Civil Servant (IAS/PCS)

You need to start with basic NCERT books for prelims as to cover General studies.
All NCERT books from class VI on wards are on all the subjects. Some study materials particularly for subjects such as economics polity and Indian culture are required apart from NCERT books.
For purpose of mains, optional is much important to choose. CSAT is not so negligible. So, a lot of practice is required. Public administration history psychology are quite advisable. The rest depends on your interests.

To become an IFS officer, you should have completed your graduation. After graduation or while pursuing graduation, you can prepare for UPSC CSAT exam for IAS. After clearing the CSAT, which is conducted every year and clearing all the rounds including CSAT, Mains, and personal interview, you can become an IFS officer.

Hello Priyam,
You can join Indian Foreign Services after cleaning civil services examination conducted by UPSC. You can appear for this after completing graduation.

Yes, you can do that. You can prepare for IAS after pursuing BCA. There is no limitation of courses for IAS. The only requirement is that you must be a graduate for IAS exams from a recognized university.

Every year, a lot of science graduates and post-graduates crack Civil Service Examination. Any graduate with good academic records, self-confidence, with proper planning and preparation can crack Civil Service examination. All the Best!

You are eligible to appear for Civil Services exam on completion of B.Tech IT. You can do Civil Services Examination preparations along with your engineering studies but it requires lot of planning and efforts. Most of IT graduates do dedicated training and preparations after B.Tech to appear in Civil Services Examination.

Best Books for IAS preparation:-
Indian polity by Laxmikanth 5TH Edition
Geography of India by Majid Husain
Indian Economy by Ramesh Singh
General Studies Based on NCERT Syllabus
Certificate Physical and Human Geography

You can choose according to your interest.
Every stream has own importance and value.
I prefer science stream.
But you can choose according to your interest, knowledge and understanding.

It's been a quite well settled and conventional thing to notice about Civil services (BA). Humanities has served a better result always. Rest depends on your interest and love for a subject as you need in your Mains.