徐秀兰编著：紧跟技术动态的计算机通信专业英语教材

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《计算机与通信专业英语》由徐秀兰主编，是一部专为计算机与通信专业学生以及相关工程专业的学生设计的英语教材。本书的特点在于其丰富的内容和语言多样性，它主要取材自上世纪90年代后期的40多种最新外语资料，确保了教材内容紧跟时代和技术发展潮流。书中不仅涵盖了计算机与通信专业所需的基础理论知识，还关注了近年来公众关注的热点话题和技术革新，包括专业术语、常用词组以及科技语法规则。作者特别注重实用性，除了正文之外，教材中包含大量的关键字、注释、习题和部分参考译文，帮助读者深入理解和掌握知识。对于复杂的语法现象，不仅提供翻译，还进行深入解析，便于学习者的自我理解和应用。此外，书后还附有习题解答和生词表，方便读者随时查阅和复习。该书不仅适合计算机与通信专业的学生作为教材使用，也适用于其他工程专业和技术人员进行自我学习和参考。自1995年首版以来，经过多次修订和重印，反响良好，多次被评为优秀教材，并受到了读者的热烈欢迎。在修订过程中，编者始终保持着严谨的态度，力求更新内容，反映最新的技术动态，以满足读者不断增长的需求。总体来说，《计算机与通信专业英语》是一部集学术性、实用性和时效性于一体的高效学习工具，对于提升专业人员的英语能力和专业知识具有重要意义。

general, the room ignores spoken utterances from the lapel microphones not specifically directed to it .”

This is an important simplifying assumption that makes implementation tractable, but it also defines the

smartness of the space in terms of human－computer interaction: the capability of the space to understand

what people are trying to tell it .

Ⅱ .Hardware Prototypes

New hardware systems design for pervasive computing has been oriented towards experimental plat－

forms for systems and applications of invisibility . New chips have been less important than combinations of

existing components that create experimental opportunities . The first pervasive computing technology to be

deployed was the Liveboard [ Elrod 92 ] , which is now a Xerox product . Two other important pieces of pro－

totype hardware supporting our research at PARC are the Tab and the Pad .

Tab

The ParcTab is a tiny information doorway . For user interaction it has a pressure sensitive screen on

top of the display, three buttons underneath the natural finger positions, and the ability to sense its position

within a building . The display and touchpad it uses are standard commercial units .

The key hardware design problems in the pad are size and power consumption . With several dozens of

these devices sitting around the office , in briefcases, in pockets, one cannot change their batteries every

week . The PARC design uses the 8051 to control detailed interactions, and includes software that keeps

power usage down . The major outboard components are a smll analog/ digital converter for the pressure sen－

sitive screen, and analog sense circuitry for the IR receiver . Interestingly, although we have been ap－

proached by several chip manufacturers about our possible need for custom chips for the Tab, the Tab is not

short of places to put chips . The display size leaves plenty of room, and the display thickness dominates

total size . Off－the－shelf components are more than adequate for exploring this design space, even with our

severe size, weight , and power constraints .

A key part of our design philosophy is to put devices in everyday use, not just demonstrate them . We

can only use techniques suitable for quantity 100 replication, which excludes certain things that could make

a huge difference, such as the integration of components onto the display surface itself . This technology,

being explored at PARC, ISI, and TI, while very promising, is not yet ready for replication .

The Tab architecture is carefully balanced among display size , bandwidth, processing, and memory .

For instance, the small display means that even the tiny processor is capable of four frame/ sec video to it ,

and the IR bandwidth is capable of delivering this . The bandwidth is also such that the processor can actu－

ally time the pulse widths in software timing loops . Our current design has insufficient storage, and we are

increasing the amount of non－volatile RAM in future tabs from 8k to 128k .The tab’s goal of postit－note－like

casual use puts it into a design space generally unexplored in the commercial or research sector .

Pad

The pad is really a family of notebook－sized devices . Our initial pad, the ScratchPad, plugged into a

·9·

Sun SBus card and provided an X－window－system－compatible writing and display surface . This same design

was used inside our first wall－sized displays, the liveboards, as well . Our later untethered pad devices,

the XPad and MPad, continued the system design principles of X－compatibility, ease of construction, and

flexibility in software and hardware expansion .

As I write, at the end of 1992, commercial portable pen devices have been on the market for two

years, although most of the early companies have now gone out of business . Why should a pioneering re－

search lab be building its own such device ? Each year we ask ourselves the same question, and so far three

things always drive us to continue to design our own pad hardware .

First, we need the right balance of features; this is the essence of systems design . The commercial

devices all aim at particular niches, and so balance their design to that niche . For research we need a

rather different balance, all the more so for pervasive computing . For instance, can the device communi－

cate simultaneously along multiple channels ?Does the O .S support multiprocessing ?What about the poten－

tial for high－speed tethering ? Is there a high－quality pen ?Is there a high－speed expansion port sufficient for

video in and out ? Is sound in/ out and ISDN available ? Optional keyboard ? Any one commercial device

tends to satisfy some of these, ignore others, and choose a balance of the ones it does satisfy that optimize

its niche , rather than ubiquitous computing－style scrap computing . The balance for us emphasizes commu－

nication, ram, multi－media, and expansion ports .

Second, apart from balance are the requirements for particular features . Key among these are a pen

emphasis, connection to research environments like Unix, and communication emphasis .A high－speed ( >

64kbps) wireless capability is built into no commercial devices, nor do they generally have a sufficiently

high speed port to which such a radio can be added . Commercial devices generally come with DOS or Pen－

point, and while we have developed in both, they are not our favorite research vehicles because of lack of

full access and customizability .

The third thing driving our own pad designs is ease of expansion and modification . We need full hard－

ware specs, complete 0 .S . source code, and the ability to rip－out and replace both hardware and software

components . Naturally these goals are opposed to best price in a niche market, which orients the documen－

tation to the end user, and which keeps price down by integrated rather than modular design .

We have now gone through three generations of Pad designs . Six scratchpads were built, three

XPads, and thirteen MPads, the latest . The MPad uses an FPGA for almost all random logic, giving ex－

treme flexibility . For instance, changing the power control functions, and adding high－quality sound, were

relatively simple FPGA changes . The MPad has built－in both IR (tab compatible) and radio communica－

tion, and includes sufficient uncommitted space for adding new circuit boards later . It can be used with a

tether that provides it with recharging and operating power and an ethernet connection . The operating sys－

tem is a standalone version of the public－domain Portable Common Runtime developed at PARC

[Weiser 89] .

·01·

Exercises

1 . Fill in the following blanks with proper words or phrases found in the text:

(1) A number of researchers around the world are now working in the pervasive computing

(2) Pervasive computing considers the 　of displays into the everyday physical

world .

(3) Pervasive computing 　that you need not carry anything with you .

(4) Information is now the new 　of the global economy .

(5) A number of committees and researchers are now working on methods of 　

or replacing existing protocols to handle mobility .

(6) Most window systems are not able to open 　windows over a network .

(7) When computation becomes part of the environment , most human－computer interaction will be 　

(8) The context associated with 　space will be created by recording interac－

tion with the space and by importing information from outside .

(9) Currently we only allow automatic interaction when our intent is 　and

when the computer can clearly do the job than we can .

2 . True/ False:

(1) Researches on pervasive computing influence some of the areas of computing science . ( 　 )

(2) Pervasive computing is just a personal or intimate computer with agents doing your bidding .

( 　 )

(3) We require complete access to time－sensitive data, regardless of physical location . ( 　 )

(4) Pervasive computing removes the complexity of new technologies, enables us to be more effi－

cient in our work and leaves us more leisure time . ( 　 )

(5) Getting the computer out of the way is not easy because it is a problem of a property of the

whole context of usage of the machine and the affordances of its physical properties . ( 　 )

(6) For the same reason, pervasive computing was much like a multimedia problem, resulting

from any particular deficiency in the ability to display certain kinds of real time data or inte－

grate them into applications . ( 　 )

(7) All work of pervasive now is concentrating on the mobile infrastructure for wireless network－

ing . ( 　 )

(8) Pervasive computing need for surprisingly wireless bandwidth . ( 　 )

(9) Networking developed for the past twenty years with the assumption that a machine’s name ,

and its network address, were varying . ( 　 )

(10) Our relationship to pervasive computing will differ basically from our current relationship with

computers . ( 　 )

·11·

UNIT 2

Computer Systems

2－1 　 Why Should People Care of a Computer System?

What do the insides of a computer“look like”, and why do we care ?

As users we do not have to know the answer to this question, any more than we have to understand the

workings of a car engine in order to drive the car .

We can run standard software packages without understanding exactly how they work; we can pro－

gram a computer in a high－level language without understanding how the machine executes the individual

instructions; we can purchase a computer system from a salesman without understanding the specifications

of the system .

And yet, there in something missing . Perhaps the package doesn’t do exactly what we want, and we

don’t understand the machine well enough to risk fooling around with the package’s options . Perhaps if we

understood the system, we might have written the program to be faster and more efficient .

　 Perhaps the

salesman did not sell us the optimum system for our job . Or perhaps it’s nothing more than a sense of ex－

citement that’s missing . But that’s important, too !

The jargon of computers has become a part of the English language . You can open any daily newspa－

per and find references to“8MB RAM”of“64－bit PCI Video Accelerator”or“256k cache”in articles and

advertisements . ( In a way, it’s scary !)

You’ll notice that this computer features a 60－MHz Pentium CPU, 8MB of RAM memory, and a 540

megabyte (MB) hard drive, among other things . But how good a system is this ?Are these features impor－

tant to the user ?Is this the right combination of features that you need in your computer to have the com－

puter perform the work that you wish to get done ?

　 Is a 60－MHz Pentium the best choice of a CPU ? Per－

haps we are paying too much for the performance that we need . Or maybe we need more .

What does the presence of a 64－bit PCI video accelerator imply in the context of a long－term invest－

ment of computers for your organization ?What other information about this system would allow you to make

a more informed decision ?

Some of the expressions used in these articles and ads are obvious from the context . Other references

may be more obscure . Presumably, everyone today knows what a“monitor”is . But how many people know

what the terms“cache memory”or“multitasking”or“PCI bus”mean or what their importance is ?Yet all

these expressions have appeared recently in daily newspaper advertisements with the assumption that people

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