c programming struct question

[COKEDUDE]

I was looking at this struct tutorial.

https://www.tutorialspoint.com/cprogramming/c_structures.htm

It mentions "The structure tag is optional". How would you refer to your struct if there is no structure tag?

struct {
   char  title[50];
   char  author[50];
   char  subject[100];
   int   book_id;
};  

//something like this? 
struct random_name;

[rproffitt]

Maybe they didn't cover why. I'm reading https://en.cppreference.com/w/c/language/struct#:~:text=Similar%20to%20union%2C%20an%20unnamed,or%20union%20is%20also%20anonymous.

[Schol-R-LEA]

The structure tag is optional because there are instances where you want a one-off structure;

struct {
    int foo;
    char bar[4];
} my_unique_data_structure;  // only struct of this form

The tag is for when you want to name the structure template or type.

struct quux {
    int baz, bang, zing;
};

struct quux whoopie;

You can also declare instances of a named structure following the structure definition, for cases where you know ahead of time that you need at least one structure of that type:

struct quux {
    int baz, bang, zing;
} whoopie;

// later ...
struct quux flarp;

I hope this makes it a bit clearer.