1. 下列說法正確的是 （ ）
A. Java語言不區(qū)分大小寫
B. Java程序以類為基本單位
C. JVM為Java虛擬機(jī)JVM的英文縮寫
D. 運(yùn)行Java程序需要先安裝JDK
2. 下列說法中錯(cuò)誤的是 ( )
A. Java語言是編譯執(zhí)行的
B. Java中使用了多進(jìn)程技術(shù)
C. Java的單行注視以//開頭
D. Java語言具有很高的安全性
3. 下面不屬于Java語言特點(diǎn)的一項(xiàng)是( )
A. 安全性
B. 分布式
C. 移植性
D. 編譯執(zhí)行
4. 下列語句中，正確的項(xiàng)是 ( )
A . int $e,a,b=10
B. char c,d=’a’
C. float e=0.0d
D. double c=0.0f
Without doubt, the age of information communications is upon 11s. The rapid
pace of technological advancement in digital data communications can be wit-
nessed in a multitude of applications in our day-to-day existence. In recent
years, the widespread proliferation of wireless digital cornmunications hass been
readily accepted by the general population worldwide; this is nearly unpa~rallcled
in few other human scientific achievements in terms of scope and speed of devel-
opment.
This guide explains how data networks operate, why data systems are becoming more complicated, and how data networks are changing to permit broadband services and applications.
Table of Contents
Introduction To Data Networks—PDN, LAN, MAN, WAN, and Wireless Data, Technologies and Systems
Data Networks
List of Figures
With the rapid growth of the wireless mobile applications, wireless voice has
begun to challenge wireline voice, whereas the desire to access e-mail, surf the
Web or download music (e.g., MP3) wirelessly is increasing for wireless data.
While second generation (2G) cellular wireless systems, such as cdmaOne1,
GSM2 and TDMA3, introduced digital technology to wireless cellular systems
to deal with the increasing demand for wireless applications, there is still the
need for more spectrally efficient technologies for two reasons. First, wireless
voice capacity is expected to continue to grow. Second, the introduction of
high-speed wireless data will require more bandwidth.
Once upon a time, cellular wireless networks provided two basic services: voice
telephony and low-rate text messaging. Users in the network were separated
by orthogonal multiple access schemes, and cells by generous frequency reuse
patterns [1]. Since then, the proliferation of wireless services, fierce competition,
andthe emergenceof new service classes such as wireless data and multimediahave
resulted in an ever increasing pressure on network operators to use resources in a
moreefficient manner.In the contextof wireless networks,two of the most common
resources are power and spectrum—and, due to regulations, these resources are
typically scarce. Hence, in contrast to wired networks, overprovisioning is not
feasible in wireless networks.
特點(diǎn)(FEATURES) 精確度0.1%滿刻度 (Accuracy 0.1%F.S.) 可作各式數(shù)學(xué)演算式功能如:A+B/A-B/AxB/A/B/A&B(Hi or Lo)/|A| (Math functioA+B/A-B/AxB/A/B/A&B(Hi&Lo)/|A|/etc.....) 16 BIT 類比輸出功能(16 bit DAC isolating analog output function) 輸入/輸出1/輸出2絕緣耐壓2仟伏特/1分鐘(Dielectric strength 2KVac/1min. (input/output1/output2/power)) 寬范圍交直流兩用電源設(shè)計(jì)(Wide input range for auxiliary power) 尺寸小,穩(wěn)定性高(Dimension small and High stability)
