How to Crack TCS Ninja & Digital in 2026: Complete Roadmap, Exam Pattern & Top Q&A

Q1. What is the difference between Call by Value and Call by Reference in C/C++?

Answer: In Call by Value, a copy of the actual variable is passed to the function. Changes made inside the function do not affect the original value. In Call by Reference, the memory address of the variable is passed, allowing the function to directly modify the original variable.

Q2. Explain Object-Oriented Programming (OOP) Pillars with real-world examples.

Answer: OOP is built on four core principles:

• Encapsulation: Wrapping data and methods into a single unit (e.g., a Bank Account class hiding balance variable).
• Abstraction: Hiding internal implementation details and showing only functionality (e.g., driving a car without knowing internal engine combustion).
• Inheritance: Reusing code from a parent class (e.g., ElectricCar inheriting from Vehicle).
• Polymorphism: Ability of a method to take multiple forms (Method Overloading and Method Overriding).

Q3. What is the difference between Primary Key, Unique Key, and Foreign Key in SQL?

Answer: A Primary Key uniquely identifies each row in a table and cannot accept NULL values (only 1 primary key per table). A Unique Key ensures all values in a column are distinct, but allows one NULL value. A Foreign Key references the primary key of another table to establish a relationship.

Q4. How do you find the second highest salary in an Employee table using SQL?

Alternative using OFFSET: SELECT DISTINCT salary FROM Employee ORDER BY salary DESC LIMIT 1 OFFSET 1;

Q5. What is Method Overloading vs Method Overriding in Java?

Answer: Method Overloading occurs within the same class when multiple methods share the same name but have different parameter lists (compile-time polymorphism). Method Overriding occurs when a subclass provides a specific implementation of a method declared in its superclass (runtime polymorphism).