can someone give me a program which has bugs for practice. I already have a strong theoretical knowledge and now i would like to use this knowledge in practice.
Many open source projects are actively looking for help with their projects, one aspect wanting help is for bug fixing. Rather that looking for examples for practice you could find a real project in an application that interests you and help them to fix real bugs.
A web search for terms such as "open source help wanted" will find many projects plus ideas on how to find projects wanting help.
Signup with the uTest (THE PROFESSIONAL NETWORK FOR TESTERS), they have some example projects for you to look at.
If you succesfull pass the "test" project, then you will be offered paid testing cycles.
Mostly its website testing, but I have done mobile app testing and such :)
As a couple have already mentioned (thank you both) - uTest has a lot of resources for testers of various skills. **Disclaimer, I work at uTest/Applause.
Gigs, You might find value and enjoyment in some of the courses we've setup: http://university.utest.com/
We have a lot of learning and sandbox opportunities so you can play/break/learn in a controlled environment. The best part might be the paid test cycles you'll get invited to as your progress.
I've also learned about good bug reporting through simply reaching out to developers directly online to report a bug. The two most common areas of concern seem to be, 1) is it critical and, 2) is it repeatable?
Check out the link and, as always, I'm happy to answer any questions direct - just tag me in a comment or email me directly at email@example.com.