BPSC is held for Combined Competitive posts and Judicial posts and the syllabus is different for each of the examinations. The official website has the updated syllabus and it is a 100 page word document. Hence helping you with the link: http://www.bpsc.bih.nic.in/Syllabus.htm . You need to clear the Public Service Examination to become a DSP. Once you clear the examination, there is a training period of 2 years post which you are posted as a DSP.