The multiplicity of intruding a computing system makes computer security difficult.（)

in taverns, coffee-houses, and other places of public resort, I have thereby an opportunity of observing an infinite variety of characters, which, to a person of contemplative turn, is a much higher entertainment than a view of all the curiosities of art or nature. Amongst a multiplicity of other topics, we took occasion to talk of the different characters of the several nations of Europe; when one of the gentlemen, cocking his hat, and assuming such an air of importance as if he had possessed all the merit of the English nation in his own person, declared that the Dutch were a parcel of avaricious wretches; the French a set of flattering sycophants; that the Germans were drunken sots, and beastly gluttons; and the Spaniards proud, haughty, and surly tyrants; but that in bravery, generosity, clemency, and in every other virtue, the English excelled all the rest of the world.

of exclusive information societies has restarted【M1】______ the debate about cultural diversity by renewing the common perception and evolution of this elusive term We shall focus on the meaning of the two words "diversity" and "culture". Diversity is often perceived as disparity, variation, singularity, that is, the opposite of uniformity and【M2】______ homogeneity. In its first and literal sense, cultural diversity then refers quite simply the multiplicity of cultures or cultural identities. This【M3】______ vision has now been replaced, though As for many experts "diversity" is not so much defined in opposite to "homogeneity". It is synonymous【M4】______ with dialogue and sharing values. In fact, the concept of cultural【M5】______ diversity, like that of biodiversity, goes on further, because it considers【M6】______ the multiplicity of cultures in a systemic perspective when each culture【M7】______ develops and evolves through contact with other cultures. As to culture, it draws its origins from the Latin word "cultura", that indicated the【M8】______ cultivation of fields and cattle. In the sixteenth century it acquires the meaning of the action of cultivating, or formation, which is at the【M9】______ source of the sense it is given today. So, culture has then come to mean that whole complexity of meanings, values and beliefs that determine【M10】______ how we do things and how we structure our ways of thinking.

【M1】

congressionally imposed secrecy in June 1776 for a country wracked by military and political uncertainties. In anticipation of a vote for independence, the Continental Congress on June 11 appointed Thomas Jefferson, John Adams, Benjamin Franklin, Roger Sherman, and Robert R. Livingston as a committee to draft a declaration of independence. The committee then delegated Thomas Jefferson to undertake the task. Jefferson worked diligently in private for days to compose a document. Proof of the arduous nature of the work can be seen in the fragment of the first known composition draft of the declaration, which is on public display here for the first time.

Jefferson then made a clean or "fair" copy of the composition declaration, which became the foundation of the document, labeled by Jefferson as the "original Rough draught. " Revised first by Adams, then by Franklin, and then by the full committee, a total of forty-seven alterations including the insertion of three complete paragraphs was made on the text before it was presented to Congress on June 28. After voting for independence on July 2, the Congress then continued to refine the document, making thirty-nine additional revisions to the committee draft before its final adoption on the morning of July 4. The "Original Rough Draught" embodies the multiplicity of corrections, additions and deletions that were made at each step. Although most of the alterations are in Jefferson's handwriting (Jefferson later indicated the changes he believed to have been made by Adams and Franklin), quite naturally he opposed many of the changes made to his document.

Congress then ordered the Declaration of Independence printed and late on July 4, John Dunlap, a Philadelphia printer, produced the first printed text of the Declaration of Independence, now known as the "Dunlap Broadside. " The next day John Hancock, the president of the Continental Congress, began dispatching copies of the Declaration to America's political and military leaders. On July 9, George Washington ordered that his personal copy of the "Dunlap Broadside," sent to him by John Hancock on July 6, be read to the assembled American army at New York. In 1783 at the war's end, General Washington brought his copy of the broadside home to Mount Vernon. This remarkable document, which has come down to us only partially intact, is accompanied in this exhibit by a complete "Dunlap Broadside"—one of only twenty-four known to exist.

On July 19, Congress ordered the production of an engrossed (officially inscribed) copy of the Declaration of Independence, which attending members of the Continental Congress, including some who had not voted for its adoption, began to sign on August 2, 1776. This document is on permanent display at the National Archives.

On July 4, 1995, more than two centuries after its composition, the Declaration of Independence, just as Jefferson predicted on its fiftieth anniversary in his letter to Roger C. Weightman, towers aloft as "the signal of arousing men to burst the chains.., to assume the blessings and security of self-government" and to restore "the free right to the unbounded exercise of reason and freedom of opinion. "

Drafting the Declaration of Independence. ______.

A．was an artful work

B．involved a lot of efforts

C．was an ardent work

D．was rather easy for Jefferson

Parallel Computer Models

并行模式

Parallel processing has emerged as a key enabling technology in modern computers, driven by the ever-increasing demand for higher performance, lower costs, and sustained productivity in real-life applications. Concurrent events are taking place in today's high- performance computers due to the common practice of multiprogramming, multiprocessing, or multicomputing.

Parallelism appears in various forms, such as lookahead, pipelining, vectorization, concurrency, simultaneity, data parallelism, partitioning, interleaving, overlapping, multiplicity, replication, time sharing, space sharing, multitasking, multiprogramming, multithreading, and distributed computing at different processing levels.

In this part, we model physical architectures of parallel computers, vector super- computers^[1], multiprocessors, multicomputers, and massively parallel processors. Theoretical machine models are also presented, including the parallel random-access machines (PRAMs)^[2]and the complexity model of VLSI (very large-scale integration) circuits. Architectural development tracks are identified with case studies in the article. Hardware and software subsystems are introduced to pave the way for detailed studies in the subsequent section.

The State of Computing

Modern computers are equipped with powerful hardware facilities driven by extensive software packages. To assess state-of-the-art^[3]computing, we first review historical milestones in the development of computers. Then we take a grand tour of the crucial hardware and software elements built into modern computer systems. We then examine the evolutional relations in milestone architectural development. Basic hardware and software factors are identified in analyzing the performance of computers.

Computer Development Milestones

Computers have gone through two major stages of development: mechanical and electronic. Prior to 1945, computers were made with mechanical or electromechanical parts. The earliest mechanical computer can be traced back to 500 BC in the form of the abacus used in China. The abacus is manually operated to perform decimal arithmetic with carrying propagation digit by digit.

Blaise Pascal built a mechanical adder/subtractor in France in 1642. Charles Babbage designed a difference engine in England for polynomial evaluation in 1827. Konrad Zuse built the first binary mechanical computer in Germany in 1941. Howard Aiken^[4]proposed the very first electromechanical decimal computer, which was built as the Harvard Mark I^[5]by IBM in 1944. Both Zuse's and Aiken's machines were designed for general-purpose computations.

Obviously, the fact that computing and communication were carried out with moving mechanical parts greatly limited the computing speed and reliability of mechanical computers. Modern computers were marked by the introduction of electronic components. The moving parts in mechanical computers were replaced by high-mobility electrons in electronic computers. Information transmission by mechanical gears or levers was replaced by electric signals traveling almost at the speed of light.

Computer Generations

Over the past five decades, electronic computers have gone through five generations of development. Each of the first three generations lasted about 10 years. The fourth generation covered a time span of 15 years. We have just entered the fifth generation with the use of processors and memory devices with more than 1 million transistors on a single silicon chip.

The division of generations is marked primarily by sharp changes in hardware and software technologies. Most features introduced in earlier generations have been passed to later generations. In other words, the latest generation computers have inherited all the nice features and eliminated all the bad ones found in previous generations.

Elements of Modern Computers

Hardware, software, and programming elements of a modern computer system are briefly introduced below in the context of parallel processing.

Computing Problems

It has been long recognized that the concept of computer architecture is no longer restricted to the structure of the bare machine hardware. A modern computer is an integrated system consisting of machine hardware, an instruction set, system software, application programs, and user interfaces. These system elements are depicted in Fig. 1. The use of a computer is driven by real-life problems demanding fast and accurate solutions. Depending on the nature of the problems, the solutions may require different computing resources.

For numerical problems in science and technology, the solutions demand complex mathematical formulations and tedious integer or floating-point computations. For alphanumerical problems in business and government, the solutions demand accurate transactions, large database management, and information retrieval operations.

For artificial intelligence (AI) problems, the solutions demand logic inferences and symbolic manipulations. These computing problems have been labeled numerical computing, transaction processing, and logical reasoning. Some complex problems may demand a combination of these processing modes.

Algorithms and Data Structures

Special algorithms and data structures are needed to specify the computations and communications involved in computing problems. Most numerical algorithms are deterministic, using regularly structured data. Symbolic processing may use heuristics or nondeterministic searches over large knowledge bases.

Problem formulation and the development of parallel algorithms often require interdisciplinary interactions among theoreticians, experimentalists, and computer programmers. There are many books dealing with the design and mapping of algorithms or heuristics onto parallel computers. In this article, we are more concerned about the resources mapping problems than the design and analysis of parallel algorithms.

Hardware Resources

The system architecture of a computer is represented by three nested circles on the right in Fig. 1. A modern computer system demonstrates its power through coordinated efforts by hardware resources, an operating system, and application software. Processors, memory, and peripheral devices form the hardware core of a computer system. We will study instruction-set processors, memory organization, multiprocessors, supercomputers, multicomputers, and massively parallel computers.

Special hardware interfaces are often built into I/O devices, such as terminals, workstations, optical page scanners, magnetic ink character recognizers, modems, file servers, voice data entry, printers, and plotters. These peripherals are connected to mainframe computers directly or though local or wide-area networks.

In addition, software interface programs are needed. These software interfaces include file transfer systems, editors, word processors, device drivers, interrupt handlers, network communication programs, etc. These programs greatly facilitate the portability of user programs on different machine architectures.

Operating System

An effective operating system manages the allocation and deal-location of resources during the execution of user programs. We will study UNIXE^[6]extensions for muhiprocessors and muhicomputers later. Mach/OS kernel and OSF/1^[7]will be specially studied for muhithreaded kernel functions, virtual memory management, file subsystem, and network communication services. Beyond the OS, application software must be developed to benefit the users. Standard benchmark programs are needed for performance evaluation.

Notes

[1] vector super-computers: 向量巨型机体系机构。向量巨型计算机的体系机构，目前大多数仍为多流水线结构，也有的采用并行处理机构。

[2] parallel random-access machines(PRAMs)：并行随机存取机器具有任意多个处理器，以及分别用于输入、输出和工作的存储器的机器模型。

[3] state-of-the-art：最新技术水平；当前正在发展的技术，或者在当前应用中保持领先地位的技术。

[4] Howard Aiken: Mark I计算机的设计者。

[5] Harvard Mark I：哈佛Mark I计算机。Mark I计算机是一种在30年代末40年代初由(美国)哈佛大学的Howard Aiken设计并由IBM公司制造的机电式计算器。

[6] UNIX：UNIX操作系统。

[7] Mach/OS kernel and OSF/1：Mach操作系统/OS操作系统，Kernel核心程序。在操作系统中，实现诸如分配硬件资源、进程调度等基本功能的程序，是与硬件机器直接打交道的部分，始终驻留内存。OSF/1开放软件基金会/1。

Choose the best answer for each of the following: