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?
现阶段没有创业意愿的同学还需要接受创业教育的主要原因是( )。
A. 方便找工作
B. 创新能力与创新精神是现代大学生应该具备的基本素养
C. 防止失业后找不到工作
D. 创业基础是必修课
下列选项中属于创业者面临的内部因素的是( )。
A. 市场准入制度
B. 消费者购买力
C. 融资难度
D. 创业者实践经验