The keyword ‘struct’ is optional in C++

In C, struct keyword must be used for declaring structure variables, but it is optional in C++.

For example, following program gives error in C and works in C++.

struct node
{
   int x;
   node *next; // Error in C, struct must be there. Works in C++
};
 
int main()
{
   node a;  // Error in C, struct must be there. Works in C++
}

And following program works in both C and C++.

struct node
{
   int x;
   struct node *next;  // Works in both C and C++
};
 
int main()
{
   struct node a;  // Works in both C and C++
}