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.