Here are the 10 most frequently asked questions that freshers encounter in technical interviews. These cover basics of programming, databases, and problem-solving.

1. Explain the difference between a compiler and an interpreter.

• Compiler converts the entire source code into machine code before execution.
• Interpreter executes code line by line.

2. What is the difference between stack and heap memory?

• Stack: Stores local variables, method calls; fast but limited size.
• Heap: Stores objects; larger but slower memory allocation.

3. Explain OOP concepts with examples.

• Abstraction: Hiding details (e.g., abstract class).
• Encapsulation: Wrapping data and methods in a class.
• Inheritance: Reusing properties from another class.
• Polymorphism: Same method behaving differently in different contexts.

4. What are the differences between C, C++, and Java?

• C: Procedural language.
• C++: Supports both procedural and OOP.
• Java: Purely OOP, runs on JVM, platform-independent.

5. Explain SQL vs NoSQL databases.

• SQL: Relational, structured, schema-based (MySQL, SQL Server).
• NoSQL: Schema-less, flexible, for big data and documents (MongoDB).

6. What are data structures and why are they important?

• Ways to organize and store data efficiently.
• Examples: Array, Linked List, Stack, Queue, Tree, Graph.

7. Write a program to reverse a string.

• Answer:

  string str = "hello";
  char[] arr = str.ToCharArray();
  Array.Reverse(arr);
  Console.WriteLine(new string(arr));

8. What is the difference between == and === in JavaScript?

• ==: Compares values after type conversion.
• ===: Compares values and types strictly.

9. What are HTTP methods commonly used in APIs?

• GET, POST, PUT, DELETE, PATCH for CRUD operations.

10. How do you explain the SDLC (Software Development Life Cycle)?

• Phases: Requirement gathering → Design → Development → Testing → Deployment → Maintenance.

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Tip: Practice coding small programs, algorithms, and SQL queries daily.