How to Dereference a Pointer

In computer programming, pointers are used to store memory addresses as values. However, sometimes, we need to access the actual value stored at that memory address. This process of accessing the value at the memory address stored in a pointer is called dereferencing a pointer. In this article, we will explore how to dereference a pointer in various programming languages.

What is Dereferencing a Pointer?

Dereferencing a pointer means accessing the value stored at the memory address stored in the pointer. In other words, it means “following” the pointer to the actual memory location and retrieving the value stored there.

C Programming Language

In C, dereferencing a pointer is done using the unary asterisk operator (*). For example:

int* ptr = &x;  // ptr is a pointer to an integer
int value = *ptr;  // dereference the pointer and assign the value to value

In this example, ptr is a pointer to an integer, and &x returns the memory address of the variable x. The unary asterisk operator * is used to dereference the pointer, effectively retrieving the value stored at the memory address stored in ptr.

C++ Programming Language

In C++, dereferencing a pointer is similar to C. However, C++ provides more syntax sugar for pointer manipulation. For example:

int* ptr = &x;  // ptr is a pointer to an integer
int value = *ptr;  // dereference the pointer and assign the value to value

Additionally, C++ provides the arrow operator (->) to access members of a struct or class through a pointer. For example:

struct Person {
    int age;
};

Person* person = new Person();
person->age = 30;  // access the age member through the pointer

Java Programming Language

In Java, dereferencing a pointer is not necessary, as Java is a garbage-collected language and does not allow direct memory manipulation. However, Java provides the new keyword to create objects, and the dot operator (.) to access object members. For example:

Person person = new Person();
person.age = 30;  // access the age member through the object reference

Python Programming Language

In Python, dereferencing a pointer is not necessary, as Python is a high-level language and does not provide direct access to memory. However, Python provides the id() function to get the memory address of an object, and the sys.getsizeof() function to get the size of an object. For example:

person = Person()
print(hash(person))  # get the memory address of the object
print(sys.getsizeof(person))  # get the size of the object

Conclusion

Dereferencing a pointer is a fundamental concept in programming, allowing us to access the value stored at a memory address. In this article, we explored how to dereference a pointer in various programming languages, including C, C++, Java, and Python. Understanding how to dereference a pointer is essential for effective programming and is a crucial skill for any programmer.