Test preparation

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.