people how developed th caste system

Do you mean how did the the caste system develop? There is no one simple answer since this is something that developed over a long period of time.

http://adaniel.tripod.com/origin.htm

http://www.mtholyoke.edu/~epandit/page2.html

http://internet.cybermesa.com/~rotto/caste1.html

Read carefully and take good notes.