Unit 14 Data CommunicationContentsLearning ObjectivesAfter you have re
ad this unit, you should be familiar with:1. The types of data co
mmunication2. The functions that hardware devices in the data com
munications Words&ExpressionsText How do we send messages to a
nother person? For the sender to pass a message to another person
, the sender must encode the message in a form that can be transm
itted. The received message must be in an encoded form that can b
e decoded and understood by the recipient. Miscommunication can o
ccur at any one of these steps. For computers to communicated and
share data or programs, these same steps must be followed and po
tential pitfalls avoided.Before looking at how computers and peri
pherals are joined into powerful systems, let''s define two terms:
data communications and networks. Data communications is the tra
nsmission, reception, and validation of data. With data communica
tions, processing is performed by a great, such as from the West
Coast to the East Coast, or small, suchTextas between two floors
of the same building. Even smaller yet, the links between a compu
ter and its peripherals is also data communications. Other terms
for data communications include teleprocessing and telecommunicat
ions. To avoid confusion we will stick to the term data communica
tions for this chapter. Networks are a combination of computer
s and peripherals linked together for the purpose of data communi
cations. Data communications networks can be simple or complex, l
arge or small. The idea behind any data communications system, ho
wever, is simple: the different hardware elements of an informati
on system are linked together by some medium. Data travel from on
e point to another within the system and are processed. Even a mi
crocomputer, which has its keyboard, disk drives, and displayscre
en built into a single cabinet with the computer, links the diffe
rent components through an internal data communications medium. T
he microcomputer is not a true data communications network since
everything is right there in one spot. Data communications pro
vides rules that allow computers with different operating systems
, languages, cabling and locations to share resources. Many appli
cations are served by data communications networks. A computer in
a police squad car can be linked to the police department’s cent
ral dispatch computer. Spaceships and their ground stations are l
inked in data communications networks responsible for bringing ba
ck human beings and equipment intact. Microcomputers can use d
ata communications networks for sending e-mail, conversing with e
ach other across the nation instantly, and holding remote meeting
etc. their link to the world of data communications networks in
a plain old telephone. The information system element, hardwar
e, can be divided into local user hardware, the host processor, a
nd communications devices. Local user hardware can consist of one
or more peripheral devices such as display terminal, printers, a
nd secondary storage units. The hardware can also consist of a co
mputer any size. The function of local user hardware is to transm
it data to a computer elsewhere in the data communications networ
k for processing, or to receive data from this other computer. If
local user hardware is itself a computer, it can also beused to
perform local information processing independent of the network.
The host processor is the computer to which the local user har
dware is connected, and which does the actual processing of data.
In some networks, a computer can serve simultaneously as a host
processor for distant users, and a local processor for nearby use
rs. Networks may have more than one host processor, or do without
the host. The communications devices link the local user hard
ware with the host processor. There are two types of communicatio
ns devices: switching equipment and media. Communications switchi
ng equipment serves as the intermediary between local user hardwa
re and data communications media, such as switches, hubs, and rou
ters. Data communications media handle the actual transmission of
data between local user hardware andthe host processor. There ar
e a number of different transmission media, including copper wire
s, coaxial cables, fiber-optic cables, communication satellites,
and microwave radio. Data communications networks can help sup
port time-sharing, real time processing, batch processing, or a c
ombination of the three. Batch processing occurs when data are co
llected over a period of time and processed as a group. With time
-sharing processing the computer alternates between several opera
tions and allows many users to share at the same time, the same c
omputer. Real-time processing handles data fast enough that the r
esults can be used to influence a process that is still taking pl
ace.Exercises1. Answer the following question according to the t
ext.(1) What is data communication?(2) Why must we encode before
transmit the information?(3) Why is not the microcomputer a true
data communications network?(4) What does the information system
include?2. Translate the following terms or phrases from English
into Chinese and vice versa:key3. Fill in the blanks with the i
nformation given in the text: (1) Before looking at how computers
and peripherals are joined into powerful systems, let''s define t
wo terms: and . Data communications is the ,
, and .(2) Networks are a combination of and
linked together for the purpose of . Data communications n
etworks can be simple or , large or .(3) Data communi
cations provides rules that allow computers with different
, , and to share resources..(4) The informati
on system element, hardware, can be divided into , a
nd .(5) The communications devices link the local user hard
ware with the host processor. There are two types of communicatio
ns devices: and .key4. Choose the best one from the
items given below to complete the following passage. Spywa
re and other forms of malware are the biggest online threat to yo
ur computer’s (1) nowadays. These malicious (2) which get
to your PC through freeware, shareware, commercial sites, decept
ive pop-ups or in any other way, can record your surfing habits a
nd sites you visit, share your personal information which their p
artners. Any personal (3) , when in wrong hands, can leave yo
u a victim of an “identity theft” by steeling your credit (4)
details, birth records and other (5) information.(1) A. re
liability B. security C. capability D. efficiency(2) A. hardware
B. cards C. programs D. equipment(3) A. information B. state
C. life D. existence(4) A. reputation B. password C. address D
. card(5) A. public B. confidential C. open D. comme
rcialkey5. Mark the following statements with T(true) or F(false
) according to the text.(1) For the sender to pass a message to
another person, the sender must encode the message in a form that
can be transmitted.(2) The microcomputer is a true data communi
cations network since everything is right there in one spot.(3)
Local user hardware can consist of one or more peripheral devices
such as display terminal, printers, and secondary storage units.
(4) Communications switching equipment serves as the intermediar
y between local user hardware and data communications media, such
as switches, hubs, and routers.(5) With batch processing the co
mputer alternates between several operations and allows many user
s to share at the same time, the same computer.key6. Select the
one answer to each question.(1) is a device that converts i
mages to digital format.A. Copier B. Printer C. Scanner D. Dis
play (2) are those programs that help find the information
you are trying to locate on the WWW.A. Window B. Search Engines
C. Web Site D. Web Pages(3) What is the purpose of logical addre
sses in an IP network? A. They are used by switches to make
forwarding decisions. B. They are used to determine which host de
vice accepts the frame. C. They provide vendor-specific informati
on about the host. D. They are used to determine the network that
the host is located on.(4) Most measures involve data encr
yption and password.A. security B. hardware C. display D. pro
gram(5) A is a functional unit that interprets and carries
out instructions.A. memory B. processorC. storage D. network(
6) In , the only element that can be deleted or removed is
the one that was inserted most recently.A. a line B. a queueC
. an array D. a stackkey7. Translate the following sentences
into Chinese.(1) Before looking at how computers and peripherals
are joined into powerful systems, let''s define two terms: data c
ommunications and networks. Data communications is the transmissi
on, reception, and validation of data.(2) The idea behind any dat
a communications system, however, is simple: the different hardwa
re elements of an information system are linked together by some
medium. Data travel from one point to another within the system a
nd are processed.(3) Data communications media handle the actual
transmission of data between local user hardware and the host pro
cessor. There are a number of different transmission media, inclu
ding copper wires, coaxial cables, fiber-optic cables, communicat
ion satellites, and microwave radio.(4) With time-sharing process
ing the computer alternates between several operations and allows
many users to share at the same time, the same computer. Real-ti
me processing handles data fast enough that the results can be us
ed to influence a process that is still taking place.key1.略2.3. (
1) data communications，networks，transmission，reception，validation of data (2) computers，peripherals，data communications，complex，small (3) operating systems，languages，cabling，locations (4) local user hardware，he host processor，communications devices. (5) switching equipment, media4. (1) B (2) C (3) A (4) D (5) B5.(1) T (2) F (3) T (4) T (5) F6. (1) C (2) B (3) C (4) A (5) B (6) D7.(1) 在研究如何计算机和外围设备参与了强大的系统之前，让我们定义两个术语：数据通信和网络。数据通信是传输，接收和数据验证。 (2) 然而，任何数据通信系统背后的思想是很简单的：一个信息系统的不同硬件部分由一些媒介连接起来，数据从系统内的一点传送到另一点并被处理。 (3) 数据通信媒体处理本地用户硬件和主处理器之间的实际数据传输。有许多不同的传输媒介，包括铜线，同轴电缆，光缆，通信卫星和微波。 (4) 计算机使用分时处理在数次操作和允许多个用户同时在同一台计算机上共享资源之间交替进行。实时处理数据的处理速度足够快，结果可以用来影响目前仍在发生的进程。 |
|
