my post in this thread:

http://cplusplus.com/forum/general/105593/

for some reasons to use pointers.

[amitk3553]

What is the meaning of pass by reference??

[SirSmilesaLot]

in java its simple everything is a reference, in c++
abc is an object, * abc is reference capable of pointing to any object of same type.
so if u say

ABC abc;
ABC *bca=abc; // just acts as a reference to abc object
ABC cda=abc; // creates a new object copying the contents of abc object 

[MikeyBoy]

http://lmgtfy.com/?q=C%2B%2B+pass+by+reference

[MikeyBoy]

abc is an object, * abc is reference capable of pointing to any object of same type.

No. It's a pointer. In C++, a reference is different from a pointer.

Please don't confuse people by giving them misleading information.

[SirSmilesaLot]

Ok my mistake, here u go amit

ABC &bca=abc;// is a reference
ABC *bca=abc;// is a pointer 

only difference is reference cannot be null and once assigned it cannot be re-assigned.A pointer can be null, and can be made to point to different variables.However internally compilers implement references using pointers.

[MikeyBoy]

only difference is reference cannot be null and once assigned it cannot be re-assigned.A pointer can be null, and can be made to point to different variables.

No, that's not the only difference. The syntax for using a reference is different from the syntax for using a pointer. References have no equivalent of pointer arithmetic.

Please don't confuse people by giving them misleading information.

[SirSmilesaLot]

Milky Buoy, please give a detailed explanation so that itllb convenient for amit , i suppose u do something more than chiiping into others answers :D

[z05DSL3A]

anirudh sn wrote:

Milky Buoy, please give a detailed explanation so that itllb convenient for amit , i suppose u do something more than chiiping into others answers :D

just because someone pulls you up on your inaccuracy doesn't mean you have the right to bait him.

[Rechard3]

ABC* ptr; create a pointer that can point to any object of type ABC.

a pointer is no more than a 4byte variable (on 32bit platforms), it is NOT a complete object of that class.
the task of a pointer is to hold the memory address of some object.
in this case you say that the pointer POINTS to that object.
you can use the referencing operator "&"to get the address of any object (even the address of a pointer), use it like this:
ptr = & object;

you can use the de-referencing operator "*" to get the object pointed to by your pointer:

ABC object_2;
object_2 = (*ptr);

ABC object; creates a full instance of the class ABC

[MikeyBoy]

Milky Buoy, please give a detailed explanation so that itllb convenient for amit

There's absolutely no point me spending time re-typing information that is already readily available out there online. I'm happy to help with problem-solving, and to help identify and fix problems with people's code, as my posting history here shows. But if information is easily found elsewhere, I don't see the purpose in retyping it.

It would have been trivial for Amitk to type a Google search - or consult his/her textbook - to find the information they were looking for in seconds.