Understanding Pointers in C

What is a Pointer?

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

Basics

int x = 10;
int *p = &x;   // p holds the address of x

printf("%d", *p);  // 10  (dereference: value at address)
printf("%p", p);   // the actual address

Why Pointers Matter

• Pass large data to functions by reference (no copying).
• Dynamic memory allocation.
• Build linked lists, trees, and other structures.

Pointers and Functions

void increment(int *n) { (*n)++; }

int a = 5;
increment(&a);
printf("%d", a); // 6 — modified the original

Dynamic Memory

int *arr = malloc(5 * sizeof(int));
arr[0] = 100;
free(arr);  // always free what you malloc

FAQs

What is a null pointer?

A pointer set to NULL pointing to nothing. Always check before dereferencing. More in our C section.

What causes segmentation faults?

Accessing invalid memory — dereferencing NULL or freed pointers.