What is a dangling pointer?

Answer 1

If u know basics of dynamic memory allocation.....
then when we allocate memory then a pointer to start of memory is returned say by syntax like int *p =(*int)malloc(size in bytes);
But when u use free function to clear the memory.....
The memory gets cleared and pointer is NOT POINTING TO ANYTHING..SUCH POINTER KNOWN AS DANGLING POINTERS

Answer 2

An addition to Saurabh B's answer: Those "loose hanging" pointers can be avoided by setting

*p = NULL

after free'ing it and checking via e.g.

if (*p == NULL) return 0;