Yokogawa Senior Systems Engineer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

This round started with some questions from Programmable Logic Controllers or PLC followed by some basic questions from Intel 8051 Microcontroller.

Q1. What are the general functions of a Programmable Logic Controller (PLC)?
Ans. 
PLCs are used to control machinery and automate processes in industrial settings.
• Monitoring inputs from sensors

• Executing control algorithms

• Communicating with other devices

• Logging data for analysis

• Implementing safety functions

• Examples: controlling a conveyor belt, regulating temperature in a furnace
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Q2. Can you describe the basic elements in Ladder logic programming?
Ans. 
Ladder logic programming is a graphical programming language used for PLCs, with basic elements like contacts, coils, timers, and counters.
• Ladder logic consists of rungs, which are made up of inputs (contacts) and outputs (coils).

• Contacts represent conditions that must be met for the output to be energized.

• Coils are outputs that are energized when the conditions of the contacts are met.

• Timers and counters are used to c...read more
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Q3. What are the different types of PLC inputs and outputs?
Ans. 
PLC inputs and outputs include digital inputs, digital outputs, analog inputs, and analog outputs.
• Digital inputs: used for receiving binary signals (on/off, high/low). Examples: push buttons, limit switches.

• Digital outputs: used for sending binary signals. Examples: relays, solenoids.

• Analog inputs: used for receiving continuous signals. Examples: temperature sensors, pressure transducers.

• Analog outputs: used for sendin...read more
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Q4. What are the advantages and disadvantages of the S7 controller?
Ans. 
The S7 controller offers high performance and flexibility but can be complex to program and expensive.
• Advantages: high performance, flexibility, scalability

• Disadvantages: complexity in programming, expensive

• Example: S7-1200 offers fast processing speeds and can be easily expanded with additional modules

• Example: Programming for S7 controllers may require specialized training and expertise
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Q5. Can you explain the time stamp available in the S7-200 PLC?
Ans. 
The time stamp in S7-200 PLC is used to record the time when a specific event occurs.
• Time stamp is a feature in S7-200 PLC that records the time when a specific event happens.

• It helps in tracking the sequence of events and troubleshooting issues.

• Time stamp can be used to monitor the performance of the PLC system.

• Example: A time stamp can be recorded when a sensor detects a change in temperature.

• Example: Time stamp can ...read more
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Q6. Could you explain Jnc in the context of microcontrollers?
Ans. 
Jnc stands for Jump and Call in the context of microcontrollers.
• Jnc is an instruction used in microcontrollers to jump to a specified address if the carry flag is not set.

• It is commonly used in conditional branching operations in microcontroller programming.

• For example, in 8051 microcontroller assembly language, the instruction JNC label will jump to the specified label if the carry flag is not set.
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Q7. What are the types of interrupts in the Intel 8051 microcontroller?
Ans. 
The types of interrupts in the Intel 8051 microcontroller include external hardware interrupts, timer interrupts, and serial communication interrupts.
• External hardware interrupts are triggered by external devices connected to the microcontroller.

• Timer interrupts are generated by the internal timers of the microcontroller.

• Serial communication interrupts occur when data is received or transmitted through the serial port.

• ...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This round was heavily inclined towards Operating System and Computer Networks and the interviewer asked questions revolving around the fundamentals of the subject.

Q1. What is a bootstrap program in an operating system?
Ans. 
A bootstrap program is a small program that initializes the operating system on a computer.
• Bootstrap program is stored in ROM or EEPROM and is executed when the computer is powered on.

• It loads the operating system kernel into memory and starts its execution.

• Bootstrap program is responsible for setting up the initial state of the operating system.

• Examples include BIOS (Basic Input/Output System) in PCs and UEFI (Unified
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Q2. Can you explain demand paging?
Ans. 
Demand paging is a memory management scheme where pages are only brought into memory when they are demanded by the program.
• Pages are loaded into memory only when needed

• Helps in reducing the amount of physical memory required

• Improves overall system performance by allowing more processes to run simultaneously

• Commonly used in virtual memory systems
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Q3. Can you explain any 5 essential UNIX commands?
Ans. 
Five essential UNIX commands are ls, cd, pwd, mkdir, and rm.
• ls - list directory contents

• cd - change directory

• pwd - print working directory

• mkdir - make directory

• rm - remove files or directories
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Q4. What are the different types of VPN?
Ans. 
Different types of VPN include remote access VPN, site-to-site VPN, and client-to-site VPN.
• Remote access VPN allows individual users to connect to a private network from a remote location.

• Site-to-site VPN connects entire networks together over the internet.

• Client-to-site VPN allows individual devices to connect to a private network.

• Examples include OpenVPN, IPsec, and SSL VPN.
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Q5. Can you describe the OSI Reference Model?
Ans. 
The OSI Reference Model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven layers.
• The OSI Reference Model stands for Open Systems Interconnection Reference Model.

• It consists of seven layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

• Each layer has specific functions and communicates with the adjacent layers for data trans...read more
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Q6. Can you explain the TCP and UDP protocols?
Ans. 
TCP is a connection-oriented protocol that ensures reliable data delivery, while UDP is a connectionless protocol that focuses on speed.
• TCP stands for Transmission Control Protocol and is used for reliable data transmission.

• TCP establishes a connection between sender and receiver before data transfer.

• TCP uses sequencing and acknowledgment to ensure data integrity.

• UDP stands for User Datagram Protocol and is used for fa...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my
role.

Q1. What is something about you that is not included in your resume?
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Round duration - 60 Minutes
Round difficulty - Medium

This round started with 1 coding question related to Prime Numbers in which I was first asked to explain my approach and then write the pseudo code for it. This was followed by some preety standard questions from OOPS and Java.

Q1. 
Nth Prime Number Problem Statement
Find the Nth prime number given a number N.
Explanation:
A prime number is greater than 1 and is not the product of two smaller natural numbers. A prime number has exa...read more
Ans. 
To find the Nth prime number given a number N, implement a function that returns the Nth prime number.
• Create a function that takes N as input and returns the Nth prime number.

• Use a loop to iterate through numbers and check if they are prime.

• Keep track of the count of prime numbers found until reaching N.

• Optimize the algorithm by checking only up to the square root of the number for primality.

• Example: For N = 7, the 7th
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Q2. What is the difference between an abstract class and an interface in OOP?
Ans. 
Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructors, fields, and methods, while interface cannot.

• A class can implement multiple interfaces but can only inherit from one abstract class.

• Abstract classes are used to define a common base class for related classes, while interfaces define a contract for classes to implement.

• Examp...read more
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Q3. What is the garbage collector in Java?
Ans. 
Garbage collector in Java is a built-in mechanism that automatically manages memory by reclaiming unused objects.
• Garbage collector runs in the background to reclaim memory from objects that are no longer in use.

• It helps prevent memory leaks and optimize memory usage.

• Examples of garbage collectors in Java include Serial, Parallel, CMS, and G1.
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Q4. What is meant by exception handling?
Ans. 
Exception handling is a programming concept where errors or exceptional events are dealt with in a structured manner.
• Exception handling allows for graceful handling of errors in a program.

• It involves using try, catch, and finally blocks to manage exceptions.

• Examples include catching divide by zero errors or file not found exceptions.
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Q5. How does ConcurrentHashMap work in Java?
Ans. 
ConcurrentHashMap is a thread-safe implementation of the Map interface in Java.
• ConcurrentHashMap allows multiple threads to read and write to the map concurrently without the need for external synchronization.

• It achieves thread-safety by dividing the map into segments, each of which can be locked independently.

• ConcurrentHashMap uses a combination of synchronized blocks and volatile variables to ensure thread-safety.

• It ...read more
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Round duration - 50 Minutes
Round difficulty - Medium

This round had 1 coding question related to LRU Cache where I had to code its implementation in a production-ready manner explaining my overall approach with proper complexity analysis. This was followed by some Mutithreading questions from Java and then at last the interviewer asked me some basic design patterns in Software Engineering and some more questions related to OOPS.

Q1. 
LRU Cache Design Question
Design a data structure for a Least Recently Used (LRU) cache that supports the following operations:
1. get(key) - Return the value of the key if it exists in the cache; otherw...read more
Ans. 
Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.
• Implement a doubly linked list to keep track of the order of keys based on their recent usage.

• Use a hashmap to store key-value pairs for quick access.

• When capacity is reached, evict the least recently used item before inserting a new item.

• Update the order of keys in the linked list whenever a key is acc
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Q2. What are the start() and run() methods of the Thread class?
Ans. 
The start() method is used to start a new thread, while the run() method contains the code that will be executed by the thread.
• start() method is used to start a new thread and calls the run() method.

• run() method contains the code that will be executed by the thread.

• Calling run() directly will not create a new thread, it will just execute the code in the current thread.
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Q3. What is a BlockingQueue in the context of multithreading?
Ans. 
BlockingQueue is a thread-safe queue that supports operations that wait for the queue to become non-empty when retrieving an element.
• BlockingQueue is part of the java.util.concurrent package in Java.

• It is used to implement producer-consumer scenarios in multithreaded applications.

• Operations like put() and take() are blocking, meaning they will wait until the queue is in a valid state to perform the operation.

• Example: L
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Q4. What is thread starvation?
Ans. 
Thread starvation occurs when a thread is unable to access the CPU resources it needs to execute its tasks.
• Occurs when a thread is constantly preempted by higher priority threads, preventing it from running

• Can lead to performance degradation and delays in task completion

• Can be mitigated by adjusting thread priorities or implementing thread pooling
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Q5. What is a thread scheduler and how does time slicing work?
Ans. 
A thread scheduler is responsible for managing the execution of multiple threads in a system. Time slicing is a technique used by the scheduler to allocate CPU time to each thread.
• Thread scheduler is a component of the operating system that decides which thread to run next

• Time slicing involves dividing the CPU time among multiple threads based on a predefined time interval

• Example: In a round-robin scheduling algorithm,...read more
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Q6. Can you explain the SOLID principles in Object-Oriented Design?
Ans. 
SOLID principles are a set of five design principles in object-oriented programming to make software more maintainable, flexible, and scalable.
• Single Responsibility Principle (SRP) - A class should have only one reason to change.

• Open/Closed Principle (OCP) - Software entities should be open for extension but closed for modification.

• Liskov Substitution Principle (LSP) - Objects of a superclass should be replaceable with...read more
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Q7. What makes a HashSet different from a TreeSet?
Ans. 
HashSet uses a hash table for storage, while TreeSet uses a red-black tree.
• HashSet provides constant-time performance for basic operations like add, remove, contains.

• TreeSet maintains elements in sorted order, allowing for efficient operations like range queries.

• HashSet does not guarantee any specific order of elements, while TreeSet maintains a sorted order.

• Example: HashSet<String> set = new HashSet<>(); T...read more
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Round duration - 30 Minutes
Round difficulty - Easy

This is a cultural fitment testing round .HR was very frank and asked standard questions. Then we discussed about my role.

Q1. Why should we hire you?
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Q2. Why are you looking for a job change?
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