Topic in Operating Systems
An operating system is system software that manages a computer's hardware and provides common services, such as memory, files and I/O, to application programs. Introductory questions check whether you can separate the kernel from user programs, tell user mode from kernel mode, and explain why system calls exist. You should also be able to compare batch, time-sharing, distributed and real-time systems, including the difference between hard and soft real-time deadlines. Other favourites include multiprogramming versus multitasking, interrupts and traps, the bootstrap process, symmetric versus asymmetric multiprocessing, NUMA memory access costs, and the role of hardware such as the Trusted Platform Module.
Below are 30 practice questions from a pool of 210 Introduction to OS MCQs, one of 12 topics in Operating Systems. Each shows the correct answer with an explanation; when you are ready, take a timed quiz to test recall under exam conditions.
Each question below shows the correct answer with a full explanation. Use these to build conceptual understanding before attempting a timed quiz.
Q1. What is an operating system?
An operating system is system software that manages computer hardware and software resources and provides common services for computer programs.
Q2. Which of the following is NOT a function of an operating system?
Compiling user programs is the function of a compiler, not the operating system. The OS manages memory, processes, and files.
Q3. Which of the following is an example of a mobile operating system?
Android is a mobile operating system developed by Google, primarily used in smartphones and tablets.
Q4. What does the term 'booting' mean in the context of operating systems?
Booting is the process of loading the operating system from secondary storage into the main memory (RAM) when the computer is started.
Q5. In a batch operating system, jobs are processed:
In a batch operating system, similar jobs are grouped together into batches and processed sequentially without user interaction.
Q6. Which type of operating system allows multiple users to use the computer simultaneously?
A time-sharing (multitasking) OS allows multiple users to share computer resources simultaneously by rapidly switching between tasks.
Q7. The interface between the user and the operating system is called:
The shell is the interface between the user and the operating system. It can be a command-line interface (CLI) or graphical user interface (GUI).
Q8. Which of the following is a real-time operating system characteristic?
A real-time operating system (RTOS) guarantees that operations are completed within strict time constraints, which is critical for systems like air traffic control.
Q9. UNIX was originally developed at:
UNIX was originally developed at AT&T Bell Labs by Ken Thompson and Dennis Ritchie in the early 1970s.
Q10. The core component of an operating system is called the:
The kernel is the core component of an operating system that manages system resources and provides the lowest-level abstraction layer for hardware.
Q11. What is the difference between multiprogramming and multitasking?
Multiprogramming keeps multiple jobs in memory to keep the CPU busy. Multitasking extends this with time-sharing, allowing interactive user sessions by rapidly switching between tasks.
Q12. What is a system call?
A system call is a programmatic way for a process to request a service from the operating system's kernel, acting as the interface between user programs and the OS.
Q13. Which mode of CPU operation has unrestricted access to all hardware resources?
Kernel mode (also called supervisor or privileged mode) has unrestricted access to all hardware resources. User mode has limited access for protection.
Q14. What is the purpose of the mode bit in the CPU?
The mode bit is used to distinguish between user mode (mode bit = 1) and kernel mode (mode bit = 0) to ensure proper protection of system resources.
Q15. Spooling in operating systems refers to:
SPOOL (Simultaneous Peripheral Operations On-Line) is a technique where data is temporarily held in a buffer to be used by a slower device, overlapping I/O with computation.
Q16. An interrupt is:
An interrupt is a signal to the processor indicating that an event needs immediate attention, causing the CPU to pause current execution and handle the interrupt.
Q17. What is the difference between a trap and an interrupt?
A trap (or exception) is a software-generated interrupt caused by an error or a user program request, while an interrupt is typically generated by hardware devices.
Q18. DMA (Direct Memory Access) is used to:
DMA allows certain hardware subsystems to access main system memory independently of the CPU, freeing the CPU from handling every byte of data transfer.
Q19. A distributed operating system:
A distributed OS manages a group of distinct computers and makes them appear to be a single computer, enabling resource sharing and load distribution.
Q20. What is the bootstrap program?
The bootstrap program (stored in ROM/firmware) is the first program to run when a computer is powered on. It initializes hardware and loads the operating system kernel into memory.
Q21. In the context of OS design, what is the key advantage of a microkernel architecture over a monolithic kernel?
Microkernels run most OS services in user space, which improves reliability (a service crash doesn't crash the kernel) and extensibility, though at the cost of some performance overhead.
Q22. What is the purpose of a hypervisor in virtualization?
A hypervisor (Virtual Machine Monitor) creates and manages virtual machines, providing an abstraction layer that allows multiple guest operating systems to share physical hardware.
Q23. What distinguishes a Type 1 hypervisor from a Type 2 hypervisor?
A Type 1 (bare-metal) hypervisor runs directly on hardware (e.g., VMware ESXi), while a Type 2 (hosted) hypervisor runs on top of a conventional host OS (e.g., VirtualBox).
Q24. In a hard real-time system, what happens when a deadline is missed?
In a hard real-time system, missing a deadline is considered a total system failure. These systems guarantee that critical real-time tasks complete on time (e.g., airbag deployment systems).
Q25. What is the main purpose of the interrupt vector table?
The interrupt vector table contains the addresses of interrupt service routines (ISR). When an interrupt occurs, the CPU uses this table to find and execute the appropriate handler.
Q26. What is the concept of 'dual-mode operation' in operating systems and why is it essential?
Dual-mode operation separates user mode and kernel mode execution, preventing user programs from directly accessing hardware or OS data structures, which is essential for system protection and stability.
Q27. In clustered systems, what is the difference between asymmetric clustering and symmetric clustering?
In asymmetric clustering, one machine is on hot-standby mode monitoring the active server. In symmetric clustering, all nodes run applications and monitor each other, providing better resource utilization.
Q28. What mechanism does the OS use to prevent a user program from running indefinitely and never returning control?
The OS uses a timer interrupt that fires after a set interval to ensure that no user program can monopolize the CPU. When the timer expires, control returns to the OS for scheduling decisions.
Q29. What is the purpose of caching in the memory hierarchy of an operating system?
Caching stores copies of frequently accessed data in faster storage (like CPU cache or RAM) to reduce the average time to access data, exploiting the principle of locality.
Q30. What problem does cache coherency address in multiprocessor systems?
Cache coherency ensures that when one processor updates data in its local cache, the change is propagated to all other caches holding copies of that data, maintaining data consistency across processors.
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