Understand How a Pointer to Structure Variable is Sent to a Function

/*
Write a program to understand how a pointer to structure variable is sent to a function 
*/

#include<stdio.h>
struct student {
        char name[20];
        int rollno;
        int marks;
           };
void display(struct student *);
void inc_marks(struct student *);
main( )
{
    struct student stu1 = {"John", 12, 87};
    struct student stu2 = {"Mary", 18, 90};
    inc_marks(&stu1);
    inc_marks(&stu2);
    display(&stu1);
    display(&stu2);
}
void inc_marks(struct student *stuptr)
{
    (stuptr->marks)++;
}   
void display(struct student *stuptr)
{
    printf("Name   - %s\t", stuptr->name);
    printf("Rollno - %d\t", stuptr->rollno);
    printf("Marks  - %d\n", stuptr->marks);
}