NULL pointer
NULL is used to indicate that the pointer doesn’t point to a valid location. Ideally, we should initialize pointers as NULL if we don’t know their value at the time of declaration. Also, we should make a pointer NULL when memory pointed by it is deallocated in the middle of a program.
Dangling pointer
Dangling Pointer is a pointer that doesn’t point to a valid memory location. Dangling pointers arise when an object is deleted or deallocated, without modifying the value of the pointer, so that the pointer still points to the memory location of the deallocated memory.