Xem 1-20 trên 349 kết quả Various conceptions
  • Nanotechnology is an often misunderstood term. Say the word, and you are likely to elicit various conceptions from complete ignorance of the term to the fear of a science fiction type mass assembler that threatens the world. 2 The term has come to mean different things to different people. “Nano” is a prefix meaning one-billionth. In distance, a nanometer is one billionth of a meter. As illustration, a human hair is 100,000 nanometers (nm) in width. A red blood cell measures approximately 5,000 nm across. Ten hydrogen atoms, lined up side by side, if...

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  • Module 21 - The UNIX system. Although operating system concepts can be considered in purely theoretical terms, it is often useful to see how they are implemented in practice. This chapter presents an in-depth examination of the 4.3BSD operating system, a version of UNIX, as an example of the various concepts presented in this lecture. By examining a complete, real system, we can see how the various concepts discussed in this book relate both to one another and to practice.

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  • The Aim of "Current Concepts of General Thoracic Surgery" is to provide a brief overview of several topics in this field. It includes a collection of contributions from many outstanding Authors who provide their knowledge and experience from many countries around the world. We apologize for the chapters reviewed that have were not chosen for publication in this book; however, according to the single centres experience, the final result offers thorough and precious information on the several topics evaluated by the Authors....

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  • In this chapter you will learn: To introduce CPU scheduling, which is the basis for multiprogrammed operating systems, to describe various CPU-scheduling algorithms, to discuss evaluation criteria for selecting a CPU-scheduling algorithm for a particular system, to examine the scheduling algorithms of several operating systems.

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  • In this chapter: To provide a detailed description of various ways of organizing memory hardware, to discuss various memory-management techniques, including paging and segmentation, to provide a detailed description of the Intel Pentium, which supports both pure segmentation and segmentation with paging.

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  • This chapter includes contents: To discuss security threats and attacks; to explain the fundamentals of encryption, authentication, and hashing; to examine the uses of cryptography in computing; to describe the various countermeasures to security attacks.

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  • In this chapter, you learned to: To explore the history and benefits of virtual machines, to discuss the various virtual machine technologies, to describe the methods used to implement virtualization, to show the most common hardware features that support virtualization and explain how they are used by operatingsystem modules.

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  • This chapter discusses the various forms of return encountered in investment management. Among the return types discussed are required returns, which will be used later in the text for equity valuation. The required return is what the investor expects to earn on an investment, given the investment’s risk. To determine the required return, we will use several different models, such as the capital asset pricing model (CAPM).

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  • In this chapter, we discuss various ways to manage memory. The memory- management algorithms vary from a primitive bare-machine approach to paging and segmentation strategies. Each approach has its own advantages and disadvantages. Selection of a memory-management method for a specific system depends on many factors, especially on the hardware design of the system. As we shall see, many algorithms require hardware support, leading many systems to have closely integrated hardware and operating-system memory management.

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  • Software design encompasses the set of principles, concepts, and practices that lead to the development of a high-quality system or product. Design principles establish an overriding philosophy that guides you in the design work you must perform. Design concepts must be understood before the mechanics of design practice are applied, and design practice itself leads to the creation of various representations of the software that serve as a guide for the construction activity that follows.

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  • Chapter 11 probe below the higher levels as we describe various methods for implementing the data models and languages presented in preceding chapters. This chapter presents the following content: Overview of physical storage media, magnetic disks, raid, tertiary storage, storage access, file organization, organization of records in files, data­dictionary storage.

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  • Chapter 3 - Operating-system structures, provides new coverage of user interfaces for mobile device s, including d iscussions of iOSand A ndroid, and expanded coverage of Mac OS Xas a type of hybrid system. The objectives of this chapter are to describe the services an operating system provides to users, processes, and other systems; to discuss the various ways of structuring an operating system, to discuss the various ways of structuring an operating system.

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  • Chapter 4 - Processes, now includes coverage of multitasking in mobile operating systems, support for the multiprocess model in Google’s Chrome web browser, and zombie and orphan processes in UNIX. The objectives of this chapter are to introduce the notion of a process a program in execution, which forms the basis of all computation; to describe the various features of processes, including scheduling, creation, and termination; to explore interprocess communication using shared memory and mes- sage passing.

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  • A cooperating process is one that can affect or be affected by other processes executing in the system. Cooperating processes can either directly share a logical address space (that is, both code and data) or be allowed to share data only through files or messages. The former case is achieved through the use of threads, discussed in chapter 4. Concurrent access to shared data may result in data inconsistency, however.

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  • In this chapter, we discuss various ways to manage memory. The memory- management algorithms vary from a primitive bare-machine approach to paging and segmentation strategies. Each approach has its own advantages and disadvantages. Selection of a memory-management method for a specific system depends on many factors, especially on the hardware design of the system. As we shall see, many algorithms require hardware support, leading many systems to have closely integrated hardware and operating-system memory management.

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  • In chapter 7, we discussed various memory-management strategies used in computer systems. All these strategies have the same goal: to keep many processes in memory simultaneously to allow multiprogramming. However, they tend to require that an entire process be in memory before it can execute. Virtual memory is a technique that allows the execution of processes that are not completely in memory. In this chapter, we discuss virtual memory in the form of demand paging and examine its complexity and cost.

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  • In this chapter, we consider the various aspects of files and the major directory structures. We also discuss the semantics of sharing files among multiple processes, users, and computers. Finally, we discuss ways to handle file protection, necessary when we have multiple users and we want to control who may access files and how files may be accessed.

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  • Chapter 16 looks at the current major research and development in distributed-file systems (DFS). The purpose of a DFS is to support the same kind of sharing when the files are physically dispersed among the various sites of a distributed system.

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  • Chapter 17 examines various mechanisms for process synchronization and communication, as well as methods for dealing with the deadlock problem, in a distributed environment. In addition, since a distributed system may suffer from a variety of failures that are not encountered in a centralized system, we also discuss here the issue of failure in a distributed system.

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  • The various processes in an operating system must be protected from one another’s activities. For that purpose, various mechanisms exist that can be used to ensure that the files, memory segments, CPU, and other resources can be operated on by only those processes that have gained proper authorization from the operating system. In this chapter, we examine the problem of protection in great detail and develop a unifying model for implementing protection.

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