Pointers in C++ is a variable that holds the address of another variable in c++. The address is stored in the pointer variable and help in the implementation of call-by-reference.
Following pointers will be covered in this article,
- Pointers
- Pointers and Arrays
- Null Pointers
- Void Pointers
- Pointer Arithmetic Operation
- Pointer to Pointer
- Pointer to Functions
Starting off with this article on Pointers on C++
Syntax:
datatype *pointername; EXAMPLE: int *ptr;
- A pointer variable has a * sign before its name.
- A pointer is also called a locator or Indicator.
Uses Of Pointer:
- Dynamic Memory Allocation
- In Various Programs Of Arrays, Structure, And Functions
Here Is An Example Code:
#include <iostream>
using namespace std;
int main()
{
int num = 17;
int *ptr;
ptr = #
cout << "Value at ptr = " << ptr << "n";
cout << "Value at var = " << num << "n";
cout << "Value at *ptr = " << *ptr << "n";
}
Output:
Explanation:
In the above program, we show the basic working of a pointer. We have an integer variable num with value 17. We have pointer variable ptr of type int. We assign the address of num to the pointer ptr.
We first print the value of ptr, that is the address. Next, we print the num value and at the end, we print the value at the location held by the pointer ptr.
Moving on with this article on Pointers on C++
Pointers and Arrays:
We can consider the first element of an array as a pointer, as the array name contains the address of the first element. We can use a pointer in the following fashion.
Here is an example code:
#include <iostream>
using namespace std;
int main()
{
int arr[3] = { 5, 10, 20 };
int *ptr;
ptr = arr ;
cout << "Elements of the array are: ";
cout << ptr[0] << " " << ptr[1] << " " << ptr[2];
}
Output:
Explanation:
In the above program, we show the basic working of a pointer with an array. We have an array arr with values 5,10,20. We have pointer variable ptr of type int. We assign the address of arr to the pointer ptr.
We first print the value of ptr[0], that is the first element of the array. Next, we print the second and third elements respectively. As array elements are stored consecutively, so the pointer can access the other location of the array by incrementation.
Moving on with this article on Pointers on C++
Null Pointers:
There are the type of pointers that have no value and hold a null value
Example:
int *ptr=NULL;
They are very useful in data structures like a linked list.
Moving on with this article on Pointers on C++
Void Pointers:
These are the type of pointers that do not have a return type.
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Pointer Arithmetic Operation:
Different operations can be performed on pointers. Here are some important types.
- incremented (++)
- decremented ( — )
- difference between two pointers (p1-p2)
- addition of an integer to a pointer ( + or += )
- subtraction of an integer from a pointer ( – or -= )
Here is a code to demo some of these operations:
#include <iostream>
using namespace std;
int main()
{
int arr[3] = {10, 100, 200};
int *ptr;
ptr = arr;
for (int i = 0; i < 3; i++)
{
cout << "Value at different locations of array using *ptr = " << *ptr << "n";
ptr++;
}
}
Output:
Explanation:
We demonstrate simple arithmetic operation of incrementation of pointer variable is shown in the above program.
Moving on with this article on Pointers on C++
Pointer to Pointer:
In this type of system, there are two pointers. The first pointer points to the second pointer and the second pointer points to the variable that is holding the value.
Here is an Example Code:
</pre>
#include <iostream>
using namespace std;
int main () {
int num;
int *ptr;
int **pptr;
num = 3000;
ptr = #
pptr = &ptr;
cout << "Value of num :" << num<< endl;
cout << "Value available at *ptr :" << *ptr << endl;
cout << "Value available at **pptr :" << **pptr << endl;
return 0;
}
Output:
Moving on with this article on Pointers on C++
Pointer to Functions:
This is a way of passing pointers to functions. The function parameter must be declared as a pointer type. It is shown in the code below,
#include <iostream>
using namespace std;
float getAverage(int *arr, int size);
int main ()
{
int balance[5] = {1432, 232, 3232, 17, 502};
float avg;
avg = getAverage( balance, 5 ) ;
cout << "Average value is: " << avg << endl;
return 0;
}
float getAverage(int *arr, int size) {
int i, sum = 0;
double avg;
for (i = 0; i < size; ++i) {
sum += arr[i];
}
avg = double(sum) / size;
return avg;
}
Output
This is how we pass a pointer to a function.
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