Dear Komal

you cannot. No employee enrolled in a government job is permitted to run a side business or do a side job. It is especially not possible if another (in your case software engineering) job involves receiving  monetary benefits by the IAS.

As per the rules, any govt employee is not allowed to hold any office of profit/another job while still in govt service. In order to do another  you have to resign from the govt job. There are 2 options:

1. Take VRS & then join any other job

2. After retirement(usually at 60 years) an employee is barred from joining another job(presently for 1 year). After  that you may join. But if you write a letter to the DOPT seeking permission for doing another job(which they usually ) before retiring then it is possible.