Memory leaks are the biggest overhead for a programmer. basically it is due to the re initialization of a block of memory or because of not freeing it. for ex *memory1 = malloc(100); //100 bytes allocted to memory1 say A blocks *memory2 = malloc(100); //10 bytes allocated to memory2 say B blocks memory1 = memory2; //Mow memory1 too is pointing to B blocks so the Block //A memory pointed by none of the ptrs 1.e 100bytes leak is created.