1.4 A Plan of Attack

 The basic building block of a modern

computer is a chip, a complex, integratedelectronic circuit etched on a tiny squareof silicon no bigger than a fingernail.

Since loose chips are fragile and difficuitto handle,they are normally packaged andmounted on boards.

Acomputer is assembled by slidingthe appropriate boards into a cabinet.one board might hold the processor.Another might hold main memory.while a third might contain the

electronics to link a particular input oroutput device to the system.

1.3 How a Computer Works

Let's use the system pictured in Fig 1.4to illustrate how a typical computerworks. Acomputer is controlled by astored program;thus, the first step inusing the machine is copying the

program from diskette into memory.

Now, the processor can begin

executing instructions. lnput datafrom the keyboard are stored inmemory. The processor

manipulates the data, storing theresuts back into memory- Finally,the resulits are output.

Memory's contents are easy to change.Thus, when one set of data has been

processed, the program can be repeated,reading and processing new data, and

generating new output. If the data can bechanged, why not the program? When aprogram is finished, a new one can take itsplace in memory,allowing the computer toProcess complete different data..

One minute it can generate

paychecks from labor data undercontrol of a payroll program.Thenext minurte, itcan prepare bills frominvoices under control of a billing

prOgram. Later, this same collectionof components,controlled by yet

another program, can read

statistical data and produce a barchart,or sense the movements of ajoystick and manipulate the positionof an imaginary spaceship on a

display screen

The physical components of a computer—the processor, memory,input devices,and output devices-are its hardware.You can see them, touch them, and feelthem. Programs and data are different,existing only as electronic pulses

stored in memory.Software is ageneral term for programs.

1.4 A Plan of Attack

At this point, you should have a basicsense of the functions of the processor,main memory,input devices,output

devices, and secondary storage, andshould know that a computer processesdata into information under the control ofa program.

over the next several chapters,well discuss each major

component in more detail,beginning with the computeritself.Once we've covered thecomponents, weconsider howthey are assembled to form

complete computer systems. Tohelp you check your

understanding,each chapterends with a brief self-test.

As you study the processor,or memory,or input devices, or software, dont losesight of the fact that a computer is acollection of components,each of whichmust do its part. The basic purpose ofthis first chapter was to give you a high-level overview of a complete computer system.

As you read the next several

chapters, you willencounter a greatdeal of technical detail, and it's easyto "miss the forest for trees." As youread, use the material in this chapteras a framework.