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景德镇瓷业帮规农历（）月（），（）行业规定这天停工。

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（）是樟树药帮的组织。

江右商帮行会制度是传统（）的重要组成部分。

Computer DesignDatapathsThe term datapath refers to a series of devices that perform calculations. A control distributes program instructions to the datapath, memory, and I/O devices. We discussed control units previously in Chapters 1 and 3. Standard datapaths consist of a PC (program counter) and various small registers. Arithmetic logic units (ALUs) and simple adders perform （ 1 ） arithmetic tasks. In some cases, there are multiple adders and ALUs performing calculations simultaneously. However, it is impractical to wire every possible I/O （ 2 ）. Many datapaths solve this problem with a multiplexer, or data （ 3 ）. Multiplexers transfer data from the correct input source to its destination.The address of the current instruction is stored in an instruction register. Be careful not to confuse the （ 4 ） register with the PC. The PC stores the address of the next planned instruction,like a bookmark.In order to understand implementation,we must understand the three instruction classes:memory-reference instructions read from memory or write data to （ 5 ）arithmetic-logical instructions perform calculationsbranch instructions provide the PC with a new instruction addressNote that all three instruction classes make use of ALUs! Don't let the term 'arithmetic-logical' fool you.

Datapath ImplementationStudent: Hi, Professor Curtis? I'm a little confused about （1） implementation. Do you have time to help me?Instructor: Sure, Angela. Come on in. What's confusing you?Student: Well, I know that the control gives （2）. But I don't really understand the data flow.Instructor: Like you said, the （3） gives instructions to the datapath. Do you know what the first step is?Student: No, I don't.Instructor: Take a guess.Student: Is it having the PC fetch the next instruction?Instructor: That's right. See, you understand better than you think you do. From there, we usually have to follow a memory-reference instruction.Student: Okay. Then what?Instructor: Well, all instruction classes use the （4）. So that's where the data goes next.Student: All of them? I thought it was just for arithmetic-logical instructions.Instructor: I know why you might think that, but it's not the case. After that, it's a matter of sending the （5） to the right destination. Does that make sense?