Difference between Pointers and Reference in C++

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Pointers and Reference looks similar but there are some difference between both of them.

POINTER

  1. Its not necessary to initialize the pointer at the time of declaration. Like
    Code:
       
int a = 10;
int *P = &a; //It is not necessary
    Another way is :
    Code:
    int a  = 10;
int *P;
P =  &a;
  2. You can create the array of Pointer.
  3. You can assign NULL to the pointer like

    Code:
    int *P = NULL; //Valid
  4. You can use pointer to pointer.

REFERENCE

  1. Its necessary to initialize the Reference at the time of declaration. Like
    Code:
    int &a = 10;
int &a;   //Error here but not in case of Pointer.
  2. You can not create the Array of reference.
  3. You can not assign NULL to the reference like

    Code:
    int &a = NULL; //Error
  4. You can not use reference to reference.
leila likes this
Go4Expert Founder
27Jul2007,18:31   #2
shabbir's Avatar
Nice differences.
Go4Expert Member
27Jul2007,18:33   #3
Shishir191's Avatar
Thanks.
Go4Expert Member
14Aug2007,14:09   #4
kush_2207's Avatar
good one.....but what would you say if i write in .NET or even in JAVA
FileStream fs; // (or using any other class)
What is FileStream -> a pointer or a reference ?
Can you elaborate it for other platforms ?
Go4Expert Founder
14Aug2007,15:36   #5
shabbir's Avatar
In Java or C# everything is reference and there is nothing known as pointer.
Go4Expert Member
14Aug2007,18:54   #6
kush_2207's Avatar
Thank you sir.
Go4Expert Member
15Aug2007,09:14   #7
kaustubh's Avatar
Reference is the other name given to the same variable. Pointer is new variable created which can contain address of another variable.

Try an experiment

Code:
# include<iostream>
using namespace std;
int main()
{

int i = 90; // variable
int &j = i;  // reference 
int *P;   //  pointer
P =&i;

cout<<endl<< "address of variable :i" <<&i;

cout<< endl << "address of reference: j" <<&j;
cout<<endl<<"address of pointer : P"<<&P;
return 0;
}
OUTPUT:
 address of variable i: i0012FEDC
address of reference j: 0012FEDC
address of pointer p: 0012FEE0
so you see the address of i and reference j is same , address of pointer P is different.
Newbie Member
8Sep2007,13:37   #8
shal's Avatar
nice one
Newbie Member
10Sep2007,16:26   #9
zaka_d's Avatar
In C++ a reference variable is internally implemented as a constant pointer, and that is why it is necessary to initiallize a reference variable during declaration... as it is treated as a constant variable (pointer) internally.
Team Leader
10Sep2007,22:00   #10
DaWei's Avatar
That is incorrect, zaka. A reference is a second name (alias) for an object. You can't name something that doesn't exist, therefore you have to specify the object being aliased when you declare the reference. When a reference is passed as an argument, a copy of the objects address is passed. This is one fewer levels of indirection than when a pointer to the object is passed.
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