《专业英语》课程作业

步京侄宛a琴《专业英语》课程作业学生姓名____________________________学号 __________________________院系 _________________________专业 __________________________任课教师____________________________二0一五年六月一、英译中(英文科技资料翻译)原文：An operating system is the software which acts as an interface between a user of a computer and the computer hardware.The purpose of an operating system is to provide an environment in which a user may execute program. The primary goal of an operating system is thus to make the computer system convenient to use. A secondary goal is to use the computer hardware in an efficient way.We can view an operating system as a resource allocator. A computer system has many resources which may be required to solve a problem: CPU time, memory space, , input/output(I/O) devices, and so on.The operating system acts as the manager of these resources and allocates them to specific programs and users as necessary for their tasks. Since there may be many, possibly conflicting, requests for resources, the o/s must decide which requests are allocated resources to operate the computer system fairly and efficiently. Multimedia means, from the user ' perspective, that computer information can be represented through audio and/or video, in addition to text, image, graphics and animation .The integration of these media into the computer provides additional possibilities for the use of computational power currently available (e.g., for interactive presentation of huge amounts of information ). Furthermore, these data can be transmitted though computer and telecommunication networks, which implies applications in the areas of information distribution and cooperative work.Multimedia provides the possibility for a spectrum of new applications, many of which are in place today.A multimedia system distinguishes itself from other systems through several properties. We elaborate on the most important properties such as combination of the media, media-independence, computer control and integration.Not every arbitrary combination of media justifies the usage of the term multimedia.A simple text processing program with incorporated images is often called a multimedia application because two media are processed through one program.But one should talk about multimedia only when both continuous and discrete media are utilized.A text processing program with incorporated images is therefore not a multimedia application.An important aspect of different media is their level of independence from each other. In general, there is a request for independence of different media, but multimedia may require several levels of independence. On the one hand, a computer-controlled video recorder stores audio and video information, but there is an inherently tight connection between the two types of media. Both media are coupled together through the common storage medium of the tape. On the other hand, for the purpose of presentations, the combination of DAT recorder (Digital Audio Tape) signals and computer-available text satisfies the request for media-independence.Early computers were(physically) very large machines run from a console.The programmer wouldwrite a program and then operate the program directly from the operator Software sdchs console. as assemblers, loaders, and compilers improved on the convenience of programming the system, but also required substantial set-up time. To reduce the setup time, operators were hired and similar jobs were batched together.Batch systems allowed automatic job sequencing by a resident monitor and improved the overall utilization of the computer greatly.The computer no longer had to wait for human operation. CPU utilization was still low, however, because of the slow speed of the I/O devices relative to the CPU. Offline operation of slow devices was tried.Buffering was another approach to improving system performance by overlapping the input, output, and computation of a single job. Finally, spooling allowed the CPU to overlap the input of one job with the computation and output of other jobs.Spooling also provides a pool of jobs which have been read and are waiting to be run. This job pool supports the concept of multiprogramming. With multiprogramming, several jobs are kept in memory at one time; the CPU is switched back and forth between them in order to increase CPU utilization and to decrease the total real time needed to execute a job.Multiprogramming, which was developed to improve performance, also allows time sharing.Time-shared operating systems allow many users (from one to several hundred) to use a computer system interactive at the same time. As the system switches rapidly from one user to the next, each user is given the impression that he has his own computer. Other operating systems types include real-time systems and multiprocessor systems.A real-time system is often used as control device in a dedicated application. Sensors bring data to the computer. The computer must analyze the data and possibly adjust controls to modify the sensor inputs. Systems, which control scientific experiments, medical computer systems, industrial control systems, and some display systems are real-time systems. A real-time operating system has well-defined fixed time constraints . Processing must be done within the defined constraints, or the system will fail.A multiprocessor system has more than one CPU. The obvious advantages would appear to be greater computing power and reliability. There are various types of operating systems for multiprocessors and multicomputers. It is more or less possible to distinguish two kinds of operating systems for multiple CPU systems: Loosely coupled, such as network operating system and distributed o/s, and tightly coupled, such as parallel o/s. As we shall see, loosely and tightly-coupled s/w is rought analogous to loosely and tight-coupledh/w.The operating system must ensure correct operation of the computer system. To prevent user programs from interfering with the proper operation of the system, the h/w was modified to create two modes: user mode and monitor mode. Various instructions(such as I/O instructions and halt instructions) are privileged and can only be executed in monitor mode. The memory in which the monitor resides must also be protected from modification by the user. A time prevents infinite loops. Once these changes (dual mode, privilegedinstructions, memory protection, timer interrupt) have been made to the basic computer architecture, it is possible to write a correct operating system.译文：操作系统是作为计算机用户和计算机硬件之间接口的软件。