Pointers in C — Complete Guide

Pointers are one of the most powerful and fundamental features in the C programming language. If you truly understand pointers, you unlock low-level memory control, efficient data structures, and system-level programming. 1. What is a Pointer? A pointer is a variable that stores the memory address of another variable. int a = 10 ; int * p = & a ; Memory Diagram Stack Memory: +------------+ +------------+ | a = 10 | 0x100 | p = 0x100 | 0x200 +------------+ +------------+ p ───────────────► a Debug Scenario ❌ Bug: printing pointer incorrectly printf ( "%d" , p ); // WRONG ✅ Fix: printf ( "%p" , ( void * ) p ); 2. Pointer Declaration data_type * pointer_name ; Memory Insight The pointer size is fixed (typically 4 or 8 bytes), regardless of type. int * p ; // 8 bytes (on 64-bit system) char * c ; // 8 bytes Debug Scenario ❌ Misinterpretation bug char * p ; int x = 1000 ; p = ( char * ) & x ; printf ( "%d" , * p ); // unexpected value 3. Address Operator (&) int x = 5 ; printf ( "%p" , & x