单项选择题 For each blank, choose the best answer from the four choices and write down on the answer sheet.(21)is a six bytes OSI layer 2 address which is burned into every networking evice 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.

单项选择题 SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietion of the(71)protocol called NRM is essentially the same as SDLC. SDLC is(72) protocol like HDLC, Frame. Relay or X.25.An SDLC network is made up of(73)that controls all communications, and(74). It is capable of(75)operation, but almost all practical applications are strictly half duplex.

单项选择题 Multipurpose Internet Mail Extension (MIME) is a(46)document messaging standard in the Internet enviroment, with MIME, users can send(47)Email messages that include audio, video, graph-ices, and text to any other user of a TCP/IP network. Richtext information can also be(48)into messages. It defines the fonts, formats, and(49)features of a document so the document can be easily(50)on many different types of systems.

单项选择题 计算机指令系统中采用不同寻址方式的主要目的是(3)。在下列寻址方式中，取操作数速度最慢的是(4)。

单项选择题 已知X=-73，若采用8位机器码表示，则[X]原=(1)，[X]补=(2)。