What is a pointer?

It’s a representation of addresses which is an indicator that points to an address of a value.

Syntax:

 datatype*var_name ;  
 float*ptr  ;  // ptr point to address which holds float data 

Working of Pointer:

• Unary Operator (&) assigns the address of a variable to the pointer. This returns the address of the variable.
• Unary Operator(*) is used to access the value stored in the address which returns the value of the variable.

0x at the beginning shows the address in Hexadecimal form.

Code:

#include <bits/stdc++.h>

using namespace std;
int main() {

  int val = 433;

  int * ptr; // pointer variable

  ptr = & val; // assigning address of val to ptr

  cout << "Value of val : " << val << "\n";
  cout << "Value of pointer ptr and Address of val :  " << ptr << "\n";
  cout << "Value of *ptr : " << * ptr << "\n";
  return 0;
}

Difference between Reference and Pointers

Pointer: A pointer is a variable that holds the memory address of another variable.

• It can also be assigned to point a NULL value
• A pointer can be changed to point to any variable of the same data type.
• The pointer needs to be dereferenced with a *.

Reference: It is a variable that is referred to another name for an already existing variable. 

• Reference cannot be a NULL value
• Reference cannot be changed to refer to a variable object.

Array Name as Pointers

• The array name is used as a pointer to store elements in the array. 
• After that, we print the elements of the array using the same pointer. The compiler creates a pointer by default while we create an array.
• For example, if we have an array as arr, then arr[0] and & arr[0] both can be used.

Code:

#include<bits/stdc++.h>

using namespace std;

int main() {

  int arr[4] = {1,2,3,4};
    
  int * ptr;
  ptr = & arr[0];

  cout << "Values of Array\n";
  cout << ptr[0] << " " << ptr[1] << " " << ptr[2] << " " << ptr[3] << "\n";
  cout << "Address of each element of Array\n";
  cout << & ptr[0] << " " << & ptr[1] << " " << & ptr[2] << " " << & ptr[3] << "\n";
  return 0;
}

Pointer Arithmetic

• The following operations can be performed on the Pointers: Addition and Subtraction
• An integer can be added to a pointer
• An integer can be subtracted from a pointer
• The difference can also be taken from 2 pointers

Code:

#include <bits/stdc++.h>

using namespace std;
int main() {

  int arr[5] = {10,20,30,40,50};
 
  int * ptr;

  ptr = & arr[0];

  /*Traversing from left to right using addition */
  cout << "Left to Right\n";
  for (int i = 0; i < 5; i++) {
    cout << "Value of pointer ptr: " << ptr << "\n";
    cout << "Value of pointer *ptr: " << * ptr << "\n";

    ptr += 1;
  }
  cout << "\n\n";

  cout << "Right to Left\n";
  ptr = & arr[4];
  /*Traversing from right to left using addition */
  for (int i = 4; i >= 0; i--) {
    cout << "Value of pointer ptr: " << ptr << "\n";
    cout << "Value of pointer *ptr: " << * ptr << "\n";

    ptr -= 1;
  }

  return 0;
}

Special thanks to Shreyas Vishwakarma for contributing to this article on takeUforward. If you also wish to share your knowledge with the takeUforward fam, please check out this article