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OS · Question Set
OS Introduction interview questions for placements and exams.
Questions
12
Included in this set
Subject
OS
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for OS.
Operating systems can be classified by how they manage tasks: batch, time-sharing, real-time, etc. A batch operating system schedules jobs without manual intervention.
For complete preparation, combine this set with full subject-wise practice for OS. You can also explore other subjects and sets from the links below.
A process is an independent program in execution. It has its own memory space, resources, address space. A thread is a smaller unit of execution within a process. Threads share the same address space and resources of their parent process but have their own program counter and stack. Using threads is lighter weight, faster to switch between, and useful for concurrency inside a process, but you must handle synchronization carefully.
Typical process states are running (using CPU), ready (waiting for CPU), waiting or blocked (waiting for I O or event). "Interrupted" is not normally listed as a standard state in the lifecycle model.
A system call is the mechanism by which a user program requests a service from the kernel of the operating system. It allows safe transition from user mode to kernel mode to execute privileged operations like file I O, process control or creating threads. It is important because it enforces protection, isolates user code from kernel code, and enables resource management.
In a time-sharing system the CPU switches among many users’ interactive tasks rapidly, giving the illusion that each user has their own machine. The OS allocates short time slices to tasks and context switches quickly. It improves responsiveness for many users.
IPC mechanisms include message passing, shared memory, pipes, sockets etc. Virtual memory is a memory management technique, not a communication mechanism between processes.
A PCB is a data structure used by the OS to keep track of each process. It stores process identifier (PID), process state, program counter, register values, memory limits, list of open files, scheduling information and more. The OS uses the PCB to resume and manage processes.
The bootstrap program is the initial code run when a machine starts (after BIOS or firmware). It loads the operating system kernel into memory and starts execution of the OS.
A zombie process is a process that has finished execution (exit) but still has an entry in the process table because its parent has not yet read its exit status (via wait). It arises when the child ends but the parent hasn’t yet called wait, so the OS cannot release the PCB until the parent does so.
The operating system acts as the intermediary between hardware and application software. It manages resources like CPU, memory, and I O so applications can run efficiently and correctly.
The kernel is the heart of the OS. It handles resource management, process scheduling, memory control, device I O and communication between hardware and software.
Multiprogramming is the technique where the OS keeps multiple programs in memory and switches between them so the CPU is busy when one program waits for I O. It improves utilization of the CPU.