Top 100+ Most asked Computer Science Engineering Interview Questions for Job Preparation

Question: 26. What is process scheduling? Explain different types of schedulers.

Answer: Process scheduling determines the execution order of processes. Types include long-term, short-term, and medium-term schedulers.

Question: 27. How does virtual memory work?

Answer: Virtual memory uses disk space as an extension of RAM, allowing processes to execute beyond physical memory limits.

Question: 28. Explain deadlock and how it can be prevented.

Answer: Deadlock is a situation where processes wait indefinitely for resources. Prevention includes resource ordering and avoiding circular waits.

Question: 29. What is the difference between process and thread?

Answer: A process is an independent executing instance, while a thread is a lightweight unit of execution within a process.

Question: 30. Describe the Round Robin scheduling algorithm.

Answer: Round Robin assigns time slices to processes in a cyclic order, ensuring fair CPU time distribution.

Question: 31. Explain the concept of paging and segmentation.

Answer: Paging divides memory into fixed-size blocks, while segmentation divides it into variable-size logical segments.

Question: 32. What are race conditions? How can they be avoided?

Answer: Race conditions occur when multiple threads access shared resources simultaneously. They can be avoided using locks, mutexes, or semaphores.

Question: 33. How does the banker's algorithm prevent deadlock?

Answer: The banker's algorithm ensures resources are allocated safely by checking if allocation would leave the system in a safe state.

Question: 34. Explain the difference between preemptive and non-preemptive scheduling.

Answer: Preemptive scheduling allows process interruption, while non-preemptive scheduling completes a process before switching.

Question: 35. What is a system call, and how does it work?

Answer: A system call is a user-space request to the kernel for services like file operations or process control.

Question: 36. Describe the difference between multitasking and multithreading.

Answer: Multitasking runs multiple processes, while multithreading runs multiple threads within a process.

Question: 37. What is context switching? When does it occur?

Answer: Context switching is saving a process state and restoring another. It occurs during process scheduling or interrupts.

Question: 38. What is the purpose of a mutex in process synchronization?

Answer: A mutex ensures only one thread accesses a critical section at a time to prevent race conditions.

Question: 39. Explain inter-process communication (IPC).

Answer: IPC allows processes to exchange data using mechanisms like shared memory, message passing, or pipes.

Question: 40. What are the differences between monolithic kernels and microkernels?

Answer: Monolithic kernels manage all OS functions, while microkernels handle core services, delegating others to user space.

Question: 41. How does demand paging work in virtual memory?

Answer: Demand paging loads pages into memory only when needed, reducing memory usage.

Question: 42. What are inodes in file systems?

Answer: Inodes store metadata about files, like size, permissions, and disk block locations.

Question: 43. What is the difference between paging and swapping in memory management?

Answer: Paging moves memory pages between RAM and disk, while swapping moves entire processes.

Question: 44. Describe thrashing and how it can be avoided.

Answer: Thrashing occurs when excessive paging reduces performance. It can be avoided by allocating sufficient memory or adjusting multiprogramming levels.

Question: 45. How do signal handlers work in UNIX/Linux systems?

Answer: Signal handlers execute specific functions when a process receives a signal, overriding default behavior.

Question: 46. What is scheduling starvation, and how can it be resolved?

Answer: Starvation occurs when low-priority processes are indefinitely delayed. It can be resolved using aging to increase priority over time.

Question: 47. Explain the concept of priority inversion and its solution.

Answer: Priority inversion occurs when a high-priority task waits for a lower-priority task. Solutions include priority inheritance.

Question: 48. What is the role of a scheduler in an operating system?

Answer: The scheduler manages CPU allocation to processes, optimizing performance and resource utilization.

Question: 49. How does process synchronization prevent race conditions?

Answer: Process synchronization uses mechanisms like locks, semaphores, and monitors to ensure safe shared resource access.

Question: 50. What are the different states of a process lifecycle?

Answer: Process states include new, ready, running, waiting, and terminated.

3. Databases

Question: 51. What is normalization, and why is it important?

Answer: Normalization organizes data to reduce redundancy and improve data integrity.

Question: 52. Explain ACID properties in databases.

Answer: ACID stands for Atomicity, Consistency, Isolation, and Durability, ensuring reliable transactions.

Question: 53. What is a foreign key? How does it differ from a primary key?

Answer: A foreign key links tables and references a primary key in another table; a primary key uniquely identifies a record.

Question: 54. What is the difference between SQL and NoSQL databases?

Answer: SQL databases are relational and use structured schemas, while NoSQL databases are non-relational and handle unstructured data.

Question: 55. How would you optimize a slow-running SQL query?

Answer: By indexing, analyzing query plans, optimizing joins, and avoiding SELECT *.

Question: 56. Explain transaction isolation levels in databases.

Answer: Isolation levels (READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE) define how transactions interact with each other.

Question: 57. What are triggers and when would you use them?

Answer: Triggers are automatic actions executed in response to certain database events.

Question: 58. Explain the concept of indexing and how it improves database performance.

Answer: Indexing creates a data structure to allow faster search and retrieval.

Question: 59. How does database partitioning work?

Answer: Partitioning divides data into smaller segments for improved manageability and performance.

Question: 60. What is a JOIN in SQL, and what are the different types of joins?

Answer: JOIN combines data from multiple tables. Types include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN.

Question: 61. What is a view in a database? How is it different from a table?

Answer: A view is a virtual table based on a query, whereas a table physically stores data.

Question: 62. Explain the difference between HAVING and WHERE clauses in SQL.

Answer: WHERE filters rows before aggregation; HAVING filters after aggregation.

Question: 63. What are stored procedures? How do they differ from functions?

Answer: Stored procedures perform tasks and can return multiple values, while functions return a single value.

Question: 64. Explain the concept of sharding in distributed databases.

Answer: Sharding partitions data across multiple servers for scalability.

Question: 65. How does deadlock occur in databases? How can it be resolved?

Answer: Deadlock occurs when transactions wait indefinitely for resources. It can be resolved by timeouts or deadlock detection algorithms.

Question: 66. What is a schema in a database?

Answer: A schema defines the structure of a database, including tables, columns, and relationships.

Question: 67. How do cascading deletes work in relational databases?

Answer: Cascading deletes automatically remove dependent rows when a referenced row is deleted.

Question: 68. What is denormalization, and when is it beneficial?

Answer: Denormalization combines tables to improve read performance, often used in analytics.

Question: 69. How would you implement pagination in a SQL query?

Answer: By using LIMIT and OFFSET or ROW_NUMBER.

Question: 70. What are database locks, and what are their types?

Answer: Locks prevent concurrent access issues. Types include shared, exclusive, and row-level locks.

Question: 71. What are aggregate functions in SQL? Give examples.

Answer: Aggregate functions perform calculations on multiple rows. Examples: COUNT(), AVG(), MAX(), MIN(), SUM().

Question: 72. How would you enforce referential integrity in a relational database?

Answer: By using foreign keys with constraints like ON DELETE and ON UPDATE.

Question: 73. Explain the differences between horizontal and vertical scaling in databases.

Answer: Horizontal scaling adds more servers; vertical scaling increases server capacity.

Question: 74. How does replication work in databases?

Answer: Replication copies data from one server to others for redundancy and scalability.

4. Object-Oriented Programming (OOP)

Question: 75. What is inheritance in OOP? Explain with an example.

Answer: Inheritance allows one class to derive properties and behaviors from another. Example: A Dog class inherits from an Animal class.

Question: 76. What is the difference between polymorphism and overloading?

Answer: Polymorphism allows one interface with multiple implementations; overloading defines multiple methods with the same name but different parameters.

Question: 77. How do abstract classes differ from interfaces?

Answer: Abstract classes can have implementations; interfaces only define methods without implementation.

Question: 78. Explain the concept of encapsulation in OOP.

Answer: Encapsulation restricts direct access to an object's data, exposing only necessary parts.

Question: 79. What is constructor chaining in object-oriented programming?

Answer: Constructor chaining occurs when one constructor calls another in the same or a parent class.

Question: 80. How would you implement multiple inheritance in a language that doesn't support it directly (e.g., Java)?

Answer: By using interfaces.

Question: 81. What is the diamond problem, and how is it resolved?

Answer: The diamond problem occurs with multiple inheritance when a class inherits the same base class via different paths. It is resolved using virtual inheritance or interfaces.

Question: 82. Explain method overriding and how it differs from overloading.

Answer: Overriding changes a method's behavior in a subclass; overloading defines multiple methods with the same name but different parameters.

Question: 83. What are design patterns? Give an example of a singleton pattern.

Answer: Design patterns are reusable solutions to common problems. Singleton ensures a class has only one instance.

Question: 84. Explain the SOLID principles of object-oriented design.

Answer: SOLID principles ensure maintainable and scalable OOP designs: Single Responsibility, Open-Closed, Liskov Substitution, Interface Segregation, Dependency Inversion.

Question: 85. What is the difference between aggregation and composition in OOP?

Answer: Composition implies ownership and lifecycle management; aggregation does not.

Question: 86. How does late binding work in polymorphism?

Answer: Late binding resolves method calls at runtime, allowing dynamic method invocation.

Question: 87. Explain dependency injection and its benefits.

Answer: Dependency injection provides objects their dependencies, improving testability and modularity.

Question: 88. What are access modifiers in OOP? Explain the difference between public, private, and protected.

Answer: Access modifiers control visibility. Public: accessible everywhere; Private: within the class; Protected: within the class and subclasses.

Question: 89. How is exception handling implemented in OOP languages?

Answer: Using try-catch blocks, custom exceptions, and finally blocks.

Question: 90. What is a virtual function, and why is it used?

Answer: A virtual function allows method overriding in derived classes for runtime polymorphism.

Question: 91. What is the Liskov Substitution Principle?

Answer: Subtypes must be substitutable for their base types without altering functionality.

Question: 92. How does garbage collection work in OOP languages like Java?

Answer: Garbage collection automatically reclaims memory by identifying and removing unused objects.

Question: 93. What is the difference between shallow copy and deep copy of objects?

Answer: Shallow copy copies references, not objects; deep copy duplicates objects entirely.

Question: 94. What is static binding, and when does it occur?

Answer: Static binding occurs at compile time, binding methods to calls based on the declared type.

Question: 95. What is duck typing in object-oriented languages?

Answer: Duck typing determines object compatibility based on methods and properties rather than inheritance.

5. Networking

Question: 96. What is the OSI model? Explain each layer.

Answer: The OSI model has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, Application, each handling specific network functions.

Question: 97. What is the difference between TCP and UDP?

Answer: TCP is connection-oriented and reliable; UDP is connectionless and faster but less reliable.

Question: 98. How does HTTP work, and what are HTTP status codes?

Answer: HTTP is a request-response protocol. Status codes indicate the response type (e.g., 200 OK, 404 Not Found).

Question: 99. What is DNS and how does it resolve domain names?

Answer: DNS translates domain names to IP addresses using a hierarchical lookup.

Question: 100. Explain the concept of IP addressing and subnetting.

Answer: IP addressing assigns unique identifiers; subnetting divides networks into smaller segments for efficient use.

Question: 101. What is ARP (Address Resolution Protocol)?

Answer: ARP maps IP addresses to MAC addresses in a local network.

Question: 102. Explain the difference between IPv4 and IPv6.

Answer: IPv4 uses 32-bit addresses; IPv6 uses 128-bit addresses and offers better scalability and security.

Question: 103. What are the differences between firewall and proxy?

Answer: A firewall filters network traffic; a proxy acts as an intermediary for requests.

Question: 104. What is SSL/TLS, and how does it provide security?

Answer: SSL/TLS encrypts data in transit for secure communication.

Question: 105. What is the difference between a router and a switch?

Answer: A router connects networks; a switch connects devices within a network.

Question: 106. Explain the concept of network congestion control.

Answer: Congestion control manages data flow to prevent overwhelming the network.

Question: 107. What is NAT (Network Address Translation), and why is it used?

Answer: NAT translates private IP addresses to a public IP, conserving IP addresses.

Question: 108. Explain the role of load balancers in networking.

Answer: Load balancers distribute traffic across multiple servers to ensure availability and performance.

Question: 109. What is ICMP, and what is its purpose?

Answer: ICMP diagnoses network issues, sending error messages (e.g., ping).

Question: 110. What is the difference between a VPN and a VLAN?

Answer: A VPN secures communication over the internet; a VLAN groups devices in a virtual network.