ITEC 2211 C191 Operating Systems for Programmers

Correct Answer

B. A mechanism for controlling access to resources by users or programs

Explanation

OS protection refers to mechanisms implemented by an operating system to control and restrict access to system resources. This includes files, memory, and other critical resources. The OS uses various techniques, such as access control lists (ACLs) or user authentication, to ensure that only authorized users and programs can access or modify resources. Protection is crucial for maintaining the integrity, confidentiality, and availability of system resources.

Why other options are wrong

A. Activities aimed at ensuring full respect for the rights of the programs or users

While this may be part of an OS's responsibilities, it is not a precise definition of OS protection. OS protection is more specifically concerned with regulating access to system resources rather than merely respecting rights. The focus is on managing resource access and preventing unauthorized actions.

C. Detecting and deterring intrusions from outside

This option describes the role of security or intrusion detection systems, not protection mechanisms within an OS. While OS protection plays a role in securing resources from unauthorized access, detecting and deterring intrusions are tasks typically associated with additional security layers like firewalls, antivirus software, or network monitoring.

D. The act of protecting or the state of being protected

This is a vague description and does not directly address what OS protection entails. OS protection refers specifically to the mechanisms used to control and secure access to system resources. It is a functional process, not just a general description of protection.

Correct Answer

B. Computational power

Explanation

A clustered system enhances computational power by linking multiple computers (or nodes) together to work as a single system. This design helps to distribute computational tasks across multiple machines, increasing processing capacity and providing fault tolerance. By combining resources, such systems can handle larger workloads and execute computations more efficiently compared to a single machine.

Why other options are wrong

A. Data storage capacity

While clustered systems may provide increased data storage by combining resources, their primary focus is on enhancing computational power, not storage capacity. Storage solutions are handled by specific storage technologies like RAID or distributed file systems.

C. User interface design

Clustered systems do not primarily focus on user interface design. Their goal is to improve performance by utilizing multiple computing resources, not to enhance how users interact with the system.

D. Network security

Network security is not the primary focus of clustered systems. Although securing communication between nodes is important, clustered systems are designed mainly to increase computational efficiency rather than to improve network security.

Correct Answer

 A. Standard C library, because it provides the necessary functions for system calls.

Explanation

The Standard C library (libc) in UNIX environments provides a collection of functions that enable interaction with the operating system, including system calls for file management, process control, memory allocation, and other system-level operations. These functions are designed to allow developers to perform actions such as reading and writing files, creating processes, and managing system resources efficiently. System calls are fundamental to interacting with the OS, and the Standard C library is the primary interface for this in a UNIX-based system.

Why other options are wrong

B. OpenGL library, because it handles graphics rendering.

This is incorrect because OpenGL is a graphics library designed for rendering 2D and 3D graphics, not for interacting with the operating system's file management or process control. It is used in applications that require graphics rendering, such as video games or visualizations, but does not provide system call functions.

C. Java library, because it is platform-independent.

This is incorrect because while the Java library provides a platform-independent environment for running programs, it does not directly interact with the operating system's system calls in a way that is native to UNIX. Java provides an abstraction layer that makes it portable across different platforms, but it does not offer direct system call functionalities as provided by the Standard C library.

D. Network library, because it manages network connections.

This is incorrect because the network library is focused on managing network communication and connections, not on general system management tasks like file handling and process management. While useful for applications that require networking functionality, it does not provide the system call functionality needed to manage files and processes within UNIX.

Correct Answer

C. Process control

Explanation

Process control is one of the major categories of system calls in operating systems. These system calls manage the creation, scheduling, execution, and termination of processes. Process control system calls allow the operating system to manage processes, ensure multitasking, and allocate resources efficiently. Examples of process control system calls include fork(), exec(), wait(), and exit().

Why other options are wrong

A. File manipulation

While file manipulation is an important category of system calls (such as open(), read(), write(), and close()), it is not considered one of the major categories like process control, which directly handles the execution and management of processes. File manipulation is a subcategory under the broader category of system calls.

B. Security

While security-related system calls exist (such as setuid() or getuid()), they are typically not categorized as a primary major category of system calls. Security features, such as access control and authentication, are important, but the main categories focus on process control, file manipulation, and communication.

D. Communication

Communication is another critical category, such as inter-process communication (IPC) system calls like pipe(), msgget(), shmget(), etc. However, it is not typically considered one of the major categories as process control encompasses more fundamental operating system functionality related to running programs.

Correct Answer

B. To open an existing file

Explanation

The UNIX open() system call is primarily used to open an existing file for reading, writing, or appending. It provides a file descriptor that can be used by the process to interact with the file. The open() system call can also be used to create a new file if it doesn't already exist, depending on the flags passed to it, but its primary function is to open an existing file.

Why other options are wrong

A. To create a new file

 This option is incorrect because although the open() system call can create a new file if it doesn't exist (with the appropriate flags), its primary purpose is to open a file. It doesn't focus solely on file creation, which is typically done using the creat() system call in earlier UNIX versions or with open() using specific flags.

C. To delete a file

This option is incorrect because the open() system call does not delete files. The system call used to delete a file is unlink() in UNIX and Linux. The open() system call is related to file access, not deletion.

D. To read from a file

This option is incorrect because the open() system call itself does not read from a file. It simply opens the file and returns a file descriptor. To read data from the file, the read() system call is used in conjunction with the file descriptor returned by open().

Correct Answer

 A. Passing the parameter linked list to the system call

Explanation

Passing a parameter linked list to a system call is not a standard method for passing parameters to the operating system. System calls typically pass parameters using simpler methods like registers, memory tables, or the system stack. A linked list is generally not used because it involves more complex memory management and isn't typically efficient for the system call interface.

Why other options are wrong

B. Storing parameters in a table in memory and passing pointer to table in a register

This option is correct because passing parameters by storing them in a table in memory and passing a pointer to that table in a register is a common method. This approach can handle multiple parameters and is efficient for complex system calls.

C. Pushing parameters onto the system stack

This option is correct because pushing parameters onto the system stack is a common technique for passing parameters to a system call. The stack provides an efficient and organized way of managing parameters, especially when multiple parameters need to be passed.

D. Passing parameters in registers

This option is correct because passing parameters in registers is one of the fastest and most common methods. It allows the operating system to quickly access parameters directly from the CPU's registers, minimizing the overhead of other methods.

Correct Answer

B. CloseHandle()

Explanation

The CloseHandle() function is used to close file handles, ensuring that all resources associated with the open file are properly released before the program exits. When a file is opened, the operating system allocates resources like memory and file descriptors to manage that file. Calling CloseHandle() frees these resources and ensures that no file handles are left open, preventing potential memory leaks or resource exhaustion. It is essential for cleanly terminating interactions with files in Windows.

Why other options are wrong

A. OpenFile()

This option is incorrect because OpenFile() is used to open files, not to release resources. It does not perform the cleanup required when closing a file.

C. DeleteFile()

This option is incorrect because DeleteFile() deletes the file from the filesystem, but it does not properly release file handles. It is a separate operation that might be used after closing a file, but not for closing or releasing the file handle itself.

D. ReadFile()

This option is incorrect because ReadFile() is used to read data from a file, not to release any resources or close the file. It has no role in the process of closing or releasing file handles.

Correct Answer

A. Kernel mode allows direct hardware access, while user mode restricts it.

Explanation

In an operating system, kernel mode and user mode are two distinct execution modes that control the level of access a program has to system resources. In kernel mode, the operating system has full access to hardware resources and can execute privileged operations such as interacting with hardware devices, managing memory, and controlling processes. In contrast, user mode is a restricted environment where applications run with limited access to system resources. This separation helps ensure that user applications do not directly interfere with critical system functions, thus improving system stability and security.

Why other options are wrong

B. User mode allows direct hardware access, while kernel mode restricts it.

This is incorrect because it is kernel mode that has direct access to hardware resources, not user mode. User mode is restricted from performing privileged operations, including direct hardware access.

C. Both modes allow the same level of access to hardware.

This is incorrect. Kernel mode has full access to system hardware, while user mode has limited access to the system and cannot interact directly with hardware without going through system calls to the kernel.

D. User mode is for system processes, while kernel mode is for user applications.

This is incorrect. User mode is for user applications, not system processes. System processes and critical operating system functions run in kernel mode, where they can access hardware and perform privileged operations.

Correct Answer

 A. In SMP, all processors share the same memory and I/O resources, while non-SMP systems do not.

Explanation

SMP (Symmetric Multiprocessing) systems are designed to use multiple processors that all share the same memory and I/O resources. This means that each processor has equal access to memory and input/output devices, enabling them to work together on tasks concurrently. In contrast, non-SMP systems typically feature a single processor or multiple processors that do not share memory or I/O resources in the same way, often requiring specialized hardware for interprocessor communication. SMP systems are more efficient for parallel processing due to their shared resource structure.

Why other options are wrong

B. SMP systems have a single processor that handles all tasks, whereas non-SMP systems have multiple processors.

This is incorrect because SMP systems are defined by having multiple processors, not a single one. Non-SMP systems may have a single processor, but SMP systems rely on multiple processors that share resources.

C. In SMP, each processor has its own dedicated memory, while non-SMP systems share memory.

This is incorrect because, in SMP systems, all processors share the same memory. It is non-SMP systems that often have separate memory for each processor, leading to complex memory management and communication.

D. SMP systems can only run one process at a time, while non-SMP systems can run multiple processes simultaneously.

This is incorrect because SMP systems are designed to run multiple processes simultaneously by leveraging multiple processors. Non-SMP systems, with a single processor, can only run one process at a time unless time-sharing or multitasking techniques are employed.