IAS exam are conducted in three phase i. e prelims, mains and personal interview
In prelims, there are 2 parts -General studies and CSAT and each carry 200 marks in which topics are mostly on logical reasoning, analytical skill, histroy of India, Indian and world geography, political system, governance Constitution, social justice and IR, and current affairs.
In mains exam there are 7papers including 2 optional subject in which you can choose subject of your choice... In physics, Botony, Agriculture, philosophy, sociology, statistics, zoology and many more.. You can choose any 2 option from this subjects
Hope this information will help you