Computer Science MCQS

Device drivers present a uniform device-access interface to the I/O subsystem.

They act as a bridge between the operating system and hardware devices, providing a standardized way for applications to interact with different types of devices. This abstraction layer simplifies the development of applications and makes the I/O subsystem more manageable.

frame table is a data structure used by the operating system to keep track of physical memory frames. It contains information about the status of each frame, such as whether it's free or allocated to a process, and if allocated, which page is currently stored in it. This information is crucial for memory management and page replacement algorithms.

b) changes

Transient code is temporary code that is loaded into memory only when needed and then removed. As a result, the size of the operating system changes during program execution. It increases when the transient code is loaded and decreases when it is removed.

every address generated by the CPU is being checked against the relocation and limit registers

This is the correct answer.

Relocation register: Holds the base address of a process's memory space.

Limit register: Specifies the maximum size of a process's memory space.

Whenever a process generates an address, the CPU checks it against these registers. If the address is within the process's allowed memory range, it's valid. Otherwise, it's considered an invalid access and is prevented. This mechanism protects the operating system and other processes from being corrupted by a rogue process.

This protection is essential for maintaining system integrity and security.

c) operating system

The main memory primarily accommodates the operating system. It stores the core components of the OS, which are essential for managing the computer's resources and controlling its operations. While user processes and parts of the CPU (registers, cache) also reside in memory, the operating system is the primary occupant and manager of main memory.

a) must never

Swapping a process with pending I/O or one that is executing I/O operations into operating system buffers is not advisable because:

Inconsistency: If a process is swapped out while waiting for I/O, the I/O completion might occur while the process is not in memory. This can lead to data inconsistency.

Overhead: Continuously swapping processes in and out due to I/O operations can introduce significant overhead, impacting system performance.

To avoid these issues, operating systems typically employ techniques like buffering or double buffering to handle I/O operations without requiring process swapping.

This means it looks at the current allocation of resources to processes and the maximum resource needs of each process to determine if granting a resource request would lead to a deadlock. By analyzing this information, the algorithm can prevent deadlock by denying requests that could potentially create a circular wait.

The Banker's Algorithm is a classic example of a deadlock avoidance algorithm.

Checking for deadlock every time a resource request is made is the most effective approach.

This is because:

Early detection: It allows for immediate identification of potential deadlocks, preventing them from escalating.

Resource optimization: By detecting deadlocks early, the system can take corrective actions, such as process termination or resource preemption, to avoid system-wide issues.

Efficient resource utilization: Continuously monitoring resource requests helps in optimizing resource allocation and preventing deadlocks.

While checking at fixed intervals might be less computationally expensive, it increases the risk of missing deadlock conditions, especially if the interval is too long.

Therefore, checking for deadlock at every resource request offers the best balance between efficiency and deadlock prevention.

FCFS (First Come First Served) is particularly troublesome for time-sharing systems.

In time-sharing systems, multiple users share the CPU, and each user expects a quick response. FCFS, where processes are executed in the order they arrive, can lead to long wait times for users whose processes are behind long-running ones. This results in poor responsiveness and user dissatisfaction.

To address this, time-sharing systems typically use scheduling algorithms like Round Robin or Priority scheduling, which provide better fairness and responsiveness.