Hello Apirant.

You haven't mention which exam are you talking about. Neither have you mentioned you proper name on your account. You should be specific when you ask queries here and change your profile name it appeals to be a spam account. So on the basis of the hashtag you had put in this question I am answering it.

For NIELIT preparation, the candidates can follow the study materials related to GATE CS exam. Using the relevant study material, they should make easy notes for the theoretical subjects, and write all the formulae and tricks for the practical subjects to revise the topics thoroughly during the exams . I am listing some books which might help.

Qualitative and quantitative analysis books:

• Play with Advanced Maths- Abhinay Sharma
• Teach yourself quantitative aptitude- Arun Sharma
• Quantitative Aptitude- R.S. Aggarwal

General Awareness and Aptitude Books:

• A Complete Reference to General Aptitude- GK Publications
• Quantitative Aptitude for All Competitive Examination-  Abhijit Guha
• General Knowledge- Lucents
• General Knowledge 2021- Manohar Pandey
• General Knowledge Manual- Pearson

some books for technical section:

• Multiple Choice Questions For GATE / PSUs- Made Easy Publication
• MCQs On Computer- Dr Alok Kumar
• Analog and Digital Communication- Neha Jain
• Computer Awareness Objective & Subjective- S. R. Behera

Hope this helps you.