The pattern of the UPSC prelims exam consists of two objective papers: General Studies I and General Studies II (CSAT). General Studies I covers topics such as current affairs, history, geography, polity, environment, and economics, while General Studies II tests candidates' aptitude, comprehension, and communication skills. Each paper contains 100 questions, with a total duration of two hours for both papers, and there is negative marking for incorrect answers. The prelims serve as a screening test, and scores do not count towards the final merit list, but qualifying is essential for progressing to the Mains.