Top 30 IBM interview questions and answers

Imagine the scene: you’re seated across from a panel of seasoned interviewers at IBM, their faces reflecting curiosity and scrutiny. The air is thick with the weight of expectations, and you can hear your heart pounding in your chest. This moment is the culmination of years of learning, experimenting, and dreaming about a career in technology. You recall late nights spent poring over coding challenges, mastering algorithms, and the countless hours dedicated to grasping complex concepts. Suddenly, the interviewer leans in and asks you to explain process scheduling. You pause, feeling nervous and excited, realizing this is your chance to shine.

IBM is known for asking a wide variety of questions that span across technical, behavioral, and domain-specific areas. From coding challenges and system design to questions about core concepts like process scheduling or database management, the interview process tests your depth of knowledge and problem-solving skills. In this blog, we’ll walk you through 30 of the most common IBM interview questions, giving you a clear understanding of what to expect. By mastering these questions, you can transform a potentially daunting interview into an opportunity to showcase your expertise, confidence, and passion for technology.

Let’s explore the operating systems (OS) questions frequently asked in IBM interviews!

IBM operating systems interview questions#

In this section, we’ll dive into key operating systems (OS) interview questions that IBM typically asks, focusing on essential concepts and principles that every aspiring candidate should understand.

Following are the questions with respective answers:

1. What is the process scheduling?
   Process scheduling is a core function of an operating system (OS) that decides which processes run at any given time. The OS maintains a queue of processes and allocates CPU time to each based on scheduling algorithms like:

• Round robin: In this algorithm, each process is given a time slice, and once that time is up, it moves to the back of the queue.

• First-come-first-serve (FCFS): It schedules the processes in the order they arrive; the first to arrive gets CPU time.

• Shortest job next (SJN): In this scheduling algorithm, the CPU is allocated to the process with the shortest execution time.

2. What is a deadlock in operating systems?
   A deadlock occurs when two or more processes cannot proceed because each is waiting for the other to release resources. Operating systems can handle this issue using deadlock detection and avoidance algorithms.
   

3. What is the virtual memory in OS?
   Virtual memory is a memory management capability that allows an OS to use disk space to simulate additional RAM. When a program accesses memory that is not currently in RAM, the OS retrieves it from disk storage, which may slow down performance but allows for multitasking. This enables a computer to run larger applications than what its physical memory can accommodate.
   

4. What is the virtual memory in OS?
   Virtual memory is a memory management capability that allows an OS to use disk space to simulate additional RAM. When a program accesses memory not currently in RAM, the OS retrieves it from disk storage, which may slow down performance but allows multitasking. This enables a computer to run larger applications than its physical memory.
   

5. How do you handle a page fault in OS?A page fault occurs when a program tries to access a page not currently in physical memory. The operating system handles this by:

• Interrupting the current process

• Saving its state

• Loading the required page from disk into memory (paging

6. What are the semaphores?Semaphores are synchronization tools that control access to a common resource that multiple processes use. A semaphore uses two operations:

• Wait (P): It decrements the semaphore value if it exceeds zero; otherwise, it blocks the process.

• Signal (V): It increments the semaphore value, waking up a waiting process if necessary.

7. What’s the difference between mutex and semaphore?

   1. Mutex: It is a lock mechanism that allows only one thread to access a resource at any given time, ensuring exclusive access.

   2. Semaphore: This mechanism allows multiple threads to access a resource simultaneously up to a defined limit. It is important to note that read access to multiple threads can be given; however, write access is exclusive, and only one thread can have it.
      

8. What’s the difference between short-term, medium-term, and long-term schedulers?

• Short-term scheduler (CPU scheduler): It selects which process in the ready state should execute next.

• Medium-term scheduler: It temporarily removes processes from memory (swapping out) and may bring them back later (swapping in).

• Long-term scheduler: It determines which processes are admitted to the system for processing.

9. What is LRU cache?
   The least recently used (LRU) cache is a data structure that evicts the least recently used items first when it reaches its limit. An LRU cache stores a limited number of web pages in a web browser. When a new page is visited, and the cache is full, the least recently accessed page is removed.
   

10. Differentiate between processes and threads in the context of an operating system.

• Processes: These are independent execution units that contain their own memory space.

• Threads: These are the smallest units of processing that can be scheduled within a process, sharing the same memory space. A web browser can have multiple processes (one for each tab) and multiple threads within those processes (for rendering, scripting, etc.), allowing efficient multitasking.

11. In the context of the UNIX operating system, what is the purpose of the sudo command?
    sudo stands for “superuser do.” It allows permitted users to execute a command as the superuser (root) or another user. It’s commonly used to perform administrative tasks that require elevated permissions. Running sudo apt-get update in a Unix-based system updates the list of available packages by temporarily granting the user root privileges.

Software development life cycle (SDLC) and testing#

Knowledge of software development processes is vital for developers, especially for IBM interview preparation. Understanding the SDLC ensures that software is developed systematically, while testing plays a crucial role in delivering high-quality products that meet user requirements.

12. What’s the difference between SDLC and STLC?

• SDLC (Software development life cycle): This approach focuses on the entire development process, including the stages of requirement analysis, design, implementation, and maintenance.

• STLC (Software testing life cycle): This process concentrates on testing processes that ensure software quality. Phases include test planning, test case development, and test execution.

13. What is the software development life cycle (SDLC)?
    The software development life cycle (SDLC) is a structured process that systematically guides high-quality software development through a series of phases. The SDLC ensures software meets technical specifications and user requirements, minimizing errors and inefficiencies. Each phase in the SDLC builds on the previous one, creating a comprehensive approach to development:

    1. Requirement analysis: This phase includes understanding and documenting what the software needs to achieve.

    2. Design: In this phase, planning the architecture and detailed software specifications are finalized.

    3. Implementation: The developers do the required coding of the software based on design documents.

    4. Testing: The software quality assurance engineers identify and fix issues to ensure functionality and quality.

    5. Deployment: The team releases the software to users once its internal testing and development is complete.

    6. Maintenance: This phase requires updating and refining software as needed.
       

14. What are the different phases of the software testing life cycle (STLC)?
    The software testing life cycle (STLC) is a sequence of software testing phases that ensures the software product’s quality and functionality. Unlike SDLC, which covers all aspects of development, the STLC focuses solely on testing activities to detect defects and validate that the product meets user and business requirements. Each phase in the STLC contributes to a structured testing approach:

    1. Requirement analysis: In this initial phase, the testers review requirements to understand what needs testing.

    2. Test planning: In this phase, a test strategy, scope, and resources are finalized by creating a test plan.

    3. Test case development: The software quality assurance engineers write detailed test cases based on requirements.

    4. Environment setup: The hardware and software environments for testing are set up in this phase to prepare for the testing once the developers finish coding.

    5. Test execution: The actual testing is carried out in this phase by running test cases to detect defects.

    6. Test cycle closure: The test cycle ends with analyzing the results, creating test closure reports, and determining whether product quality meets standards.

Database management systems (DBMS)#

Having a solid grasp of databases is essential for IBM technical interview preparation. Understanding DBMS concepts allows developers to design applications that efficiently store, manipulate, and retrieve data while maintaining data integrity and security.

15. What is a database management system (DBMS)? What are its advantages over traditional file systems?
    DBMS is a software for creating and managing databases. In a DBMS like Oracle, data can be easily queried with SQL to retrieve specific information, whereas, in a traditional file system, you might need to manually search through files. Following are a few advantages over a file system:

• Data integrity

• Enhanced security

• Ease of data retrieval

16. What are the ACID properties of a transaction in the context of a database management system?

• Atomic: All operations in a transaction are treated as a single unit.

• Consistent: It ensures the database moves from one valid state to another.

• Isolated: It makes sure that the transactions occur independently without interference.

• Durable: It ensures that the changes made by committed transactions are permanent.
  When processing an online order, the transaction must ensure that the inventory is updated, payment is processed, and the order confirmation is sent—all or none of these actions must occur.

17. What is relational algebra in the DBMS system?

• Formal language: It provides a set of operations to manipulate relations.

• Operations: It includes selection, projection, and join.
  Using relational algebra, you can express a query to find all customers in a specific city by using the selection operation on the customer table.

18. What’s the difference between RDBMS and OODBMS?

• RDBMS (Relational database management system): It uses tables to represent data, where each row is a record, and each column is a field. Data is organized in a structured format with predefined relationships among tables.

• OODBMS (Object-oriented database management system): It stores data as objects, similar to object-oriented programming. Each object encapsulates both data and behavior, allowing for complex data representations.In an RDBMS like MySQL, data is stored in tables with rows and columns, while in an OODBMS like MongoDB, data is stored as documents (objects) that can contain complex data structures.

C/C++ programming concepts#

C and C++ are foundational languages in computer science that form the backbone of many modern programming concepts. Mastering these languages enables developers to write efficient, high-performance software and provides a solid understanding of deeper programming principles often explored in IBM technical interview questions.

19. What’s the difference between function overloading and function overriding in C++?

• Function overloading: In overloaded functions, multiple functions can have the same name but different parameters. For example, a function add(int a, int b) and another add(double a, double b) can coexist.

• Function overriding: A derived class can provide a specific implementation of a base class method for overridden functions. For example, if a base class has a void draw() method; a derived class can implement its version of void draw().

20. What is inheritance in C++?
    It allows a class to inherit properties and behaviors from another class. It promotes code reusability and reduces redundancy in the code. If you have a base class Vehicle with common properties like speed and methods like start(), a derived class Car can inherit these attributes and add specific ones like numberOfDoors. This way, Car reuses the functionality from Vehicle without redundant code.
    

21. What are the various types of storage classes in C?

• Auto: It is the default storage class for local variables.

• Static: It preserves the variable’s value between multiple calls to the same function.

• Extern: It allows variables to be shared between files.

• Register: It allows the compiler to use a CPU register for faster access.

22. What’s the difference between dangling, void, null, and wild pointers?

• Dangling pointer: A dangling pointer points to a memory location that has been freed.

• Void pointer: A generic pointer can point to any data type.

• Null pointer: It points to NULL (zero memory location).

• Wild pointer: It points to an unpredictable memory location.

23. Explain the major concepts of object-oriented programming in the context of C++ programming language.

• Encapsulation: It bundles data and methods in a single unit (class).

• Inheritance: It is a mechanism for a class to inherit features from another class.

• Polymorphism: It is the ability to present the same interface for different data types.

• Abstraction: It hides complex implementation details.

24. Differentiate between struct and union in the context of C programming language.

• Struct: It groups multiple data types. For example, struct Person { char name[20]; int age; }; can store both name and age.

• Union: It saves memory by storing different data types in the same memory location. For example, union Data { int intValue; float floatValue; }; can store either an integer or a float but not both simultaneously.

Data structures and algorithms (DSA)#

A strong understanding of data structures and algorithms is essential for solving complex problems efficiently and is highly valued in technical roles. Mastering these concepts helps developers optimize their code and improve application performance and is also one of the top IBM interview tips for excelling in technical assessments.

25. What are the different types of data structures, and when should each be used?

• Arrays: The arrays store elements in contiguous memory and are ideal for static data with known size.

• Linked lists: These allow dynamic memory allocation and are suitable when frequent insertions or deletions are needed.

• Stacks and queues: These follow last in, first out (LIFO), and first in, first out (FIFO) principles, respectively, and are used in algorithms like depth-first and breadth-first searches.

• Trees: Trees are a hierarchical structure representing relationships, like file systems or organizational charts.

• Graphs: These are useful for representing networks and connections, such as social networks and transportation systems.

• Hash tables: They enable fast access to data with a unique key and are commonly used in caching and indexing.

26. What’s the difference between queue and deque?

• Queue: It follows the FIFO (first in, first out) order. The enqueue operations add items at the back, and dequeue operations remove from the front.

• Deque (double-ended queue): It allows insertion and deletion at both ends. We can add and remove items from the front and back, making it more flexible.

27. Write a program to find the maximum depth or height of a given binary tree. Given a binary tree, write a function to find its maximum depth. The maximum depth is defined as the number of nodes along the longest path from the root node down to the farthest leaf node.

• Solution essence: A recursive approach is suitable for finding the maximum depth of a binary tree. The idea is to calculate the height of the left and right subtrees for every node. The maximum depth at any node is determined by taking the maximum left and right subtree depths and adding 1 to account for the current node. The base case occurs when the node is null and a depth of 0 is returned. Recursively, this will provide the depth of the entire tree when called on the root.

28. Write a program to print all the anagrams together.
    Given an array of strings, group the strings that are anagrams of each other. An anagram is a word or phrase formed by rearranging the letters of another.

• Solution essence: To solve this problem, you can use a hash map (or dictionary) to group words that are anagrams. The key idea is to sort the characters of each string, as two anagrams will produce the same sorted string. Use the sorted string as the key in the hash map, and append the original string to the list of values for that key. After processing all strings, the values in the hash map will represent groups of anagrams, which can then be returned as the result.

29. Write a program to find the maximum product subarray.
    Given an integer array, find the contiguous subarray with the largest product within the array. The array may contain both positive and negative numbers.

• Solution essence: The key to solving this problem is to track both the maximum and minimum products at each position because multiplying a negative number by a previously small negative number can result in a large positive number. Iterate through the array and, at each step, calculate the maximum and minimum products by considering the current element and the products of the current element with the previous maximum and minimum. Update the global maximum product whenever the current maximum exceeds it. Finally, return the global maximum product after completing the iteration.
  

30. What are the various types of sorting algorithms?

    1. Bubble sort: It repeatedly swaps adjacent elements if they are in the wrong order. It’s simple but inefficient for large datasets with a time complexity of $O(n^2)$.

    2. Selection sort: It divides the array into a sorted and unsorted part. Repeatedly selects the smallest element from the unsorted part and swaps it with the first unsorted element. Its time complexity is also $O(n^2)$.

    3. Insertion sort: It builds the sorted array one element at a time by comparing the current element with those in the sorted part and inserting it into the correct position. It’s efficient for small or nearly sorted arrays with a time complexity of $O(n^2)$.

    4. Merge sort: A divide-and-conquer algorithm splits the array into two halves, recursively sorts each half, and then merges the two sorted halves. It has a time complexity of $O(n log n)$ and is stable.

    5. Quick sort: It is also a divide-and-conquer algorithm that selects a ‘pivot’ element and partitions the array such that elements smaller than the pivot come before it and elements greater than the pivot come after it. It has an average-case time complexity of $O(n log n)$ but degrades to $O(n^2)$ in the worst case if the pivot selection is poor.

    6. Heap sort: It converts the array into a binary heap structure and repeatedly extracts the maximum element to build a sorted array. It has a time complexity of $O(n log n)$.

    7. Radix sort: A non-comparative sorting algorithm sorts numbers digit by digit, from the least significant to the most significant. It’s efficient for fixed-length integer sorting with a time complexity of $O(nk)$, where $k$ is the number of digits.

    8. Bucket sort: It distributes elements into buckets and sorts each bucket individually, usually using another sorting algorithm like insertion sort. It works best for uniformly distributed data with time complexity $O(n + k)$, where $k$ is the number of buckets.

Resources to prepare#

To effectively prepare for the coding portion of IBM’s interview, consider leveraging some of the most popular resources from Educative as follows:

You may consider the following course to enhance your C++ skills based on your experience:

To prepare for the operating system and object-oriented design and analysis, the following are well-suited courses:

Good luck with your preparation!