C++常见英文面试笔精彩试题Word格式文档下载.docx
《C++常见英文面试笔精彩试题Word格式文档下载.docx》由会员分享，可在线阅读，更多相关《C++常见英文面试笔精彩试题Word格式文档下载.docx（20页珍藏版）》请在冰点文库上搜索。
Whatiscopyconstructor?
Constructorwhichinitializestheit'
sobjectmembervariables（byshallowcopying）withanotherobjectofthesameclass.Ifyoudon'
timplementoneinyourclassthencompilerimplementsoneforyou.
forexample:
BooObj1（10）;
//callingBooconstructor
BooObj2（Obj1）;
//callingboocopyconstructor
BooObj2=Obj1;
//callingboocopyconstructor
Whenarecopyconstructorscalled?
Copyconstructorsarecalledinfollowingcases:
a）whenafunctionreturnsanobjectofthatclassbyvalue
b）whentheobjectofthatclassispassedbyvalueasanargumenttoafunction
c）whenyouconstructanobjectbasedonanotherobjectofthesameclass
d）Whencompilergeneratesatemporaryobject
Whatisassignmentoperator?
Defaultassignmentoperatorhandlesassigningoneobjecttoanotherofthesameclass.Membertomembercopy（shallowcopy）
Whatarealltheimplicitmemberfunctionsoftheclass?
Orwhatareallthefunctionswhichcompilerimplementsforusifwedon'
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?
Thereisnowayforthecompilertoverifythatthemacroparametersareofcompatibletypes.Themacroisexpandedwithoutanyspecialtypechecking.
Ifmacroparameterhasapost-incrementedvariable（likec++）,theincrementisperformedtwotimes.
Becausemacrosareexpandedbythepreprocessor,compilererrormessageswillrefertotheexpandedmacro,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.asuggestiontothecompilertouseaCPUregisterforperformance
static:
avariablethatisknownonlyinthefunctionthatcontainsitsdefinitionbutisneverdestroyedandretains=keepitsvaluebetweencallstothatfunction.Itexistsfromthetimetheprogrambeginsexecution
extern:
astaticvariablewhosedefinitionandplacementisdeterminedwhenallobjectandlibrarymodulesarecombined（linked）toformtheexecutablecodefile.Itcanbevisibleoutsidethefilewhereitisdefined.
WhatarestoragequalifiersinC++?
Theyare..
const
volatile
mutable
Constkeywordindicatesthatmemoryonceinitialized,shouldnotbealteredbyaprogram.
volatilekeywordindicatesthatthevalueinthememorylocationcanbealteredeventhoughnothingintheprogram
codemodifiesthecontents.forexampleifyouhaveapointertohardwarelocationthatcontainsthetime,wherehardwarechangesthevalueofthispointervariableandnottheprogram.Theintentofthiskeywordtoimprovetheoptimizationabilityofthecompiler.
mutablekeywordindicatesthatparticularmemberofastructureorclasscanbealteredevenifaparticularstructurevariable,class,orclassmemberfunctionisconstant.
structdata
charname[80];
mutabledoublesalary;
constdataMyStruct={"
SatishShetty"
1000};
//initlizedbycomplier
strcpy（MyStruct.name,"
ShilpaShetty"
）;
//compilererror
MyStruct.salaray=2000;
//complierishappyallowed
Whatisreference?
referenceisanamethatactsasanalias,oralternativename,forapreviouslydefinedvariableoranobject.
prependingvariablewith"
&
symbolmakesitasreference.
inta;
int&
b=a;
读amp
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）Usingconstprotectsyouagainstprogrammingerrorsthatinadvertently不经意的alterdata.
b）Usingconstallowsfunctiontoprocessbothconstandnon-constactualarguments,whileafunctionwithoutconstintheprototypecanonlyacceptnonconstantarguments.
c）Usingaconstreferenceallowsthefunctiontogenerateanduseatemporaryvariableappropriately.
WhenaretemporaryvariablescreatedbyC++compiler?
Providedthatfunctionparameterisa"
constreference"
compilergeneratestemporaryvariableinfollowing2ways.
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?
Whenyoudefineonlyfunctionprototypeinabaseclasswithoutimplementationanddothecompleteimplementation实现inderivedclass.Thisbaseclassiscalledabstractclassandclientwon'
tabletoinstantiateanobjectusingthisbaseclass.
Youcanmakeapurevirtualfunctionorabstractclassthisway..
voidfoo（）=0;
BooMyBoo;
//compilationerror
WhatisMemoryalignment?
Thetermalignmentprimarilymeansthetendency趋向ofanaddresspointerva
升级会员 