The CPU processes data by executing commands from memory through its ALU and control unit in machine cycles. Main memory temporarily stores data and commands being used, while storage holds input/output and working data until processing is complete. An operating system manages the computer's basic functions and allows multiple applications to run by allocating memory and machine cycles.

1. How Computerprocessdata:
• The CPU, or Central ProcessingUnit,is the part of the computerwhere workgetsdone.In
mostcomputers,there isone processingchip
ALU
• ALU stands forArithmetic/LogicUnit
• Thisis the part that executesthe computer'scommands.
A commandmustbe eitherabasicarithmetic operation:
+ - * /
or one of the logical comparisons: >< =not=
• Everythinghasto be brokendownintothese few operations.
• The ALU can onlydo one thingat a time but can workveryfast.
Main Memory
• Main Memorystoresthe commandsthat the CPU executesandthe results.
• Thisis where the computerstoresthe dataand commandsthat are currentlybeingused.
• Whenthe computeristurnedoff,all data inMain Memory vanishes.
• A data storage methodof thistype iscalledvolatile since the data"evaporates."
• The CPU can fetchone piece of data inone machine cycle.

2. Machine cycle
Control Unit
• Thisis the part of the computerthatcontrolsthe Machine Cycle.
• It takesnumerouscyclestodoevena simple additionof twonumbers.
• Fetch- • getan instructionfromMain Memory
• Decode - • translate itintocomputercommands
• Execute - • actuallyprocessthe command
• Store - • write the resulttoMain Memory
OperatingSystem
• Thisis the instructionsthatthe computerusestotell itself how it"operates".It'sthe answer
to "Who am I and whatcan I do?"
• Some commonoperatingsystemsare DOS,variousversionsof Windows,OS/2,UNIX,LINUX,
System7. These all behave inverydifferentwaysandhave differenthardware
requirements.Sotheywon'tall runon all machines
Applications
• These are the variousprogramsthatare currentlyrunningonthe computer.

3. • By takingturnswiththe Machine Cycle,moderncomputers canhave several different
programsrunningat once.Thisis called multi-tasking.
• Each openapplicationhastohave some data storedinMain Memory,evenif the application
ison rest breakandis justsittingthere.
Input / Output Storage
• Whenyouenternewdata, the keystrokesmustbe storeduntil the computercando
somethingwiththe newdata.
• Whenyouwant data printedoutor displayed,itmustbe storedsomewherehandyfirst.
WorkingStorage
• The numbersand charactersthat are the intermediateresultsof computeroperationsmust
be storeduntil the final valuesare calculated.Thesevalues"inprogress"are keptin
temporarylocations.
• For example,if the computerisaddingupthe numbers3, 5, and 6, it wouldfirstadd3 to 5
whichyieldsavalue of 8. The 8 is storedin working storage.Thenthe 8 and 6 are addedand
the newvalue 14 isstored.The value of 14 is now available tobe displayedonthe screenor
to be printedor to be usedinanothercalculation.
UnusedStorage
• One hopesthatthere is alwayssome storage space thatis notin use.
• If space runsout inMain Memory,the computerwill crash,that is,stopworking.
Data representation,and Data processingina computer:
DefinitionofData:
• Data is distinctpiecesof information,usuallyformattedinaspecial way.All software is
dividedintotwo
• general categories:dataandprograms.Programsare collectionsof instructionsfor
manipulatingdata.
• Data can existinavarietyof forms -- as numbersortexton piecesof paper,asbitsand bytes
storedinelectronicmemory,orasfacts storedina person'smind.
• Strictlyspeaking,dataisthe plural of datum, a single piece of information.
• In practice,however,peopleuse dataasboth the singularandplural formof the word.
Basic data type

4. • In programming,classificationof aparticulartype of information.Itiseasyforhumansto
distinguish betweendifferenttypesof data.
• We can usuallytell ata glance whetheranumberisa percentage,atime,oran amountof
money.We do thisthroughspecial symbols -- %,:,and$ -- that indicate the data'stype.
• Similarly,acomputerusesspecial internalcodestokeeptrackof the differenttypesof data
it processes.
Most programminglanguagesrequire the programmertodeclare the datatype of every
data object,andmost
database systemsrequire the usertospecifythe type of eachdatafield.The available data
typesvaryfrom
one programminglanguage toanother,andfromone database applicationtoanother,but
the following
usually
existin one formor another:
• integer:In more commonparlance,whole number;anumberthathas no fractional part.
• floating-point:A numberwitha decimal point.
• For example,3isan integer,but3.5 isa floating-pointnumber.
character (text):Readable text
Storage of data as files
• Computerdatastorage,oftencalledstorage ormemory,isa technologyconsistingof
computercomponentsandrecordingmediausedtoretaindigital data.
• It isa core functionandfundamental componentof computers.
• The central processingunit(CPU) of a computeriswhat manipulatesdata
by performingcomputations.
• A moderndigital computerrepresentsdatausingthe binarynumeral system.
• Text,numbers,pictures,audio,andnearlyanyotherformof informationcanbe converted
intoa stringof bits,or binarydigits,eachof whichhasa value of 1 or 0.
• The most commonunitof storage isthe byte,equal to8 bits.