For the IAS Preliminary Exams, GS Paper II is a qualifying paper which needs just 33% marks. From those who qualify in Paper II, the marks in GS I will decide the eligible candidates for CS(Mains) Exams. 

General Studies II is a 200 marks MCQ paper of two hours duration. The syllabus includes Comprehension, Interpersonal skills including communication skills, Logical reasoning and analytical ability, Decision-making and problem-solving, General Mental ability, Basic numeracy (numbers and their relations, orders of magnitude etc) and Data interpretation (charts, graphs, tables, data sufficiency etc).

The decider General Studies Paper I is again a 200 marks MCQ paper of two hours duration. The syllabus is very vast which covers   (a)  Current events of national and international importance  (b)  History of India and Indian National Movement  (c)  Indian and World Geography – Physical, Social, Economic Geography of India and the World  (d)  Indian Polity and Governance – Constitution, Political System, Panchayati Raj, Public Policy, Rights Issues etc.  (e)  Economic and Social Development - Sustainable Development, Poverty, Inclusion, Demographics, Social Sector initiatives etc.  (f)  General issues on Environmental Ecology, Bio-diversity and Climate Change (do not require subject specialization)  and  (g) General Science.

The Four General Studies papers in the Mains exams covers a similar set of topics and are subjective in nature. It needs a focused approach on a more detailed range of the same topics. Preparing for the Preliminary Exams should supplement the Mains preparation. The four papers broadly cover:

Paper I:  Indian Heritage and Culture, History and Geography of the World and Society
Paper II:  Governance, Constitution, Polity, Social Justice and International relations
Paper III: Technology, Economic Development, Bio-diversity, Environment, Security and Disaster Management
Paper IV:  Ethics, Integrity and Aptitude