I'm in 1st year of cse so please suggest me the best book to prepare for GATE??

Hello,
These are the books you should use for your preparations for GATE Computer Engineering:

1.An Introduction to Formal Languages and Automata  by PeterLinz
2.Discrete Mathematics and Its Applications by   KennethRosen
3.Introduction to Algorithms        by  C.L.R.S
4.Database Systems                 by      Elmasri& Navathe
5.Computer System Architecture      by     MorrisMano
6.The C Programming Language     by       DennisRitchie
7.Data Communications and Networking by    Forouzan
8.Operating System Concepts     by     Galvin
9.Data Structures Using C            by    Tenenbaum
10.Compilers:Principles,Techniques,& Tools by   Ullman
11.Modern Digital Electronics   by      R. P.  Jain
Good luck.