#include <stdio.h>

struct Msg_Header { // struct tag
    int n;
};

typedef struct Msg_Header Msg_Header; // typedef synonym

int main(void) {
    Msg_Header msg_header;

    printf("%zu\n", sizeof(struct Msg_Header));
    printf("%zu\n", sizeof(Msg_Header));
    printf("%zu\n", sizeof msg_header);

    return 0;
}