calling a struct in c code example

Example 1: struct in C

#include<stdio.h>
#include<string.h>

struct Student{
long int rollNo;
int age;
char name[50];
int totalMarks;
};

int main(){

    struct Student s1;
    //accessing members of the struct
    s1.rollNo = 1232234643;
    s1.age = 10;
    char s[]="Jonathan";
    strcpy(s1.name,s);
    s1.totalMarks = 450;

    printf("RollNumber: %d \nName: %s \nTotal Marks: %d",s1.rollNo,s1.name,s1.totalMarks);

return 0;
}

Example 2: struct in c

typedef struct {
	char cognome[30];
	char nome[20];
	int voto;
}alunno;

Example 3: function inside struct c

typedef struct client_t client_t, *pno;
struct client_t
{
        pid_t pid;
        char password[TAM_MAX]; // -> 50 chars
        pno next;

        pno (*AddClient)(client_t *);  <-- pointer to function    
};

pno client_t_AddClient(client_t *self) { /* code */ } <-- function

int main()
{

    client_t client;
    client.AddClient = client_t_AddClient; // probably really done in some init fn

    //code ..

    client.AddClient(&client);

}