TCS encompasses one of the most exhaustive interview process. Everything begins with how you have been with your academics. It has an exemption criteria where students scoring above a specific marks are exempted. At my institution, Jamia Millia Islamia (a Central Univ), it was set as 8.77.
The aptitude test forms the most challenging part, so getting exempted from it remains a breather. However, their difficulty level is not constant and it keeps varying on yearly basis. It consists of topics from probability, PnC, sequence and series, pattern recognition, work and time and almost all such topics you can think of. It lasts for almost 80 minutes. I, being exempted, had a rather easy going path.
It's followed by a 10 min Verbal part where they make you write an e-mail. The most challenging process is to use all the key-words that they have specified and address it and undersign it correctly. Those who have been exempted from apti have to appear in this round directly. No one gets exempted from Verbal Ability Round and YES, this is an elimination round, so don't be overconfident.
It's then followed by interviews. Interview is mostly conducted by 5-7 panels and here's where your luck factor comes into play. Here's how my interview went.
M: ME
I: INTERVIEWER
Remember: Even after conducting interviews for 7 hours, I had a cheerful interaction with him. Carry a positive attitude with yourself. They don't want to see a gloomy face which would be repulsive.
M: Good Evening sir. (it was 5 p.m)
I: Good Evening, have a seat.
I: Tell me something about yourself.
M: Told. I told him about my passion for writing and my publications in ToI. He asked a couple of questions based on that.
(Technical)
I: Your favorite subject.
M: Operating System
I: Tell me about few scheduling algorithms
M: Told
I: Tell me about different types of OS
M: Told
I: Explain the entire concept of Memory Management.
M: Told
I: What is thrashing?
M: Sir, not very through with the concept. (He passed a gentle smile, which was not sarcastic).
M: Told him about few structures of memory which he never asked for :P
I: What are Daemon Processes?
M: Told
I: What's the difference b/w Deamon Process and normal process?
M: Told
I: What do you understand by Preemption and Non Preemption?
M: Told.
After a good grilling, he switched over to a programming language.
I told him I'm comfortable with C. I tried to hide Java to the extend that I even did not mention one of the excellent project I made in Java as Java Interviews are deadly :X
I: What do you understand by a pointer?
M: Told
I: How do you declare an array?
M: Told
I: How do you point a pointer to an array?
M: Told
I: How do you make an array of pointers
M: I have no idea what I told him :P
The guys sitting next to him got hold of my TCS Application form and found that I had mentioned 'Chat Server Application" which I forgot to remove from there.
I: In which language did you make this.
M : (OMG!!!) Java
"Okkkay, let's play Java Java now. Something I never wanted to reveal.
I: Explain Polymorphism
M: Explained in detail.
It was this time when I was explaining on an A4 sheet, I saw one of the interviewers nodding in affirmation to the other. I got a hint that they are quite impressed.
I: Explain Function Overloading.
M: Explained in detail.
I: Explain the difference between classes and structures.
M: It was the most exciting part. We rather had an informal discussion where he was explaining me a concept and I was literally arguing with him (Remember, in a positive sense. I was just putting my concepts with confidence).
Finally I was done with Tech. & I was more energetic after leaving the room. The guy who took my interview was damn awesome, both in terms of his knowledge and attitude. He never tried to impose himself, nor to put me under useless trouble.
HR
L: Lady
M: Me
L: She introduced herself.
L: Why you want to join TCS.
M: Ma'am, it's not a streamlined product based company. I see it undertaking various projects and I can always find something that interests me.
L: Then why TCS. Infosys/Wipro, all do the same thing. (She literally nailed me here)
M: I gave a logical answer. I told her that TCS convinced me that it's the right company to work for.
L: Then if any other company would convince you that they are better, you'll shift?
M: Ma'am, this is how the entire corporate sector works.
L: You aware of TCS policy?
M: Yes
L: Why should I believe that you'll follow it?
M: I respect human hours. Since you have given your time to me, I'll definitely reciprocate.
L: You have any issues in relocating in any other part?
M: No, not at all.
L: Thank you.
PS: The best part of this was that TCS was the first company visiting the Campus & I got the job offer, making it my first placement too.