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OS Exam 1

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Section 1

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What are the three main purposes of an operating system?

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Mar 1, 2020

Cards (7)

Section 1

(7 cards)

What are the three main purposes of an operating system?

Front

Answer: To provide an environment for users to execute programs on the computer. To allocate the computer resources needed to execute the program safely. To provide a foundation to future services

Back

Distinguish between the client-server and peer-to-peer models of distributed systems

Front

Client-Server Model: A server manages most processes and stores all data. A client requests specified data or processes. The server relays process output to the client. Peer-to-Peer: A network where individuals can share resources directly without a central server

Back

What is the purpose of interrupts? How does an interrupt differ from a trap? Can traps be generated intentionally by a user program? If so, for what purpose?

Front

Answer: An interrupt is a hardware‐generated change‐of‐flow within the system to deal with the cause of the interrupt; control is then returned to the interrupted context and instruction. A trap is a software‐generated interrupt. An interrupt can be used to signal the completion of an I/O to obviate the need for device polling. A trap can be used to call operating system routines or to catch arithmetic errors.

Back

What are the advantages and disadvantages of using the same system-call interface for manipulating both files and devices?

Front

Advantage: Each device can be accessed as though it was a file in the file system, and it is relatively easy to add a new device driver by implementing the hardware-specific code to support this abstract file interface. Disadvantage: The disadvantage with using the same interface is that it might be difficult to capture the functionality of certain devices within the context of the file access API.

Back

What system calls have to be executed by a command interpreter or shell in order to start a new process on a UNIX system?

Front

In Unix systems, a fork() system call followed by an exec() system call need to be performed to start a new process.

Back

What is the main advantage of the microkernel approach to system design? How do user programs and system services interact in a microkernel architecture? What are the disadvantages of using the microkernel approach?

Front

Advantages: (1) adding a new service does not require modifying the kernel, (2) it is more secure as more operations are done in user mode than in kernel mode,and (3) a simpler kernel design and functionality typically results in a more reliable operating system. User programs and system services interact in a microkernel architecture by using interprocess communication mechanisms such as messaging. These messages are conveyed by the operating system Disadvantages of the microkernel architecture are the frequent use of the operating system's messaging functions in order to enable the user process and the system service to interact with each other.

Back

What is the main advantage of the layered approach to system design? What are the disadvantages of the layered approach?

Front

Advantage: It allows good maintenance, where you can make changes without affecting layer interfaces Disadvantage: It is difficult to exactly assign of functionalities to the correct and appropriate layer

Back