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1.3 / KEY TERMS AND REVIEW QUESTIONS 15

interconnection is by means of a system bus, consisting of a number of con-
ducting wires to which all the other components attach.
There may be one or more of each of the aforementioned components. Tradi-
tionally, there has been just a single processor. In recent years, there has been in-
creasing use of multiple processors in a single computer. Some design issues relating
to multiple processors crop up and are discussed as the text proceeds; Part Five
focuses on such computers.
Each of these components will be examined in some detail in Part Two. How-
ever, for our purposes, the most interesting and in some ways the most complex
component is the CPU. Its major structural components are as follows:

• Control unit: Controls the operation of the CPU and hence the computer
• Arithmetic and logic unit (ALU): Performs the computer’s data processing
functions
• Registers: Provides storage internal to the CPU
• CPU interconnection: Some mechanism that provides for communication
among the control unit,ALU, and registers
Each of these components will be examined in some detail in Part Three, where we
will see that complexity is added by the use of parallel and pipelined organizational
techniques. Finally, there are several approaches to the implementation of the con-
trol unit; one common approach is a microprogrammed implementation. In essence,
a microprogrammed control unit operates by executing microinstructions that define
the functionality of the control unit. With this approach, the structure of the control
unit can be depicted, as in Figure 1.4.This structure will be examined in Part Four.

1.3 KEY TERMS AND REVIEW QUESTIONS

Key Terms

arithmetic and logic unit computer organization processor
(ALU) control unit registers
central processing unit (CPU) input–output (I/O) system bus
computer architecture main memory

Review Questions

1.1. What, in general terms, is the distinction between computer organization and com-
puter architecture?
1.2. What, in general terms, is the distinction between computer structure and computer
function?
1.3. What are the four main functions of a computer?
1.4. List and briefly define the main structural components of a computer.
1.5. List and briefly define the main structural components of a processor.