This document discusses dynamic memory allocation in C using four main functions: malloc(), calloc(), realloc(), and free(). It provides examples of using each function and explains their differences. malloc() allocates memory during execution but does not initialize it, while calloc() initializes the memory to zero. realloc() modifies the size of previously allocated memory. free() frees up memory allocated by the other functions. The document aims to help understand these important functions for dynamic memory management in C.