Lesson 34: Pointers Part 1: What are Pointers?

Pointers are the most powerful and unique feature of C. A pointer is a variable that stores the memory address of another variable.

Memory and Addresses

Every byte in computer memory has a unique address (a number) assigned to it. When we declare a variable, memory is allocated, and the compiler knows its address.

Pointer Declaration

To declare a pointer variable, use the dereference operator (*).

Syntax: data_type *pointer_variable_name;

The data_type specifies the type of data the pointer points to, not the type of the pointer itself (which always holds an address).

c int *ptr_to_int; // Pointer to an integer char *ptr_to_char; // Pointer to a character (or string) double *ptr_to_double; // Pointer to a double

Operators for Pointers

1. Address-of Operator (&)

Returns the memory address of a variable.

2. Dereference/Indirection Operator (*)

Accesses the value stored at the memory address held by the pointer.

c int x = 100; int *p;

// 1. Assign the address of x to p p = &x;

// 2. Access the value at the address stored in p printf("Value of x: %d\n", *p); // Output: 100

// Change the value of x using the pointer *p = 200; printf("New value of x: %d\n", x); // Output: 200