Struct keyword in function parameters, what is the difference?

Question

I wonder, what is the difference between:

struct Node
{
  int data;
  Node *next;
};

and

struct Node
{
  int data;
  struct Node *next;
};

Why do we need struct keyword in second example?

Also, what is the difference between

void Foo(Node* head) 
{
    Node* cur = head;
    //....
}

and

void Foo(struct Node* head) 
{
    struct Node* cur = head;
    //....
}

Answer 1

Only the declarations including struct are valid in C. There is no difference in C++.

However, you can typedef the struct in C, so you don’t have to write it every time.

typedef struct Node
{
  int data;
  struct Node *next;  // we have not finished the typedef yet
} SNode;

SNode* cur = head;    // OK to refer the typedef here

This syntax is also valid in C++ for compatibility.