The pattern of the UPSC Civil Services Examination, which includes the Indian Administrative Service (IAS), Indian Police Service (IPS), Indian Foreign Service (IFS), Indian Revenue Service (IRS), and other Group A and Group B services, can be summarized as follows:

Preliminary Examination:

•  The Preliminary Examination consists of two objective-type papers (multiple-choice questions)
•  Paper 1: General Studies - 200 marks, 2 hours duration
•  Paper 2: Civil Services Aptitude Test (CSAT) - 200 marks, 2 hours duration
•  Both papers are evaluated for eligibility to appear in the Main Examination
•  Paper 2 (CSAT) is qualifying in nature, and the minimum qualifying marks are determined by the UPSC

Main Examination:

•  The Main Examination consists of nine papers, which are a mix of essay-type and descriptive questions.
•  Paper A: Indian Language (Qualifying Paper) - 300 marks, 3 hours duration
•  Paper B: English (Qualifying Paper) - 300 marks, 3 hours duration
•  Paper 1: Essay - 250 marks, 3 hours duration
•  Paper 2-5: General Studies I, II, III, and IV - 250 marks each, 3 hours duration for each paper
•  Papers 6 and 7: Optional Subject Paper 1 and Paper 2 - 250 marks each, 3 hours duration for each paper
•  The optional subject papers are chosen by the candidates from a list of subjects provided by the UPSC

Personality Test (Interview):

•  The Personality Test, also known as the Interview, is conducted by a board appointed by the UPSC
•  It assesses the candidate's personality, communication skills, leadership qualities, and suitability for a career in public service
•  The interview carries a weightage of 275 marks.

The final selection of candidates is based on the combined score of the Main Examination and the Personality Test (Interview).
It is important to note that the UPSC may introduce changes in the exam pattern from time to time, and it is advisable to refer to the official UPSC notification and website for the most accurate and up-to-date information regarding the exam pattern for the UPSC Civil Services Examination.