I want to make a University Management system in which i can add student name ,rollno, edit delete display the data of students.

Answer 1

use SQL(MySQL) for that
create a database
use database
create a table with fields,datatypes&constraints //P.K. on rollno
for adding , use INSERT
for editing , use UPDATE
for deleting , use DELETE FROM

Answer 2

So you would be happy with my Cobol code for this? Please read the following and update your post to provide enough information to make it possible to help. It should be noted most people here will fix your code. But, we don't write it for you.
https://www.sololearn.com/Discuss/333866

Answer 3

I don't know which language you are working on. But when I look your tag, your tag is union. I guess you want to do it in C language. If you will use C you should use structs to do it. Using union is also a choice. But if you will use union you should use it in struct to control the memory management. If you will use other languages you can use sql. If you choose C# , you can use entity framework to make your things easy. Also you can work with diagrams(in sql) to see your database clearly.