ITEC 2211 C191 Operating Systems for Programmers

Correct Answer

A. Device driver

Explanation

 In a microkernel architecture, the essential functions are kept minimal and are typically limited to interprocess communication (IPC), address spaces, and scheduling. The goal of a microkernel is to run only the core services within the kernel, with other functionalities such as device drivers, file systems, and network protocols being managed by user-space servers or modules. This design allows for greater modularity, easier maintenance, and increased security by reducing the complexity of the kernel itself. Device drivers, which interact directly with hardware, are usually implemented outside the microkernel.

Why other options are wrong

B. Interprocess communication (IPC)

This is incorrect because IPC is a crucial function in a microkernel architecture. IPC allows processes to communicate with each other, which is essential for the functioning of the system, especially in a microkernel design where non-kernel components need to interact with each other.

C. Address spaces

This is incorrect because managing address spaces is a core function of a microkernel. Address spaces are used to provide memory isolation for processes, ensuring that one process cannot directly interfere with the memory of another, which is a critical aspect of system security and stability.

D. Scheduling

This is incorrect because process scheduling is also an essential function of a microkernel. It determines the order in which processes are executed, ensuring fair and efficient use of system resources. In a microkernel design, scheduling is typically a core function of the kernel, enabling the management of multiple processes in an efficient manner.

Correct Answer

B. The OS programs a timer to interrupt the CPU at a future time

Explanation

The operating system can regain control of the CPU from a user process by programming a timer to trigger an interrupt at a set interval. This is known as a time-sharing mechanism, and it ensures that no single process can monopolize the CPU. This technique is part of process scheduling, and it is the basis of preemptive multitasking, which is used in modern operating systems. When the timer interrupt occurs, the OS can stop the user process and take control to perform necessary tasks, such as running other processes or managing resources.

Why other options are wrong

A. The user process does I/O

This option is incorrect because while I/O operations may cause the process to yield the CPU, they do not guarantee periodic regaining of control by the OS. I/O waits can also block the process, so the OS might not regain control if the process is not performing I/O.

C. The user process performs a system call

This option is incorrect because system calls are invoked by the user process when it needs services from the operating system. While a system call does transfer control to the OS, it doesn't guarantee periodic control over the CPU. The OS must intervene periodically through mechanisms like timer interrupts, not just system calls.

D. The user process runs at a lower privilege level

This option is incorrect because the privilege level of a process does not determine how often the OS regains control. The OS can run in higher privilege levels, but it still needs mechanisms like interrupts to periodically regain control.

E. The OS runs at a higher privilege level

This option is incorrect because although the OS runs at a higher privilege level (kernel mode), this alone does not guarantee periodic control of the CPU. The timer interrupt mechanism, as described in the correct answer, is required to periodically regain control.

Correct Answer

 B. They facilitate communication between the program and hardware devices.

Explanation

Input/Output (I/O) operations are a critical part of how an operating system facilitates interaction between a program and external devices (like storage devices, printers, displays, and network interfaces). I/O operations allow the program to receive inputs (e.g., data from a keyboard, mouse, or file) and provide outputs (e.g., display on screen, writing to a file). Without I/O operations, programs would be isolated from interacting with the real world, making them unable to process or produce meaningful data.

Why other options are wrong

A. They allow programs to run without any external data.

This option is incorrect because I/O operations are responsible for providing the external data to programs. Without I/O, programs would not be able to interact with external systems or data sources.

C. They manage the allocation of CPU time to processes.

This option is incorrect because managing CPU time is the responsibility of the operating system’s process scheduler, not I/O operations. I/O operations handle interactions with devices but do not manage CPU time.

D. They are responsible for the security of the operating system.

This option is incorrect because security is typically managed by other components of the operating system, such as user authentication mechanisms, access control lists, and the kernel. I/O operations focus on data transfer between programs and devices rather than on security management.

Correct Answer

D. gathers together multiple CPUs to accomplish computational work.

Explanation

A clustered system is designed to combine multiple CPUs, often across multiple machines, to work together as a unified system. This allows for increased computational power and reliability, as tasks can be distributed across the cluster to improve performance. In case of a failure in one part of the system, other parts can take over, ensuring continuous operation and scalability.

Why other options are wrong

A. is used when the right time requirements are present

This option is incorrect because clustered systems are not specifically used only for time-sensitive requirements. While they can handle high-performance or real-time tasks, their primary function is to combine multiple systems for enhanced computational power and fault tolerance.

B. generally cannot provide services if one or more systems in the cluster fail.

This option is incorrect because clustered systems are designed for redundancy and fault tolerance. If one system in the cluster fails, other systems can continue to provide services, ensuring high availability and minimizing downtime.

C. can only operate on one application at a time

This option is incorrect because clustered systems are designed to handle multiple applications simultaneously. They can distribute workloads across multiple nodes, allowing them to run more than one application or task at a time.

Correct Answer

A. changes the protection bits associated with a file.

Explanation

The chmod system call is used to change the file permissions (protection bits) of a file or directory. These permissions determine who can read, write, or execute the file. The protection bits are important for managing file security and ensuring that only authorized users can perform certain actions on files. chmod modifies these bits to control access to the file or directory.

Why other options are wrong

B. changes the mode associated with a terminal (raw, cbreak, or cooked).

This is incorrect because the chmod system call is specifically for changing file permissions, not terminal modes. Terminal modes, such as raw, cbreak, or cooked, control how input is processed, and are managed by other system calls, such as tcsetattr or stty.

C. changes the base of the numbers used with the mod function.

This is incorrect because the chmod system call does not affect mathematical operations like the mod function or change the base of numbers. It specifically works with file permissions, not mathematical calculations or data transformations.

Correct Answer

C. It changes the current position for reading or writing in a file.

Explanation

The reposition() function, or similar functions like seek() or lseek() in various programming languages, changes the current position of the file pointer within an open file. This is crucial for scenarios where you want to move to a specific location in the file to read from or write to a particular section. It allows for non-sequential file operations, where you can jump to different parts of the file rather than reading or writing linearly from start to finish. This is particularly useful for random access to large files or for updating specific parts of a file without rewriting the entire content.

Why other options are wrong

A. It closes a file descriptor.

This option is incorrect because closing a file descriptor is a different operation entirely, typically done using functions like close(). The reposition() function does not handle file closing; it only adjusts the read/write pointer position within the file.

B. It reads data from a file.

This is incorrect because the reposition function does not read data from a file. It only adjusts the pointer to a new location in the file. The actual reading of data is typically done with functions like read() or fread() after repositioning.

D. It creates a new file.

This is incorrect because creating a new file is done using different functions such as open() or fopen() with the appropriate flags. The reposition function is not involved in file creation.

Correct Answer

 B. debugger

Explanation

 A debugger is a tool used to analyze memory dumps, examine the state of a program at various points during execution, and identify issues such as memory leaks, invalid memory access, or logical errors. When a program crashes or terminates unexpectedly, a memory dump can be captured, and the debugger allows developers to investigate what caused the termination. By stepping through the program's execution and inspecting memory contents, a debugger helps identify and fix bugs in the software.

Why other options are wrong

A. profiler

A profiler is a tool used to analyze the performance of a program, such as identifying performance bottlenecks or inefficient code. It does not specifically analyze memory dumps to identify issues related to program termination.

C. compiler

A compiler translates source code written in a high-level programming language into machine code. It does not analyze memory dumps or help with debugging program execution after a crash.

D. interpreter

An interpreter executes programs directly, often translating high-level code line by line at runtime. While it can be used for debugging, it is not specifically designed to analyze memory dumps from terminated programs like a debugger is.

Correct Answer

B. To change file permissions

Explanation

The chmod (change mode) command in UNIX and Linux operating systems is used to modify the permissions of files and directories. It allows users to specify who can read, write, or execute a file. Permissions are set for the file owner, group members, and others. This command is essential for managing access control in multi-user environments, ensuring that only authorized users can access or modify files.

Why other options are wrong

A. To change file ownership

This option is incorrect because the chmod command does not change file ownership. The command used to change file ownership is chown. chmod only affects the permissions associated with a file, not its ownership.

C. To create new directories

This option is incorrect because the chmod command does not create new directories. The command used for creating new directories is mkdir. chmod is solely for modifying file permissions.

D. To delete files

This option is incorrect because the chmod command does not delete files. The command used to delete files is rm. chmod is focused on changing file permissions, not file removal.

Correct Answer

B. Use ReadFile() in a loop to read smaller segments of the file.

Explanation

When dealing with large files, it's crucial to avoid memory overflow by reading the file in smaller chunks. Using the ReadFile() system call in a loop allows the program to read parts of the file into memory at a time, thus managing memory more efficiently. This approach prevents the program from trying to load the entire file into memory, which can lead to overflow or excessive memory consumption. By processing the file in manageable chunks, the program can also handle larger files even if the available memory is limited.

Why other options are wrong

A. Read the entire file at once into memory.

This is incorrect because reading the entire file at once can easily cause memory overflow, especially with large files. If the file is too large to fit into memory all at once, this approach could lead to crashes or inefficient memory usage. It's better to read the file in smaller, more manageable chunks.

C. ReadFile() should not be used for large files.

This option is incorrect because the ReadFile() system call can indeed be used for large files. The issue isn't the ReadFile() function itself but how the file is managed in memory. With proper chunking, ReadFile() can be used efficiently to handle large files without causing memory overflow.

D. Open the file in write mode before reading.

This option is incorrect because opening a file in write mode before reading it is unnecessary and may even cause issues. For reading a file, the file should be opened in read mode. Write mode allows for modifications to the file, which is not needed when the goal is simply to read the file in chunks to prevent memory overflow.