You can go through below books for your preparation

Section A
Quantitative Aptitude & Reasoning
R. S. Aggrawal 

Section B
Data Communication & Networking
CompTIA Network+ Study Guide (Todd Lammle)
Data communication and networking (Forouzan)

C Programming
Let Us C (Yashavant Kanetkar) 
C++ OOP balguruswamy

Operating Systems
Operating System Principles (Silberschatz, Galvin, Gagne)

Section C
Computer Architecture
Computer Organization & Architecture (William Stallings)

Digital Electronics
Digital Design (Morris Mano)
Modern Digital Electronics (R. P. Jain)

Microprocessors
Microprocessor Architecture, Programming & Applications 
with 8085 (Ramesh Gaonkar)
The Intel Microprocessor (Barry Brey