推荐C++常见英文面试笔试题 精品Word格式文档下载.docx

推荐C++常见英文面试笔试题 精品Word格式文档下载.docx

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Whatiscopyconstructor?

Constructorwhichinitializestheit'

sobjectmembervariables（byshallowcopying）withanotherobjectofthesameclass.Ifyoudon'

timplementoneinyourclassthenpilerimplementsoneforyou.

forexample:

BooObj1（10）;

//callingBooconstructor

BooObj2（Obj1）;

//callingboocopyconstructor

BooObj2=Obj1;

//callingboocopyconstructor

Whenarecopyconstructorscalled?

Copyconstructorsarecalledinfollowingcases:

a）whenafunctionreturnsanobjectofthatclassbyvalue

b）whentheobjectofthatclassispassedbyvalueasanargumenttoafunction

c）whenyouconstructanobjectbasedonanotherobjectofthesameclass

d）Whenpilergeneratesatemporaryobject

Whatisassignmentoperator?

Defaultassignmentoperatorhandlesassigningoneobjecttoanotherofthesameclass.Membertomembercopy（shallowcopy）

Whatarealltheimplicitmemberfunctionsoftheclass?

Orwhatareallthefunctionswhichpilerimplementsforusifwedon'

tdefineone.?

defaultctor

copyctor

assignmentoperator

defaultdestructor

addressoperator

Whatisconversionconstructor?

constructorwithasingleargumentmakesthatconstructorasconversionctoranditcanbeusedfortypeconversion.

classBoo

{

public:

Boo（inti）;

};

BooBooObject=10;

//assigningint10Booobject

Whatisconversionoperator?

classcanhaveapublicmethodforspecificdatatypeconversions.

doublevalue;

Boo（inti）

operatordouble（）

{

returnvalue;

}

BooBooObject;

doublei=BooObject;

//assigningobjecttovariableioftypedouble.nowconversionoperatorgetscalledtoassignthevalue.

Whatisdiffbetweenmalloc（）/free（）andnew/delete?

mallocallocatesmemoryforobjectinheapbutdoesn'

tinvokeobject'

sconstructortoinitiallizetheobject.

newallocatesmemoryandalsoinvokesconstructortoinitializetheobject.

malloc（）andfree（）donotsupportobjectsemantics

Doesnotconstructanddestructobjects

string*ptr=（string*）（malloc（sizeof（string）））

Arenotsafe

Doesnotcalculatethesizeoftheobjectsthatitconstruct

Returnsapointertovoid

int*p=（int*）（malloc（sizeof（int）））;

int*p=newint;

Arenotextensible

newanddeletecanbeoverloadedinaclass

"

delete"

firstcallstheobject'

sterminationroutine（i.e.itsdestructor）andthenreleasesthespacetheobjectoccupiedontheheapmemory.Ifanarrayofobjectswascreatedusingnew,thendeletemustbetoldthatitisdealingwithanarraybyprecedingthenamewithanempty[]:

-

Int_t*my_ints=newInt_t[10];

...

delete[]my_ints;

whatisthediffbetween"

new"

and"

operatornew"

?

workslikemalloc.

Whatisdifferencebetweentemplateandmacro?

Thereisnowayforthepilertoverifythatthemacroparametersareofpatibletypes.Themacroisexpandedwithoutanyspecialtypechecking.

Ifmacroparameterhasapostincrementedvariable（likec++）,theincrementisperformedtwotimes.

Becausemacrosareexpandedbythepreprocessor,pilererrormessageswillrefertotheexpandedmacro,ratherthanthemacrodefinitionitself.Also,themacrowillshowupinexpandedformduringdebugging.

Macro:

#definemin（i,j）（i<

j?

i:

j）

template:

template<

classT>

Tmin（Ti,Tj）

{

returni<

j;

}

WhatareC++storageclasses?

auto

register

static

extern

auto:

thedefault.Variablesareautomaticallycreatedandinitializedwhentheyaredefinedandaredestroyedattheendoftheblockcontainingtheirdefinition.Theyarenotvisibleoutsidethatblock

register:

atypeofautovariable.asuggestiontothepilertouseaCPUregisterforperformance

static:

avariablethatisknownonlyinthefunctionthatcontainsitsdefinitionbutisneverdestroyedandretainsitsvaluebetweencallstothatfunction.Itexistsfromthetimetheprogrambeginsexecution

extern:

astaticvariablewhosedefinitionandplacementisdeterminedwhenallobjectandlibrarymodulesarebined（linked）toformtheexecutablecodefile.Itcanbevisibleoutsidethefilewhereitisdefined.

WhatarestoragequalifiersinC++?

Theyare..

const

volatile

mutable

Constkeywordindicatesthatmemoryonceinitialized,shouldnotbealteredbyaprogram.

volatilekeywordindicatesthatthevalueinthememorylocationcanbealteredeventhoughnothingintheprogram

codemodifiesthecontents.forexampleifyouhaveapointertohardwarelocationthatcontainsthetime,wherehardwarechangesthevalueofthispointervariableandnottheprogram.Theintentofthiskeywordtoimprovetheoptimizationabilityofthepiler.

mutablekeywordindicatesthatparticularmemberofastructureorclasscanbealteredevenifaparticularstructurevariable,class,orclassmemberfunctionisconstant.

structdata

charname[80];

mutabledoublesalary;

constdataMyStruct={"

SatishShetty"

1000};

//initlizedbyplier

strcpy（MyStruct.name,"

ShilpaShetty"

）;

//pilererror

MyStruct.salaray=2000;

//plierishappyallowed

Whatisreference?

referenceisanamethatactsasanalias,oralternativename,forapreviouslydefinedvariableoranobject.

prependingvariablewith"

&

symbolmakesitasreference.

inta;

int&

b=a;

Whatispassingbyreference?

Methodofpassingargumentstoafunctionwhichtakesparameteroftypereference.

voidswap（int&

x,int&

y）

inttemp=x;

x=y;

y=temp;

inta=2,b=3;

swap（a,b）;

Basically,insidethefunctiontherewon'

tbeanycopyofthearguments"

x"

y"

insteadtheyrefertooriginalvariablesaandb.sonoextramemoryneededtopassargumentsanditismoreefficient.

Whendouse"

const"

referenceargumentsinfunction?

a）Usingconstprotectsyouagainstprogrammingerrorsthatinadvertentlyalterdata.

b）Usingconstallowsfunctiontoprocessbothconstandnon-constactualarguments,whileafunctionwithoutconstintheprototypecanonlyacceptnonconstantarguments.

c）Usingaconstreferenceallowsthefunctiontogenerateanduseatemporaryvariableappropriately.

WhenaretemporaryvariablescreatedbyC++piler?

Providedthatfunctionparameterisa"

constreference"

pilergeneratestemporaryvariableinfollowing2ways.

a）Theactualargumentisthecorrecttype,butitisn'

tLvalue

doubleCube（constdouble&

num）

num=num*num*num;

returnnum;

doubletemp=2.0;

doublevalue=cube（3.0+temp）;

//argumentisaexpressionandnotaLvalue;

b）Theactualargumentisofthewrongtype,butofatypethatcanbeconvertedtothecorrecttype

longtemp=3L;

doublevalue=cuberoot（temp）;

//longtodoubleconversion

Whatisvirtualfunction?

Whenderivedclassoverridesthebaseclassmethodbyredefiningthesamefunction,thenifclientwantstoaccessredefinedthemethodfromderivedclassthroughapointerfrombaseclassobject,thenyoumustdefinethisfunctioninbaseclassasvirtualfunction.

classparent

voidShow（）

cout<

<

"

i'

mparent"

<

endl;

classchild:

publicparent

mchild"

parent*parent_object_ptr=newchild;

parent_object_ptr->

show（）//callsparent->

show（）i

nowwegotovirtualworld...

virtualvoidShow（）

show（）//callschild->

show（）

Whatispurevirtualfunction?

orwhatisabstractclass?

Whenyoudefineonlyfunctionprototypeinabaseclasswithoutimplementationanddothepleteimplementationinderivedclass.Thisbaseclassiscalledabstractclassandclientwon'

tabletoinstantiateanobjectusingthisbaseclass.

Youcanmakeapurevirtualfunctionorabstractclassthisway..

voidfoo（）=0;

BooMyBoo;

//pilationerror

WhatisMemoryalignment?

Thetermalignmentprimarilymeansthetendencyofanaddresspointervaluetobeamultipleofsomepoweroftwo.Soapointerwithtwobytealignmenthasazerointheleastsignificantbit.Andapointerwithfourbytealignmenthasazeroinboththetwoleast