GATE

HI Shruti,
Here I am recommending some of the GATE Computer Science preparation books based on following metrics:
1. Adhering to GATE syllabus
2. Offering easy to understand concepts
3. Popularity of the book
4. Toppers recommended books
The following books are recommended for preparation of GATE Computer Science and Information Technology.
Programming & Data Structure
GATE Questions from this subject are easy and sometimes it may waste your time due to recursive functions in programs. For getting good score, you shall focus more on the topics such as pointers, recursion, trees, and stacks.
Book Name: The C Programming language, Authors Name: Brian W. Kernighan , Dennis M. Ritchie, Edition: 2
Book Name: Classic Data Structures, Authors Name: Debasis Samanta, Edition: 2
These two books are comprehensive book for those who study Computer Concepts and C Programming, Computer Programming, Programming Methodology and Data Structures. It has all the content required that helps in making a clear understanding of C Programming concepts. These two book is quintessential for candidates studying C Programming.
Algorithms
Questions from algorithms require good understanding of design techniques. New problems in algorithms may consume your time in GATE but easy problems can be answered quickly. Many GATE questions are directly appears from the following book. This book is easy to read but everyone finds that to read each topic it may take more time due to lengthy explanation.
Book Name: Introduction to Algorithms, Authors Name: Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein, Edition: 3
All computer algorithms can be understood clearly by perusing the contents of Introduction To Algorithms. Although this covers most of the important aspects of algorithms, the concepts have been detailed in a lucid manner.
Computer Networks
GATE questions from this subject have two types. First type can be answered quickly and other type of questions may need 3 to 5 minutes to get the answer. First type of questions may include from the topics: IP addressing, Routing concepts and TCP/UDP. Second type of questions from the topics: Ethernet problems, Congestion control, and Sliding Window Protocols. The following book has all concepts required for GATE syllabus.
Book Name: Computer Networking: A Top-Down Approach, Authors Name: James F. Kurose, Keith W. Ross, Edition: 6
All the best.

Hi,
The Graduate Aptitude Test in Engineering (GATE) is an examination that primarily tests the comprehensive understanding of various undergraduate subjects in engineering and science.
The score is used for admissions to various post-graduate education programs (e.g. Master of Engineering, Master of Technology, Doctor of Philosophy) in Indian higher education institutes, with financial assistance provided by MHRD and other government agencies.
The following are eligible to take GATE:
1)Bachelor's degree holders in Engineering /Technology/Architecture (4 years after 10+2/ Post-B.Sc./ Post-Diploma) and those who are in the final year of such programs.
2) Master's degree holders in any branch of Science/ Mathematics/Statistics/Computer Applications or equivalent and those who are in the final year of such programs.
3) Candidates in the second or higher year of Four-year integrated master's degree programs (Post-B.Sc.) in Engineering/Technology.
4) Candidates in the fourth or higher year of Five-year integrated master's degree programs or Dual Degree programs in Engineering/Technology
You may also refer: http://www.gate.iitr.ernet.in

There are a number of books which you can follow for the GATE, just read thoroughly each chapter whichever book you follow. I am suggesting you some books:-
for production: - Production operations by Allen Robert (vol-1 & vol-2),
for Drilling - Well engineering and construction by H. Rabia,
for Reservoir - fundamentals of reservoir engineering by L.P Dake & book by Tariq Ahmed and for
Logging - Log interpretation principles and operations- Schlumberger.
Also, there are many books and handbooks which you can follow. Just remember don't follow so many books but complete each section of petroleum engineering from one book of each section.
Thank You!