Pointers in C++

Pointers

• Pointers in C++ are special variables that store memory addresses of other variables. They are powerful but require careful use.
• Memory addresses uniquely identify each location in a computer's memory where a variable is stored.
• A pointer holds a memory address, not the variable's value itself.
• Declaring a pointer: int* ptr; // ptr is a pointer to an integer

Assigning Values to Pointers

• Use the & operator to get a variable's memory address: int x = 10; int* ptr = &x;
• ptr now holds the address of x.

Dereferencing a Pointer

• Use the * operator to access or modify the value at the address stored in the pointer: cout << *ptr; // Prints the value of x (10).
• *ptr = 20; // Changes the value of x to 20.

Null Pointer

• A pointer can be initialized to nullptr to indicate it doesn't point to a valid memory location: int* ptr = nullptr;

Void Pointers

• A void pointer can store the address of any data type.
• Its type is void*.

Double Pointers

• A double pointer holds the address of a pointer.
• Example: type** ptr;

Pointer Arithmetic

• Adding or subtracting integers to a pointer manipulates its memory address (e.g., pa = pa + 5). The size of the data being pointed to is a factor.
• A pointer can be compared to another using operators like ==, !=, >, <.

Pointers and Arrays

• The name of an array (without subscripts) is a pointer to the first element in the array: int arr[10]; int* ptr = arr;

Dynamic Memory Allocation

• Dynamically allocating memory lets you set aside memory at runtime.
• Use new to allocate memory (e.g., int* arr = new int[n];).
• Release memory when it is no longer needed using the delete[] operator: delete[] arr; to avoid memory leaks.

Array of Pointers

• An array can contain pointers as its elements.

Passing Arrays to Functions

• When an array is passed to a function, the function receives a pointer to the first element of the array. This allows changes to the array to be reflected in the calling function.

References and Pointers

• Call-by-value methods copy the variable's value, call-by-reference methods pass the variable's address.
• Pass-by-reference with a pointer, or reference, permits changing the original variable within the function.

String Pointers

• String variables have memory locations.
• The address can be found using the & operator.