Os Assignment

Topics: Operating system, Computer multitasking, Computer program Pages: 6 (1231 words) Published: September 29, 2010

Q1. In a multiprogramming and time-sharing environment, several users share the system simultaneously. This situation can result in various security problems.
a. What are two such problems?
b. Can we ensure the same degree of security in a time-shared machine as in a dedicated machine? Explain your answer?

Stealing or copying a user's files; writing over another program's (belonging to another user or to the OS) area in memory; using system resources (CPU, disk space) without proper accounting; causing the printer to mix output by sending data while some other user's file is printing.

Probably we cannot assure the same degree of security in a time shared machine as in a dedicated machine, since any protection scheme devised by a human can also be broken -- and the more complex the scheme is, the more difficult it is to be confident of its correct implementation.

Q2. Which of the functionalities listed below need to be supported by the operating system for the following two settings: (a) handheld devices and (b) real-time systems? a. Batch programming

b. Virtual memory
c. Time sharing

For hand held systems, the operating system needs to provide virtual memory, but does not need to provide time-sharing.

For real-time systems, the operating system needs to support virtual memory and time sharing in a fair manner.

Batch programming is not necessary in both settings.

Q3. Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?

Symmetric processing treats all processors as equals; I/O can be processed on any of them. 

Asymmetric processing designates one CPU as the master, which is the only one capable of performing I/O; the master distributes computational work among the other CPUs.

|Advantages |Disadvantage | |Multiprocessor systems can save money, by sharing power supplies, |Multiprocessor systems are more complex in both hardware and | |housings, and peipherals. |software. | |Can execute programs more quickly. |Additional CPU cycles are required to manage the cooperation, so | | |per-CPU efficiency goes down. | |Can have increased reliability. | |

Q4. How do clustered systems differ from multiprocessor systems? What is required for two machines belonging to a cluster to cooperate to provide a highly available service?


|Clustered Systems |Multiprocessor Systems | |Clustered systems are typically constructed by combining multiple |Multiprocessor systems on the other hand could be a single | |computers into a single system to perform a computational task |physical entity comprising of multiple CPUs. | |distributed across the cluster. | | |It is less tightly coupled. |It is tightly coupled. | |Clustered systems communicate using messages. |While processors in a multiprocessor system could communicate | | |using shared memory | | |...
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