Dereferencing a Pointer in C++
In C++, dereferencing a pointer means accessing or altering the value kept in memory at that address pointed to by a pointer. This can be done by using the * operator(asterisk) to get the value of the particular variable from its address.
Steps for Creating Dereferencing a Pointer in C++
These steps must be followed for creating a dereferencing a pointer in C++ and modify its value:
1. Create a pointer variable, initialize it with the address of the variable whose value you want to update, and then declare the variable.
int* ptr = &x;
int x = 20;
2. To access the value stored at the memory address the pointer points to, dereference the pointer using the asterisk (*) operator.
ptr * value = int;
3. Change the result of dereferencing the pointer.
value = 10;
4. Dereferencing the pointer on the left side of an assignment will return the updated value to the memory address.
Value = *ptr;
The variable that the pointer was pointing to has now changed in value.
Note: The * symbol can be confusing in this situation since it performs two distinct functions in our code. When used in the declaration (string* ptr), it produces a pointer variable. It functions as a dereference operator when not utilized in a declaration.
Example:
#include<iostream>
using namespace std;
int main() {
int x = 20; // Declare an integer variable
int* ptr = &x; //Referencing
int value = *ptr; // Dereferencing
cout<< value;
return 0;
}
Output
![Dereferencing a Pointer in C++](https://static.tutorialandexample.com/cpp/dereferencing-a-pointer-in-cpp1.png)
Explanation: In the above example, we declare an integer variable x and initialize it with the value 20. Then, we declare a pointer ptr and assign the address of x to it using the address-of operator (&). Finally, we dereference the pointer using the asterisk operator * and assign the value to the variable value. The x(20) value is accessed and stored in a value, then printed to the terminal.
Uses of Dereferencing a pointer in C++
In C++, dereferencing pointers is crucial for some reasons and has a variety of applications. Here are some typical C++ applications for dereferencing pointers:
1) Pointers let you quickly access and edit data kept in a particular location in memory. Dereferencing a pointer allows you to access or alter the information in that memory location.
2) Pointers are frequently used in dynamic memory allocation, such as when new is used to allocate memory for objects or arrays at runtime. After allocating memory, you can access and modify the dynamically allocated memory by dereferencing the pointer.
3) Pointers can be increased or decreased to move between linked data structures or arrays. The element pointed to by the modified pointer can be accessed by dereferencing a pointer after incrementing or decrementing it.
4) Function argument passing: Function arguments are frequently passed by reference using pointers. The value at the memory address supplied as an argument can be directly modified by dereferencing the pointer inside the function.
5) Functions that return values can return pointers, allowing you to return the locations of locally allocated memory or variables. The value that the function returned can be accessed by dereferencing the returned pointer.
6) When working with complex data structures like linked lists, trees, or graphs, dereferencing Pointers is essential. It allows you to move through and interact with the nodes or components of these structures.
7) A function's address is stored in a function pointer. You can call and run a function code by dereferencing a function pointer.
These are only a few instances of how C++ uses dereferencing references. Pointers enable more complex programming techniques and increase memory management flexibility and efficiency. Pointers should be handled carefully to prevent risks like memory leaks and null pointer dereferences.
Dereferencing with complex datatypes
1) With arrays
In C++, dereferencing pointers with arrays enables access to and modification of the array's elements. Pointer dereferencing can be used to manipulate array elements because when supplied to functions or assigned to pointers, arrays degrade into pointers.
Here's an example demonstrating dereferencing pointers with arrays:
#include <iostream>
using namespace std;
int main() {
int arr[] = {1, 2, 3, 4, 5};
int* ptr = arr; // Assigning the array to a pointer
// Dereferencing the pointer to access and modify array elements
for (int i = 0; i < 5; i++) {
cout << "Element at index " << i << ": " << *(ptr + i) ;
}
// Modifying array elements using dereferenced pointer
*(ptr + 2) = 10; // Change the value at index 2
// Printing the modified array
cout << "Modified array: ";
for (int i = 0; i < 5; i++) {
cout << arr[i] << " ";
}
cout << endl;
return 0;
}
Output
![Dereferencing a Pointer in C++](https://static.tutorialandexample.com/cpp/dereferencing-a-pointer-in-cpp2.png)
We declare an integer array called arr with five elements in the example above. Next, we use the array name to assign the array to a pointer ptr. Since pointers are what remain when an array decays, ptr now points to the array's first element.
The asterisk operator * allows us to access the individual array elements by dereferencing the pointer ptr. Pointer arithmetic (ptr + i) is used in the for loop to traverse over the array and dereference it to access the element at each index.
When changing an element in an array, we access the element at index 2 using the dereferenced pointer (ptr + 2) and assign a new value (10 in this case).
2) With strings
In C++, dereferencing pointers with strings enables you to access and modify a string's characters. Since strings are character arrays in C++, you can manipulate the string's characters using pointer dereferencing.
Here's an illustration showing how to dereference points using strings:
#include <iostream>
Using namespace std;
int main() {
char str[] = "Hello, World!";
char* ptr = str; // Assigning the string to a pointer
// Dereferencing the pointer to access and modify characters
while (*ptr != '\0') {
cout << *ptr;
ptr++;
}
cout << endl;
return 0;
}
![Dereferencing a Pointer in C++](https://static.tutorialandexample.com/cpp/dereferencing-a-pointer-in-cpp3.png)
Explantation : In this example, the text "Hello, World!" initializes the character array "str." The array name is then used to assign the array to a pointer, or "ptr." Right now, the pointer is pointing at the string's initial character. We can access the string's characters by dereferencing the pointer ptr with the asterisk operator *. We cycle over the string in the while loop by incrementing the pointer ptr and dereferencing it until the null character '0,' which denotes the end of the string. We got output each character using cout<< *ptr; inside the loop.