Pointer in C++
Pointer in C++
Pointer in C++ is a variable that stores the memory address of another variable. Pointers allow you to indirectly access and manipulate the values of other variables by referring to their memory addresses.
To declare a pointer in C++, you can use the following syntax:
data_type* pointer_name;
Here, data_type is the data type of the variable that the pointer will point to, and pointer_name is the name of the pointer.
For example, to declare a pointer that points to an integer variable, you can use the following code:
int* my_pointer;
To assign a value to a pointer, you can use the address-of operator (&) to obtain the memory address of a variable, like this:
int x =5;
my_pointer= &x; // assign the memory address of x to the pointer
To access the value of the variable that a pointer points to, you can use the dereference operator (*) to obtain the value stored at that memory address, like this:
int y =*my_pointer; // get the value of the variable that the pointer points to
You can also use pointers for dynamic memory allocation, which allows you to allocate memory at run-time instead of compile-time. The new operator can be used to allocate memory on the heap, and the delete operator can be used to deallocate that memory when it is no longer needed.
For example, to allocate memory for an integer on the heap, you can use the following code:
int* my_pointer = new int;
To deallocate the memory when it is no longer needed, you can use the following code:
delete my_pointer;
It’s important to note that using pointers requires careful memory management to avoid memory leaks and other errors. It’s also important to ensure that pointers are pointing to valid memory addresses before dereferencing them, to avoid segmentation faults and other runtime errors.
Type of Pointers:
There are four types of pointers:
Null Pointer: A null pointer is a pointer that does not point to any memory location. It is represented by the constant nullptr in C++.
Void Pointer: A void pointer is a pointer that has no data type associated with it. It can be used to point to any type of data, but cannot be directly dereferenced. To dereference a void pointer, it must be explicitly cast to another pointer type.
Pointer to Object: A pointer to an object is a pointer that points to an instance of a class or struct.
Pointer to Function: A pointer to a function is a pointer that points to a function in memory. It can be used to call the function indirectly, or to pass the function as an argument to another function.
Here is an example of how to declare each of these pointer types in C++:
// Null Pointer
int* ptr1 = nullptr;
// Void Pointer
void* ptr2 = nullptr;
//Pointer to Object
class MyClass {
public:
void myMethod() {
cout << "Hello from MyClass!" << endl;
}
};
MyClass* ptr3 = nullptr;
//Pointer to Function
void myFunction(int x) {
cout << "The value of x is: "<< x << endl;
}
void(*ptr4)(int) = &myFunction;
In the example above, ptr1 is a null pointer to an int, ptr2 is a void pointer, ptr3 is a pointer to an instance of the MyClass class, and ptr4 is a pointer to the myFunction function.