What is a system call?

Question

BlackTom AI · Accepted Answer

When approaching the concept of a system call, we evaluate what each option claims about how user programs interact with the operating system.
Option 1 suggests: 'A function written by the user that directly manipulates kernel memory for faster execution.' This is inaccurate because user programs do not directly manipulate kernel memory; doing so would break protection and is not how system calls operate. Access to kernel memory is restricted for safety and stability, and system calls provide a controlled interface instead.
Option 2 claims: 'A hardware instruction that allows applications to bypass the operating system and access devices directly.' In reality, there is no standard mechanism for applications to bypass the OS; devices are accessed through system calls and device drivers managed by the kernel. This option describes unauthorized privileged access, which system calls are designed to prevent.
Option 3 states: 'A request to the operating system kernel to perform privileged operations that user programs cannot do directly.' This matches the canonical definition of a system call: a controlled entry into the kernel from user space to perform operations that require higher privileges, such as file I/O, process management, or inter-process communication.
Option 4 asserts: 'A library function that executes in user mode but pretends to be the kernel.' While libraries can wrap system calls or provide abstractions, they do not execute in kernel space and cannot impersonate the kernel. Real kernel actions happen through actual system calls into the kernel, not through user-space libraries pretending to be kernel code.
In summary, Option 3 provides the precise mechanism by which user-space programs request privileged operations from the kernel, aligning with the standard OS design: user mode to kernel mode transitions via system calls. The other options describe incorrect or misleading mechanisms that would violate protection boundaries and OS architecture.

INFO1112 (ND) Weekly-quiz-04-2025

What is a system call?

查看解析

登录即可查看完整答案

类似问题

Question at position 8 A System call is a: Library function that uses user/ kernel stubs to carry out the service task by running its code in the kernel modePrivileged instruction that run in the kernel modeKernel function that my be called only within the kernelClear my selection

Which of the following orderings is from fastest to slowest?

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

Which of the following statement regarding cost is correct:

Under the assumptions used in cost-volume-profit analysis, as the activity increases:

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单