計算機技術簡介外文翻譯

1、<p><b>　　外文資料</b></p><p>　　Parts of computer technique brief introduction</p><p>　　Compendium</p><p>　　Computer technique more the renewal being placed in continuou

2、sly changes the on behalf inside, each a strenuous efforts for new technical emergence all coagulating numerous person.In this article, we simple introduction some of that.</p><p>　　Search Engines</p>

3、<p>　　Internet search tools fall into two camps：search engines, such as HotBot and AltaVista，and online directories，such as Yahoo and Lycos．The difference between the two is related to how they compile their site

4、 listings．Of course，there are exceptions to every rule．Some search utilities such as Ask Jeeves，combine the search engine and directory approaches into a single package，hoping to provide users with the best of both world

5、s． </p><p>　　In directory-based search services，the Web site listings are compiled manually．For example，the everpopular Yahoo dedicates staff resources to accept site suggestions from users review and catego

6、rize them，and add them to a specific directory on the Yahoo site．</p><p>　　You can usually submit your Web site simply by filling out an online form．On Yahoo,for example,you'll find submission informatio

7、n at www.yahoo.com/docs/info/include.html．Because human intervention is necessary to process，verify，and review submission requests，expect a delay before your site secures a spot in a directory-based search service． </

8、p><p>　　On the flip side，search engines completely automate the compilation process，removing the human component entirely． </p><p>　　A software robot，called a spider or crawler，automatically fetche

9、s sites all over the Web，reading pages and following associated links．By design，a spider will return to a site periodically to check for new pages and changes to existing pages． </p><p>　　Results from spider

10、ing are recorded in the search engine’s index or catalog．Given the wealth of information available on the Internet，it is not surprising that indexes grow to very large sizes．For example，the AltaVista index has recently b

11、een increased to top out at 350 million pages．This may seem like a mammoth number，but by all estimates it still represents less than 35 percent of all pages on the Web． </p><p>　　Because of the depth and bre

12、adth of information being indexed，there is usually a delay，sometimes up to several weeks，between the time a site has been“spidered”and when it appears in a search index．Until this two-step process has been completed，a si

13、te remains unavailable to search queries． </p><p>　　Finally，the heart of each search engine is an algorithm that matches keyword queries against the information in the index，ranking results in the order the

14、algorithm deems most relevant． </p><p>　　Because the spiders，resulting indexes，and search algorithms of each search engine differ，so do the search results and rankings across the various search engines．This

15、explains why a top 10 site in HotBot may not appear near the top of Alta Vista when the same keyword search criterion is entered． </p><p>　　In addition，many，but not all，search utilities also reference metata

16、gs—invisible HTML tags within documents that describe their content—as a way to control how content is indexed．As a result，proper use of metatags throughout a site can also boost search engine ranking</p><p>

17、;　　Advanced Encryption Standard</p><p>　　For the past three years，the National Institute of Standards and Technology (NIST) has been working to develop a new encryption standard to keep government informatio

18、n secure．The organization is in the final stages of an open process of selecting one or more algorithms，or data-scrambling formulas，for the new Advanced Encryption Standard (AES) and plans to make adecision by late summe

19、r or early fall．The standard is slated to go into effect next year．</p><p>　　AES is intended to be a stronger，more efficient successor to Triple Data Encryption Standard (3DES)，which replaced the aging DES，w

20、hich was cracked in less than three days in July 1998． </p><p>　　“Until we have the AES，3DES will still offer protection for years to come．So there is no need to immediately switch over，”says Edward Roback，a

21、cting chief of the computer security division at NIST and chairman of the AES selection committee．“What AES will offer is a more efficient algorithm．It will be a federal standard，but it will be widely implemented in the

22、IT community．” </p><p>　　According to Roback，efficiency of the proposed algorithms is measured by how fast they can encrypt and decrypt information，how fast they can present an encryption key and how much in

23、formation they can encrypt． </p><p>　　The AES review committee is also looking at how much space the algorithm takes up on a chip and how much memory it requires．Roback says the selection of a more efficient

24、 AES will also result in cost savings and better use of resources． </p><p>　　“DES was designed for hardware implementations，and we are now living in a world of much more efficient software，and we have learne

25、d an awful lot about the design of algorithms，”says Roback．“When you start multiplying this with the billions of implementations done daily，the saving on overhead on the networks will be enormous．” </p><p>　

26、　The process of selecting the algorithm for AES has been notable for its openness and transparency．This is a marked departure from the government's past inclination toward secrecy in discussing encryption standards，w

27、hich led to the public cracking of DES after critics questioned the government's assertion that the standard was still secure． </p><p>　　NIST kicked off the selection process in September 1997．Conference

28、s were held in August 1998 and March 1999；cryptographers from around the world discussed the algorithm candidates and helped narrow the list to 15 and then to five finalists：IBM's MARS；RSA Laboratories* RC6 ；Joan Dae

29、men and Vincent Rijmen's Rijndael；Ross Andersen，Eli Baham and Lars Knudsen's Serpent；and Counterpane Labs* Twofish．</p><p>　　While most evaluators of the algorithms want to avoid complexity by select

30、ing one to serve as a standard，there's a minority that wants to select more than one．</p><p>　　Digital Wallets</p><p>　　A digital wallet is software that enables users to pay for goods on t

31、he Web. It holds credit-card numbers and other personal information such as a shipping address ．Once entered，the data automatically populates order fields at merchant sites.</p><p>　　When using a digital wal

32、let，consumers don't need to fill out order forms on each site when they purchase an item because the information has already been stored and is automatically updated and entered into the order fields across merchant

33、sites. Consumers also benefit when using digital wallets because their information is encrypted or protected by a private software code. And merchants benefit by receiving protection against fraud． </p><p>　

34、　Digital wallets are available to consumers free of charge，and they're fairly easy to obtain ．For example，when a consumer makes a purchase at a merchant site that's set up to handle server-side digital wallets，he

35、 types his name and payment and shipping information into the merchant's own form ．At the end of the purchase，one consumer is asked to sign up for a wallet of his choice by entering a user name and password for futur

36、e purchases ．Users can also acquire wallets at a wallet vendor's site.</p><p>　　Although a wallet is free for consumers，vendors charge merchants for wallets ． </p><p>　　Digital wallets come

37、in two main types :client-side and server- side ．Within those divisions are wallets that work only on specific merchant sites and those that are merchant agnostic ．</p><p>　　Client-based digital wallets，the

38、older of the two types，are falling by the wayside，according to analysts，because they require users to download and install software ．A user downloads the wallet application and inputs payment and mailing information ．At

39、that point，the information is secured and encrypted on the user's hard drive ．The user retains control of his credit card and personal information locally ．</p><p>　　With a server-based wallet，a user fil

40、ls out his personal information，and a cookie is automatically downloaded ．（A cookie is a text file that contains information about the user ．）In this scenario，the consumer information resides on the server of a financial

41、 institution or a digital wallet vendor rather than on the user's PC ． </p><p>　　Server-side wallets provide assurance against merchant fraud because they use certificates to verify the identity of all p

42、arties ．When a party makes a transaction，it presents its certificate to the other parties involved ．A certificate is an attachment to an electronic message used to verify the identity of the party and to provide the rece

43、iver with the means to encode a reply ．</p><p>　　Furthermore，the cardholder's sensitive data is typically housed at a financial institution，so there's an extra sense of security because financial env

44、ironments generally provide the highest degree of security ．</p><p>　　But even though wallets provide easy shopping online， adoption hasn't been widespread ． </p><p>　　Standards are pivotal

45、to the success of digital wallets.</p><p>　　New wireless LANs standard</p><p>　　With portable computers and wireless LANs,users can enjoy greater productivity while away from their desks ,whethe

46、r they are in conference rooms, public areas or remote offices.<BR>Until recently , however,wireless LANs were too slow for most enterprise applications.based on the IEEE 802.11 standdrd,they ran at 1M to 2M bit/se

47、c.</p><p>　　Now a new high -rate extension to the standard ,802.11b, lets wireless networks support data rates to 11M bit/sec.</p><p>　　Ratified in 1997 ,the original 802.11 standardunited the w

48、ireless industury by defining a low-level protocol architecture that worked with conventional upper-layer enterprise protocol stacks . also, 802.11 maintained compatibility with the three most popular radio transmission

49、types: direct sequence spread spectrum,frequency-hopping spread spectrum,and infrared.</p><p>　　Essentially,this new architecture added intelligence at the medium access control(MAC) layer 2 and at the physi

50、cal (PHY) layer 1, fosteing cooperation between the two layers in performing the critical tasks involved with initiating and maintaining wireless communi-cations.</p><p>　　For instance ,to ensure reliability

51、 of the wireless link ,MAC and PHY work togetherto determine if a clear path exists before they start a transmission.</p><p>　　During transmission, they employ special collision -avoidance and arrival-acknow

52、ledgment techniques that are not required in wired ethernet LANs.</p><p>　　in september 1999,the IEEE approved a new designation, known as 802.11.intended to retain the error-correction,security,powermanagem

53、ent and other advantages of the original , a key ingredient-a thchnique for increasing bandwidth to 11M bit/sec.</p><p>　　Called complementary code keying (CCK) the technique works only in conjunction with t

54、he DSSS technology sprcified in the original standard . it does net work with frequency-hopping or infrared transmissions.</p><p>　　What CCK does is apply sophisticated mathematical formulas to the DSSS code

55、s, a permitting the code to represent a greater volume of informitter is now able to send multiple bits of information with each DSSS code ,enough to make possible the 11M bit /sec in the original standard .</p>&

56、lt;p>　　The 802.11b standard benefits users by delivering wireless ethernet speeds of 11M bit/sec that can reliably support everyday business applications,e-mail,internet and server network access.</p><p>

57、　　With support from the new wireless ethernet from the new wireless ethernet compatibility alliance ,founded by 3com,lucent,nokia and several other companies in the wireless LAN business,the new standard will also promis

58、e certified interoperability across multivendor platforms.</p><p>　　Finally, the 802.11b standard serves as a clamoring for a simplified wireless LAN landscpape.</p><p>　　Vendors can now focus o

59、n a single ,high-speed standard , and users can cut through the clutter of wireless options by fovusing on a standard that delivers multibvendor interoperability and the performance to meet their application needs.</p

60、><p>　　Data Communication Systems</p><p>　　There are five basic types of data communication system:</p><p>　　Off-line data transmission is simply the use of a telephone or similar link

61、 to transmit data without involving a computer system .The equipment used at both ends of such a link is not part of a computer, or at least does not immediately make the data available for computer process, that is, the

62、 data when sent and/or received are 'off-line'. This type of data communication is relatively cheap and simple.</p><p>　　Remote batch is the term used for the way in which data communication technolo

63、gy is used geographically to separate the input and /or output of data from the computer on which they are processed in batch mode.</p><p>　　On-line data collection is the method of using communications tech

64、nology to provide input data to a computer as such input arises-the data are then stored in the computer (say on a magnetic disk) and processed either at predetermined intervals or as required.</p><p>　　Enqu

65、iry-response systems provide ,as the term suggests ,the facility for a user to extract information from a computer .The enquiry facility is passive ,that is ,does not modify the information stored .The interrogation may

66、be simple ,for example ,'RETRIEVE THE RECORD FOR EMPLOYEE NUMBER 1234' or complex .Such systems may use terminals producing hard copy and /or visual displays.</p><p>　　Real-time systems are those in

67、which information is made available to and processed by a computer system in a dynamic manner so that either the computer may cause action to be taken to influence events as they occur (for example as in a process contro

68、l application) or human operators may be influenced by the accurate and up-to-date information stored in the computer, for example as in reservation systems.</p><p>　　How TCP/IP Works</p><p>　　O

69、ver the past few years ,one of the most written－about network topics has been IP. But even with all this attention, few, if any ,stories have traced the protocol\'s basic workings, that is ,how routers and Layer 3 sw

70、itches act upon IP information to move Ethernet packets across the network..</p><p>　　As a point of referenced, bear in mind that IP is a member of the TCP/IP protocol suite.</p><p>　　TCP functi

71、ons at the Open Systems Interconnection(OSI)transport layer, or Layer 4.Its chief responsibility is to ensure reliable end－to－end connectivity. IP, located one layer down, at the OSI network layer, or Layer 3, communicat

72、es the addresses of each packet\'s sender and receiver to the routers along the way. Routers and Layer 3 switches can read IP and other Layer 3 protocols .This information ,combined with routing tables and other netw

73、ork intelligence ,is all it takes to get across the ro</p><p>　　The routing process begins with an IP address that is unique to the sending end station .End stations may be assigned permanent IP addresses or

74、 they may borrow them as needed from a Dynamic Host Configuration Protocol (DHCP) server or other service.</p><p>　　Each packet carries a source address, which under current (IPv4) specifications is 32 bits

75、long .In its header, each packet also carries the IP address of the final destination.</p><p>　　If the sending end station determines that the destination address is not local ,the packet goes to a first－h(huán)op

76、 router ,typically one that is close and has been preassigned to the sender.</p><p>　　The router inspects the packet\'s IP address and performs a route table lookup to see if the destination end station

77、resides on the local (physically connected) network, typically called an IP subnet .An IP subnet usually is assigned to each of the router\'s network interfaces.</p><p>　　If the destination IP address is

78、 local ,the router searches an internal store of IP addresses and local－device Media Access Control(MAC) addresses. This store is known as the Address Resolution Protocol (ARP) cache. ARP is the universal tool for matchi

79、ng IP addresses to MAC addresses. If the destination\'s MAC address appears, the router installs that MAC address in the packet header (removing its own MAC address because that\'s no longer needed) and sends the

80、 packet to the destination end stati</p><p>　　In the event that the destination MAC address does not appear in the ARP cache ―it might have timed out ,for instance― the router must broadcast an ARP request t

81、o the subnet referenced by the packet\'s destination IP address .The end station with that IP address responds, sending back its MAC address .The router updates its cache, installs the new MAC address into the packet

82、 header and launches the packet. If the route table lookup shows that the packet is destined for a non-local subnet, the ro</p><p><b>　　中文翻譯</b></p><p><b>　　部分計算機技術簡介</b>

83、</p><p><b>　　摘要</b></p><p>　　計算機技術更處于不斷的更新?lián)Q代中，每一種新技術的出現(xiàn)都凝聚了無數人的心血。在這篇文章中，我們簡單介紹一些。</p><p><b>　　搜索引擎</b></p><p>　　因特網搜索工具分為兩大陣營：搜索引擎，如HotBot和Alta

84、Vista，以及在線目錄，如Yahoo和Lycos。兩者間的差別與它們如何編撰網站編目有關。當然，對任何規(guī)律都有例外。有些搜索實用程序，如Ask Jeeves，把搜索引擎和目錄方法合并成單一的軟件包，希望把這兩個陣營中最好的東西提供給用戶。 </p><p>　　在基于目錄的搜索服務中，Web網站編目是手工編撰的。比如一直流行的Yahoo就指定專門的人力資源來接受用戶對網站的建議，并對建議進行評價和分類，再把它們

85、加到Yahoo網站上特定目錄中。</p><p>　　通常是通過簡單地填寫在線表格就能把你的網站信息提交給(搜索引擎)。例如，在Yahoo網站上，你可以在www．yahoo．com/docs/info/include．htm1上找到提交信息。由于人工干預對處理、驗證和評價提交請求是必要的，所以在網站在基于目錄的搜索服務中捕捉到一處之前，可望有些延遲。 </p><p>　　另一方面，搜索引

86、擎完全實現(xiàn)了編撰過程的自動化，徹底消除了人工干預。 </p><p>　　一個叫做蜘蛛或爬蟲的軟件機器人自動地在整個Web上取出站點，閱讀頁面和跟隨相關的鏈接。通過設計，蜘蛛可以周期性地返回到站點，檢查新的頁面和修改已有頁面。 </p><p>　　蜘蛛爬行得到的結果記錄在搜索引擎的索引或目錄中。已知了因特網上可資利用的信息的價值，對索引擴張到非常大的規(guī)模是不會感到驚訝的。例如，AltaV

87、ista的索引最近已增至3．5億頁而名列前茅。這個數字看來好像非常大，但總體估計它僅代表了Web上不足35%的頁面。 </p><p>　　由于已編索引的信息的深度與廣度(非常大)，所以通常在“蜘蛛爬行過”站點的時間與出現(xiàn)在搜索索引中的時間之間有一個延遲，有時多達幾周。只有這兩步的過程完成之后，站點才能供搜索查詢使用。 </p><p>　　最后，每個搜索引擎的心臟是一種算法，它將關鍵字查

88、詢與索引中的信息匹配起來，并按算法認為最有關聯(lián)的順序把結果列出。</p><p>　　由于每種搜索引擎的蜘蛛、產生的索引和搜索算法都是不一樣的，所以在不同搜索引擎上的搜索結果和排列次序是不同的。這就解釋了為什么當相同的關鍵字搜索準則輸入進去時，HotBot中排在最前面的10個站點不會出現(xiàn)在 AltaVista中最前面的站點中。</p><p>　　此外，很多(但不是所有的)搜索實用程序也引

89、用元標記(文檔中用來描述其內容的、看不見的HTML標記)，作為控制內容如何編索引的方法。因此，在整個站點中正確使用元標記也能提高(此站點)在搜索引擎中的排列名次。</p><p><b>　　先進加密標準</b></p><p>　　在過去三年中，（美國）國家標準與技術局（NIST）已在研究開發(fā)一種新的加密標準，以確保政府的信息安全。該組織目前正處于為新的先進加密標準

90、（AES）選擇一個或幾個算法或數據打亂公式的開放過程的最后階段，并計劃在夏末或秋初作出決定。此標準內定明年實施。</p><p>　　AES預定為比三層數據加密標準(3DES)更強、更高效的后續(xù)標準，3DES替代了老化的DES加密標準，DES在1998年7月在不到三天的時間內就被破譯了。</p><p>　　NIST計算機安全部的代理主管兼AES選擇委員會主席Edward Roback說：

91、“在我們擁有AES之前，3DES還將在今后幾年提供保護。所以沒有必要馬上轉換。AES所提供的是一種更有效的算法。它將是一項聯(lián)邦標準，但它將在IT界廣泛實施?！?</p><p>　　據Roback稱，提議中的算法的效率是通過對信息加密和解密有多快、給出加密密鑰有多快以及能對多少信息加密等幾個方面進行測量的。 </p><p>　　AES評價委員會也要看算法占據芯片上多少空間和需要多少內存。

92、Roback說，選擇一個更高效的AES也會帶來成本的節(jié)省和資源的更好利用。 </p><p>　　Roback說：“DES是為硬件實現(xiàn)而設計的，而我們現(xiàn)在處于軟件更高效的世界，我們對算法的設計有極多的了解。當我們開始大規(guī)模使用此算法，每天實現(xiàn)幾十億次的加密時，（算法帶來的）網絡開銷的節(jié)省將是巨大的?！?</p><p>　　為AES選擇算法的過程是以其公開性和透明度稱著。這標志著政府從以往

93、討論加密標準時傾向于保密的做法一刀兩斷，它導致了政府在斷言DES 標準仍是安全時被公開破譯。</p><p>　　NIST在1997年9月開始這個選擇過程。1998年8月和 1999年3月召開了會議，來自全世界的密碼專家討論了候選的算法，幫助把算法縮小到15 個，最后到了5個：IBM的MARS算法，RSA實驗室的RC6算法、Joan Daemen和Vincent Rijmen兩人的Rijndael算法、Eli B

94、aham和Lars Knudsen兩人的Serpent算法以及Counterpane 實驗室的Twofish算法。 </p><p>　　大多數算法鑒定者都選擇一個作標準以避免復雜性，但也有一小部分人要選擇多個算法。</p><p><b>　　數字錢包</b></p><p>　　數字錢包是一種能使用戶在Web網上支付貨款的軟件。它保存信用

95、卡號碼和其它個人信息，如送貨地址。數據一旦被輸入，就自動轉移到商家網站的訂貨域。</p><p>　　使用數字錢包時，當消費者購買物品時，不需要填寫每個站點上的訂單，因為信息已經存儲了，并自動更新和進入到廠商站點的訂貨域。消費者使用數字錢包時也能得到好處，因為他們的信息被加密了，即由私人軟件代碼加以保護。商家也避免了受騙而得到保護，也從中獲益。</p><p>　　對消費者來說，數字錢包是

96、免費的，可以相當容易得到。例如，當消費者在建立了處理服務器端數字錢包的商家網站上購買東西時，他把其名字、付款額和送貨信息輸入到商家自己的表格中。在購買結束時，他被要求為他選擇的錢包簽上用戶名和今后購買時的口令。用戶也能從錢包供應商的站點上得到錢包。</p><p>　　雖然錢包對消費者是免費的，但(錢包)供應商對商家使用錢包要收費。 </p><p>　　數字錢包分兩大類型：客戶端和服務器

97、端（數字錢包）。在這些分類中是那些只在某些商家網站上工作的錢包和那些商家不可知的錢包。</p><p>　　基于客戶的數字錢包是兩種錢包中較陳舊的一種，據分析人士稱，這類錢包已開始沒人理睬了，因為它們要求用戶下載和安裝軟件。用戶下載錢包的應用程序和輸入付款額和郵寄信息。在這個意義上，信息是安全的，并在用戶的硬盤上進行了加密。用戶在本地獲得對其信用卡和個人信息的控制。</p><p>　　使

98、用基于服務器的錢包時，用戶填寫其個人信息，并自動下載點心文件（點心文件是一個包括了有關用戶信息的文本文件）。在這種情況下，消費者的信息駐留在金融機構或者數字錢包供應商的服務器上，而不是用戶的PC機上。</p><p>　　服務器端錢包提供了針對商家欺騙的安全措施，因為它們使用證書，來驗明各方的身份。當一方進行交易時，它向涉及的另一方提交證書。證書附著在電子報文上，用于驗明另一方身份，并向接收方提供對回答進行編碼的

99、手段。</p><p>　　另外，信用卡持有人的敏感信息一般保存在金融機構內，由于金融環(huán)境通常提供最高等級的安全性，因而這又是一種額外的安全措施。</p><p>　　但是即使錢包提供了方便的網上購物，尚未被廣泛采用。</p><p>　　標準化是數字錢包能否成功的關鍵。</p><p><b>　　新的無線局域網標準</b&

100、gt;</p><p>　　有了便攜式和無線局域網，用戶在離開其辦公桌的時候，不管是在會議室、公共區(qū)域還是在遠處辦公室，都能享有更高的生產效率。</p><p>　　然而，時至今日，無線局域網對多數企業(yè)應用來說還是太慢。依據IEEE802.11標準，他們運行速度為1兆至2兆位/秒。</p><p>　　現(xiàn)在對此標準的一個新的更高速擴展，能讓無線網支持高達11兆位/秒