I received a call from HR initially, and then was scheduled for a technical phone interview. Topics covered in the interview:

• Math
• Basic OS
• Java
• C
• C++

Math:

• How do you derive the sum of N natural numbers using mathematical induction?
• Birthday Paradox: If there are 400 people in a room, what is the probability of at least two people sharing a birthday?
• How many signed integers can be represented using 32 bits?
• What is AU(B ^ C)?
• A problem on the (A U B U C) formula.
• Some questions on Finite Automata and NFA.

C:

• What is the procedure to find an even number without using the modulo operator?
• What is the limitation of the modulo operator in C?
• What is a UNION datatype?

C++:

• What is an Abstract Class and its significance?
• Runtime polymorphism.
• The static keyword.

Java:

• What is the difference between JRE, JDK, and JVM?
• What is a HashMap?
• Is Java call by value or call by reference? (A good question; I was asked this in multiple interviews.)
• OOPs concepts.