whilep != NULL count++; p = p-next; return count;

This code is a function that counts the number of nodes in a linked list.

Here's how it works:

1. The function takes in a pointer to the head of the linked list.
2. It initializes a count variable to 0.
3. It loops through the linked list using a while loop.
4. At each iteration, it increments the count variable by 1 and updates the pointer to the next node in the list.
5. Once the loop has finished, it returns the final count of nodes in the linked list.

Overall, this function is a simple and efficient way to determine the size of a linked list