Program in C to enter student information and find the sum and percentage

 Program in C to enter student information and find the sum and  percentage  Using array of structure variable 

#include<stdio.h>
#include<stdlib.h>
 struct Date
  {
    int day;
    int month;
    int year;
  };
  struct Student
    {
     int roll;
     char name[30];
     char clas[10];
  struct Date dob;
  int marks[5];
 };
  
   void Input(struct Student *s1)
     {
             int i; 
        printf("\nEnter following studetnt details.\n");
        printf("Roll No. :-");
      scanf("%d",&s1->roll);
      printf("Name :-");
      fflush(stdin);
      gets(s1->name);
      printf("Class :-");
      scanf("%s",s1->clas);
      printf("Date of Birth :-");
      scanf("%d%d%d",&s1->dob.day,&s1->dob.month,&s1->dob.year);
      printf("Five Subject marks :-");
      for(i=0;i<5;i++)
       scanf("%d",&s1->marks[i]);
  }
 void display(struct Student *s1)
    {
     int i;
                printf("\n%4d      %s\t      %s\t%d-%d-%d\t",s1->roll,s1->name,s1->clas,s1->dob.day,s1->dob.month,s1->dob.year);;
     for(i=0;i<5;i++)
       printf("%6d",s1->marks[i]);
      printf("%6d\t  %.2f",TotalMarks(s1),TotalMarks(s1)/5.0);
    }
 int TotalMarks(struct Student s1)
  {
        int sum=0,i;
        for(i=0;i<5;i++)
     sum+=s1.marks[i];
     return sum;
  }
  
  int main()
   {
     int ch,i=0,j;
     struct Student s[20];
     while(1)
        {
      printf("Press 1 to insert student details.");
      printf("\nPress 2 to show student details.");
   printf("\nPress 3 to exit.");
      printf("\nEnter your choice number:-");
      scanf("%d",&ch);
        switch(ch)
           {
             case 1:system("cls");
      Input(&s[i]);
                   i++;
                  break;
             case 2:system("cls");
         printf("\n***********************************************************************************************************\n");
             printf("Roll No.    Name\t     Class\tDate of birth\t   sub1  sub2  sub3  sub4   sub5  Sum\tPercentage.");
            printf("\n***********************************************************************************************************\n");
         for(j=0;j<i;j++)
    display(&s[j]);
   case 3:exit(0);
   default:printf("Wrong choice.");
         }
   }
     return 0;
   }

Output:-