Operating System (Assignment)

1. In a multiprogramming and time sharing environment, several users share the system simultaneously. This situation can results in various security problems. a. What are the two such problems? Ans: The two problems in Multiprogramming and time sharing environment are 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. ttp://wiki. answers. com/Q/What_are_the_main_two_problems_in_multiprogramming_environment_when_processes_are_run_concurrently_and_share_the_resources b. Can we ensure the same degree of security in a time shared machine as in a dedicated machine? Explain. Ans: No, because time-shared machines are far less secure, and are very easy to overload the buffers. Also they are much slower to catch a virus. http://wiki. answers. com/Q/Can_we_ensure_the_same_security_in_a_time-shared_machine_as_in_a_dedicated_machine . The issue of resource utilization shows up in differenct forms in different types of operating systems. List what resources must be manged carefully in the following settings: a. Mainframe or Minicomputer systems Ans: Memory, CPU, Storage b. Workstations connected to servers Ans: Storage, Network Bandwidth c. Handheld computers Ans: Memory, CPU, Storage, Power 3. Describe the difference symmetric and asymmetric multiprocessing. What are three advantages and one disadvantages of multiprocessor system? Ans:

The difference between symmetric and asymmetric multiprocessing is that in Symmetric processing treats all processors as equals; I/O can be processed on any of them, while 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. Advantagesmultiprocessor system: ?Can save money, by sharing power supplies, housings, and peripherals ? Can execute programs more quickly ?Can have increased reliability Disadvantagesmultiprocessor system: More complex in both hardware and software. Additional CPU cycles are required to manage the cooperation, so per-CPU efficiency goes down. http://www. studymode. com/essays/Os-Assignment-419243. html 4. Distinguish between the client server and peer to peer models of distributed systems. Ans: A client-server model can be defined as a centralized environment, where all users, objects, resources, and so on are administered in a centralized location and can, if configured, use any network resources on any workstation on the domain. while a Peer-to-peer model can be defined as a decentralized environment, where the user must be assigned permissions on each workstation in order to access any available resources. 5. What is the purpose of interrupts? What are the difference between a trap and an interrupt? Can traps be generated intentionally by a user program? If so, for what purpose? Ans: The difference between Interrupt and Trap is that Interrupt is a hardware-generated signal that changes the flow within the system. While a trap is a software-generated interrupt. 6.

Define the essential properties of the following types of operating systems. a. Batch: Jobs with similar needs are batched together and run through the computer as a group, by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multiprogramming. b. Interactive: Composed of many short transactions with input and output read/written on the screen; the results and timing of the next transaction may be unpredictable. Note that a urely interactive system (no time-sharing) only has one user; e. g. , a PC). c. Time-sharing: Uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The CPU switches rapidly from one user to another. d. Real-time: The system must respond to inputs/commands within a fixed amount of time to ensure correct performance. Input is typically read from sensors. e. Network:Consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic communications.

The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. f. Parallel:More than one event happening at a time. It is usually contrasted with serial, meaning only one event happening at a time. g. Distributed: Divides computation up among several computers. The computers do not share memory or a clock; they communicate with each other over communication lines (e. g. , high-speed bus, telephone line). h. Clustered: i. Handheld:A handheld computer is a computer that can conveniently be stored in a pocket (of sufficient size) and used while you’re holding it.

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