WHAT IS A PROCESSOR* t6 s$ N/ Z7 F# H
   
" R9 b2 S5 ?# ^' E1 F6 G( i) Z　　A processor is a functional unit that interprets and carries out instructions．Every processor comes with a unique set of operations such as ADD，STORE，or LOAD that represent the processor’s instruction set． Computer designers are fond of calling their computers machines[1]，so the instruction set is sometimes referred to as machine instructions and the binary language in which they are written is called machine language！You shouldn’ t confuse the processor’s instruction set with the instructions found in high-level programming languages，such as BASIC or Pascal．　　An instruction is made up of operations that specify the function to be performed and operands that represent the data to be operated on．For example，if an instruction is to perform the operation of adding two numbers，it must know（1）what the two numbers are and（2）where the two numbers are．When the numbers are stored in the computer’s memory，they have their addresses to indicate where they are．So if an operand refers to data in the computer’ s memory it is called an address．The processor’ s job is to retrieve instructions and operands from memory and to perform each operation．Having done that，it signals memory to send it the next instruction.
( W7 I3 W% w% X1 i. B0 j) ^0 F　　This step-by-step operation is repeated over and over again at awesome speed．A timer called a clock releases precisely timed electrical signals that provide a regular pulse for the processor’ s work．The term that is used to measure the computer’ s speed is borrowed from the domain of electrical engineering and is called a megahertz（MHz），which means million cycles per second．For example，in an 8-MHz processor，the computer’ s clock ticks 8 million times to every 1 second tick of an ordinary clock．
3 [3 e5 \! m! v: m! Z( ^- e9 @/ N　　 什么是处理器
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+ a" |" O; W7 [9 f: I; {# G% D/ P+ z　　处理器是解释并执行指令的功能部件。每个处理器都有一个诸如ADD、STORE或LOAD之类的特有*作集，这个*作集就是该处理器的指令系统。计算机系统设计者习惯将计算机称为机器，所以该指令系统有时也称为机器指令系统，而书写指令的二进制语言叫做机器语言！注意，不要将处理器的指令系统与BASIC或PASCAI这样的高级程序设计语言中的指令系统相混淆。
' W+ W  q# ]9 W　　指令由*作码和*作数组成，其中*作码规定要完成的*作功能，*作数则表示所*作的数据。例如，一条指令要完成两数相加的*作，它就必须知道：（l）这两个数是什么，（2）这两个数在哪儿。当这些数存储在计算机内存中时，有指明其位于何处的地址。所以，如果*作数用来指引计算机内存中的数据，则该*作数叫做地址。处理器的工作就是从存储器中取出指令和*作数，并执行每一*作。处理器完成这些工作后就通知存储器送来下一条指令。9 J0 C1 ^0 a5 ]5 B) m& [
　　这种步进*作以惊人的速度一遍又一遍地重复。一个称为时钟的计时器准确地发出定时电信号，为处理器工作提供有规律的脉冲。测量计算机速度的术语是从电工领域借用来的，称为兆赫（MHz），指每秒百万个周期。例如，普通时钟每秒滴答一次，而在8MHz的处理器中，计算机的时钟每秒滴答800万次。

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 Unit6 I4 P& v4 j) {4 z" P* x
   
3 Y; W3 [/ z! @9 e8 {　　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]．
+ D% v! j- ~9 t' S: C3 |. ]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．$ |4 e9 }, N+ C9 X. V) _1 P1 m+ q
　　2．The Arithmetic and Logic Unit
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' o1 W6 V/ A4 B0 ^　　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]．0 X9 u$ J; ?! F7 q5 ?
　　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．4 y7 Q4 I5 M' _
   
5 E/ |+ L( n1 P1 i　　3．Registers* m8 I, [1 K2 L8 [+ K
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　　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．! d% W/ {* I* G# n
　　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．8 b( B' o5 W- C; u
　　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。( f+ {3 D9 I, A2 U; q: h
　　1．控制部件( L& y% e0 O) X& |4 m! {
    控制部件是负责监控整个计算机系统*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*作。
- f1 V4 k  X5 P: y$ {& h   　 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*作。
' B. m2 \4 a8 A9 I% w   　 2．算术逻辑部件7 ]  f. w- H6 \
    　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。: P# J* x' Z& u' n8 Z
   　 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。8 r1 F7 o8 `& w* @. n; T9 O
    　3．寄存器
, B/ N: V, ~3 {; R% @2 y: s    　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*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。: C! c9 D" F- U2 d0 Z% u, d
    　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*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*作数寄存器是16位的，那么就称该处理器是16位处理器。

NOTES
' C8 w) R" Y& A　　[1]  be fond of doing…是短语“乐于……，喜欢……”；call computers machines意为“把计算机称为机器”。# w  A2 b2 b( C4 Z2 B, S
　　[2] because后的原因状语从句，由makes和calls带出的两个并列分句组成。Calls into operation each unit中的双宾语倒装，正常语序为calls 　　each unit into operation。原意为“传唤各部件进行*作”，这里指微*作，实际上是指“完成微*作”。7 |- H1 M5 z) ?: X
　　[3] 这是一个and连接的并列句。后一个分句中的whatever是关系代词，引导后面的宾语从句。 　　KEYWORDS7 s. N: R8 I. j$ I
　　instruction        指令      * d/ L: V8 g, @, c8 ~4 u
　　clock                时钟
+ \8 Q3 ^/ {, F* q8 c　　instruction set        指令系统，指令集   
' Q, r) u" c6 M8 D- X, ]/ r　　megahertz（MHz）        兆赫1 a9 K8 f3 p3 o- b6 \/ p
　　processor        处理器     1 k- F. w$ m- x0 f: u0 N/ O* H" E
　　control unit        控制器，控制部件
/ O1 A7 u, x' B4 k2 W0 E7 F　　operation        *作、*作码、*作码指令
# J# z* M: q2 D( B4 D* V1 M/ G4 ]　　arithmetic and logic unit（ALU）算术/逻辑部件
- [) _4 y/ R" j' |" Y　　operand         *作数     * H: |+ i1 L1 \. k4 @% `. m/ ?
　　word size（word length)字长
% E& M# ~$ {/ S0 [　　register        寄存器     0 d! l* ~, W: T8 `; f
　　machine Ianguage       机器语言
& P9 }- x% J+ C  c( @　　EXERCISES
9 C4 T5 v1 a' i$ t1 w* H　　1．Match the following terms to the appropriate definition．% v+ }- N: u7 x" |5 ?2 r$ e; h
　（1）_____ Processor．   
) i+ s$ |" p6 X8 A' k( P　（2）_____ Instruction set．
6 P. D4 A% _$ M0 h　（3）_____Clock．   
1 u7 t% @7 q6 |0 u9 L' o　（4）______Machine language.      
8 n( Y0 q6 X  X/ y9 b7 h- x; m/ ]　（5）______Operation．   
4 M! R0 L% M% K/ _' Q　（6）______Operand．/ Q* J8 w8 g  Q
　（7）______Megahertz（MHz）．  c8 v9 d- l5 l# _8 a. `( D+ h3 [
　（8)______Control unit．
( J. O: h! Q1 A- T7 z　（9）______Arithmetic and logic unit（ALU）．
2 q' s4 T1 W3 m2 w  I7 G& W. H　（10______Register．
5 \1 t+ E- q/ I; C7 W　（11______Word size．
, U1 W% g+ |0 M) G2 Z! f　　a．The part of an instruction that specifies the function that is to be performed．
$ n) B9 n- K& T% n1 n3 `, s& {　　b．The binary language in which a computer’s instruction set is written．1 k) x- @: ^, u6 W, \5 C: _
　　c． A timer in a processor that releases precisely timed signals that provide a pulse for the processor’ s work．1 |( z7 ~; D9 k+ c' m+ I
　　d．A functional unit that interprets and carries out instructions．& H- K9 I+ W  d& _0 H2 n( [* q$ ]
　　e．A unique set of operations that comes with every processor．6 v2 j. o$ c/ Q
　　f．The part of an instruction that tells where data that are operated on are located．
- n9 [  Y1 A8 j' u5 I5 ]　　g．Million cycles per second．
8 C6 z' D6 W; S' c  B6 j　　h．The function unit that is responsible for supervising the operation of the entire computer system．# q0 H; T& X5 i' L1 |/ X- l6 ~" h
　　i．A function unit that provides the computer with logical and computational capability．$ l( `4 a4 O9 o& F+ _6 z- N% I
　　j．The term used to describe the size of operand registers and buses．
# C  _& v6 l5 n　　k．A storage location inside the processor．- X2 q2 e9 z3 |* b, Z, S+ p! }
　　2．Fill in the blanks with appropriate words or phrases$ u8 l) c2 g+ i* k* i  u$ f
　（1）We usually call our computers ______．
! Y  M  q: L( O( Q. c　（2）An instruction set can sometimes be referred to as ______．
. O# {. \  L4 A  o　（3）The binary language is called ______．
+ `3 N: ]% D, C6 b  {" {　（4）We don’t confuse the processor’s instruction set with the instructions of ______．
' ^9 O) v' F* r! W+ Z0 _/ R　（5）An instruction consists of ______．$ F9 \" N7 T3 S' G
　（6）An operand that refers to data in the memory is called an______ ．
4 N* S/ F7 v  d/ k　（7）A timer can give precisely timed ______．- Y: c, W% B6 E$ H- n# d
　（8）A processor includes two functional units，they are ______．
4 L9 s+ ]' z, t$ _9 N) t. b0 I　（9）The ways by which the control unit works are analogous to______．
/ u6 a  u' s' S* T7 e8 }　（10）The control unit takes out the ______from memory．
0 q' ~% m8 v1 _　　a．address         b．high-level programming languages6 S+ s6 z6 h+ A% b
　　c．instructions         d．machines
5 O2 }3 z1 l6 v" D　　e．electrical signals        f．machine instructions3 g; f' i* C9 l7 C# H. T
　　g．a telephone switch-board with intelligence  h．operations and operands
3 N, B" x+ r% g4 j* m8 I, B3 [7 |　　i．machine language       j．control unit and ALU/ u, i: ]) O8 O9 \4 j3 }# f7 H: D' b
　　1．（1）d  （2）e （3）c  （4）b（5）a  （6）f  （7）g（8）h（9）i （10）k （11）j& D. T9 [2 R# Y7 |: w
　　2．（1）d  （2）f  （3）i  （4）b（5）h  （6）a  （7）e （8）j（9）g （10）c