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Prepare top Operating System interview questions with answers covering processes, threads, scheduling, synchronization, deadlock, memory management, paging, segmentation, and virtual memory. Use this page as a focused learning resource for operating systems concepts, interview preparation, and practical revision.
Operating System is one of the highest-value core subjects for interviews because it connects software behavior with system resources. If DBMS explains data and Computer Networks explains communication, Operating System explains how programs actually run inside a machine.
This page is for fast placement revision and viva-style answers.
An operating system is system software that manages hardware resources and provides services for application programs and users.
Main functions:
The main goal is to make computer hardware easy and efficient to use.
The kernel is the core part of the operating system that directly manages CPU, memory, and devices. The operating system is the broader system that includes kernel plus utilities and interfaces.
A process is a program in execution. It has its own memory, state, program counter, and required resources.
A thread is the smallest unit of CPU execution inside a process. Multiple threads of the same process can share memory and resources.
PCB stands for Process Control Block. It stores information about a process such as:
Common process states:
CPU scheduling is the method used by the operating system to decide which process should use the CPU next.
Context switching is the process of saving the state of one process and loading the state of another so CPU execution can switch safely.
Synchronization is the coordination of multiple processes or threads so shared data remains correct and race conditions are avoided.
A critical section is the part of a program where shared data is accessed. Only one process or thread should execute that part at a time in many cases.
A semaphore is a synchronization tool used to control access to shared resources.
A mutex is a locking mechanism that allows only one thread to access a resource at a time.
Deadlock is a condition where two or more processes wait for each other indefinitely and none can proceed.
The four Coffman conditions are:
Starvation happens when a process waits for a very long time because CPU or resources keep getting assigned to other processes.
Memory management is the function of the OS that allocates, tracks, protects, and frees memory for processes.
Paging divides memory into fixed-size blocks called pages and frames. It helps manage memory efficiently and supports virtual memory.
Segmentation divides memory based on logical units such as code, data, and stack.
Virtual memory allows execution of programs larger than physical RAM by using secondary storage as an extension of main memory.
Thrashing happens when the system spends too much time swapping pages in and out of memory and too little time doing actual execution.
OS answers sound better when you explain both concept and purpose. For example, do not only say "paging divides memory." Also say why it is used and what problem it solves.
Processes, threads, scheduling, synchronization, deadlock, memory management, paging, segmentation, and virtual memory are the most important OS interview topics.
Operating System shows whether a candidate understands how programs run, share resources, use memory, and interact with hardware, which is important in software and systems interviews.
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