As you know though structure we can process data record by
record that is why structure is called user defined data type. In some specific
case you nested structure where a structure is inside of a structure. For example
when process a student record with their dob. Take a look on following example.
#include<stdio.h>
#include<conio.h>
#include<string.h>
typedef struct
s
{
int roll;
char
name[10];
struct d
{
int
dd,mm,yy;
}dob;
}student;