Lesson 12·C Programming

Pointers in C

Direct memory addressing, dereferencing, and pointer variables

What is a Pointer?

A Pointer is a special variable that stores the direct memory address of another variable. In C, pointers are designated using the asterisk (*) symbol.

Pointers are derived data types that provide low-level access to memory, allowing efficient array manipulation, dynamic memory allocation, and pass-by-reference semantics.

Memory Address Illustration

Consider the declaration int *ptr; int tot = 95; ptr = &tot;

Memory address allocation diagram for pointers — Pointer variable storing the physical memory address of the integer variable tot.

Features & Capabilities of Pointers

A pointer variable must always be declared with the * prefix.
Pointers must point to matching data types (mixing types requires explicit casting).
Pointers provide the most efficient method for traversing and processing arrays and strings.
Enables functions to return multiple values or mutate caller data using addresses.
Essential for dynamic memory allocation using malloc(), calloc(), realloc(), and free().
Reduces program overhead and improves execution performance significantly.

Practical Pointer Example

Demonstrating the address-of operator (&) and dereference operator (*):

C Example

#include <stdio.h>

void main() {
    int a = 10;
    int *ptr;

    ptr = &a;  // ptr holds the memory address of variable a

    printf("Value of a: %d\n", a);
    printf("Value at *ptr: %d\n", *ptr);
    printf("Address stored in ptr: %p\n", (void*)ptr);
}

Program Output

Value of a: 10
Value at *ptr: 10
Address stored in ptr: 0x7ffd5b92e84c

Note

Using *ptr reads or modifies the value stored at the referenced memory address (dereferencing).