Modifying Pointers in C++

In C++, pointers are variables that store the memory address of another variable. Modifying pointers involves changing what a pointer points to or the pointer's own address.

Key Concepts

• Pointer Basics:
  • A pointer is declared with an asterisk (*) before its name.
  • Example: int *ptr; declares a pointer ptr that can hold the address of an integer.
• Address-of Operator (&):
  • Used to get the address of a variable.
• Dereferencing Operator (*):
  • Used to access the value at the address stored in a pointer.

Example:

int value = *ptr; // value is now 10, which is the content of var

Example:

int var = 10;
int *ptr = &var; // ptr now holds the address of var

Modifying Pointers

Changing Pointer Values

• You can change the address a pointer is pointing to by assigning it a new address.

Example:

int var1 = 5;
int var2 = 15;
int *ptr = &var1; // ptr points to var1
ptr = &var2;      // ptr now points to var2

Pointer Arithmetic

• Pointers can be modified using arithmetic operations (like addition and subtraction).
• When you increment a pointer, it moves to the next memory location based on the type it points to.

Example:

int arr[] = {1, 2, 3};
int *ptr = arr; // points to the first element
ptr++;          // now points to the second element (arr[1])

Important Notes

• Dangling Pointer: A pointer that points to a memory location that has been freed/deallocated. Avoid using these pointers.

Null Pointer: A pointer that does not point to any address. It's good practice to initialize pointers to nullptr.

int *ptr = nullptr;

Conclusion

Understanding how to modify pointers is fundamental in C++. It allows for dynamic memory management and efficient data handling. Remember to use pointers responsibly to avoid common pitfalls like null and dangling pointers.