MIDI enables people to use 1 computers and electronic musical instruments. There are actually three components to MIDI, the communications" 2 .", the Hardware Interface and a distribution 3 called "Standard MIDI Files". In the context of the WWW, the most interesting component is the 4 Format. In principle, MIDI files contain sequences of MIDI Protocol messages. However, when MIDI Protocol 5 are stored in MIDI files, the events are also time-stamped for playback in the proper sequence. Music delivered by MIDI files is the most common use of MIDI today.
Spread spectrum simply means that data is sent in small pieces Over a number of the 6 frequencies available for use at any time in the specified range. Devices using 7 spread spectrum (DSSS) communicate by 8 each byte of data into several parts and sending them concurrently on different 9 . DSSS uses a lot of the available 10 , about 22 megahertz (MHz) .
11 is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group. 12 is an error detection code that most data communication networks use. 13 is an interior gateway protocol that uses a distance vector algorithm to propagate routing information. 14 is a transfer mode in which all types of information are organized into fixed form cells on an asynchronous or non-periodic basis over a range of media. 15 is an identifier of a web page.
Networks can be interconnected by different devices. In the physical layer networks can be connected by 16 or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches which operate at data link layer. They can accept 17 , examine the MAC address and forward the frames to a different network while doing minor protocol translation in the process. In network layer, we have routers that can connect two networks. If two networks have 18 network layer, the muter may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message 19 . As an example, gateways between Internet e-mail and X.400 e-mail must 20 the e-mail message and change various header fields.
21 is a six bytes OSI layer 2 address which is burned into every networking device that provides its unique identity for point to point communication. 22 is a professional organization of individuals in multiple professions which focuses on effort on lower-layer protocols. 23 functions with two layers of protocols. It can connect networks of different speeds and can be adapted to an environment as it expands. 24 is the popular LAN developed under the direction of the IEEE802.5. 25 is the popular backbone technology for transmitting information at high speed with a high level of fault tolerance which is developed under the direction of ANSI.
21.
A.The MAC address
B.The IP address
C.The subnet address
D.The virtual address
A B C D
A
22.
A.ISO
B.ANSI
C.CCIT
D.IEEE
A B C D
D
23.
A.The hub
B.The bridge
C.The router
D.The proxy
A B C D
B
24.
A.Ethernet
B.Token Bus
C.Token Ring
D.DQDB
A B C D
C
25.
A.X.25
B.ATM
C.FDDI
D.SMDS
A B C D
C
[解析] (1)MAC地址(The MAC address)是一个位于OSI第二层的六位地址。它被内置到每个网络设备里，以给每个点对点的通信提供惟一的标识。 (2)IEEE是一个专业组织，它由多个领域内的专业人士组成，主要致力于低层协议。 (3)网桥(The bridge)的功能涉及两层协议。它可以连接不同速度的网络，也可以适应扩展的环境。 (4)令牌环网(Token Ring)是根据IEEE802.5标准开发的流行的局域网。 (5)FDDI是高速传输信息的流行的骨干技术，并具有高度的容错性，它是在ANSI的指导下开发的。
Melissa and Love Letter made use of the trust that exists between friends or colleagues. Imagine receiving an 26 from a friend who asks you to open it. This is what happens with Melissa and several other similar email 27 . Upon running, such worms usually proceed to send themselves out to email addresses from the victim's address book, previous emails, web pages 28 . As administrators seek to block dangerous email attachments through the recognition of well-known 29 , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to .bat and .cmd plus a whole list of other extensions and will still run and successfully infect target users. Frequently, hackers try to penetrate networks by sending an attachment that looks like a flash movie, which while displaying some cute animation, simultaneously runs commands in the background to steal your passwords and give the 30 access to your network.
Originally introduced by Netscape Communications, 31 are a general mechanism which HTFP Server side applications, such as CGI 32 , can use to both store and retrieve information on the HTTP 33 side of the connection. Basically, Cookies can be used to compensate for the 34 nature of HTTP. The addition of a simple, persistent, client-side state significantly extends the capabilities of WWW-based 35 .
The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable 36 of the technical requirements for the software product. During the requirements definition phase, the requirements definition team uses an interative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform and each 37 that it must meet. The starting point is usually a set of high level requirements from the 38 that describe the project or problem. In either case, the requirements definition team formulates an overall concept for 'the system and then defines 39 showing how the system will be operated, publishes the system and operations concept document and conducts a system concept review (SCR) . Following the SCR, the team derives 40 requirements for the system from the high level requirements and the system and operations concept using structured or object-oriented analysis. The team specifies the software functions and algorithms needed to satisfy each detailed requirement.
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