A processor is composed of two functional units—a control unit and an arithmetic/logic unit—and a set of special workspaces called registers．

　　1．The Control Unit
   
　　The control unit is the functional unit that is responsible for supervising the operation of the entire computer system．In some ways，it is analogous to a telephone switch-board with intelligence because it makes the connections between various functional units of the computer system and calls into operation each unit that is required by the program currently in operation[2]．
The control unit fetches instructions from memory and determines their types or decodes them．It then breaks each instruction into a series of simple small steps or actions．By doing this，it controls the step-by-step operation of the entire computer system．

　　2．The Arithmetic and Logic Unit
   
　　The arithmetic and logic unit（ALU）is the functional unit that provides the computer with logical and computational capabilities．Data are brought into the ALU by the control unit，and the ALU performs whatever arithmetic or logic operations are required to help carry out the instruction[3]．
　　Arithmetic operations include adding，subtracting，multiplying，and dividing．Logic operations make a comparison and take action based on the results．For example，two numbers might be compared to determine if they are equal．If they are equal，processing will continues；if they are not equal，processing will stop．
   
　　3．Registers
     
　　A register is a storage location inside the processor．Registers in the control unit are used to keep track of the overall status of the program that is running．Control unit registers store information such as the current instruction，the location of the next instruction to be executed，and the operands of the instruction．In the ALU，registers store data items that are added，subtracted，multiplied，divided，and compared．Other registers store the results of arithmetic and logic operations．
　　An important factor that affects the speed and performance of a processor is the size of the registers．Technically，the term word size（also called word length）describes the size of an operand register，but it is also used more loosely to describe the size of the pathways to and from the processor．Currently，word sizes in general purpose computers range from 8 to 64 bits．If the operand registers of a processor are 16 bits wide，the processor is said to be a 16-bit processor．

　　处理器由两个功能部件（控制部件和算术逻辑部件）与一组称为寄存器的特殊工作空间组成。
 　　1．控制部件
    控制部件是负责监控整个计算机系统操作的功能部件。从某些方面看，它类似于智能电话交换机，因为它将计算机系统的各功能部件连接起来，并按当前运行的程序的需要，“传唤”每个部件进行操作。
   　 控制部件从存储器中取出指令，并确定其类型或对其进行译码。然后将每条指令都分解成一系列简单的小步骤或动作。这样，它就控制了整个计算机系统的步进操作。
   　 2．算术逻辑部件
    　算术逻辑部件（ALU）是为计算机提供逻辑及计算能力的部件。控制部件将数据送入算术逻辑部件，然后由算术逻辑部件完成执行指令所需的任何算术或逻辑运算。
   　 算术运算包括加、减、乘、除。逻辑运算进行比较，并根据比较结果采取“行动”。例如，可以比较两个数是否相等，如果相等，则继续处理；如果不等，则停止处理。
    　3．寄存器
    　寄存器是处理器内的存储单元。控制部件中的寄存器用来跟踪正在运行的程序的总体状态。控制器寄存器存储如当前指令、下一条将要执行的指令地址以及该指令的操作数等信息。在算术逻辑部件中，寄存器存放要进行加、减、乘、除及比较的数据项。而其他寄存器则存放算术和逻辑运算的结果。
    　影响处理器速度和性能的一个重要因素是寄存器的大小。从技术上讲，术语“字长”描述了操作数寄存器的大小，但它也可用于不那么严格地描述出入处理器的通道的大小。现在，通用计算机的字长从8位到64位不等。如果处理器的操作数寄存器是16位的，那么就称该处理器是16位处理器。