C++常见英文面试笔试题.docx

C++常见英文面试笔试题.docx

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C++常见英文面试笔试题

C++-常见英文面试笔试题

C/C++Programminginterviewquestionsandanswers

BySatishShetty,July14th,2004

Whatisencapsulation?

?

Containingandhidinginformationaboutanobject,suchasinternaldatastructuresandcode.Encapsulationisolates（使隔离）theinternalcomplexityofanobject'soperationfromtherestoftheapplication.Forexample,aclientcomponentaskingfornetrevenue（收益）fromabusinessobjectneednotknowthedata'sorigin.

Whatisinheritance?

Inheritanceallowsoneclasstoreusethestateandbehaviorofanotherclass.Thederivedclassinheritsthepropertiesandmethodimplementationsofthebaseclassandextendsitbyoverridingmethodsandaddingadditionalpropertiesandmethods.

WhatisPolymorphism?

?

Polymorphismallowsaclienttotreatdifferent

tomembercopy（shallowcopy）

Whatarealltheimplicitmemberfunctionsoftheclass?

Orwhatareallthefunctionswhichcompilerimplementsforusifwedon'tdefineone.?

?

defaultctor

copyctor

assignmentoperator

defaultdestructor

addressoperator

Whatisconversionconstructor?

constructorwithasingleargumentmakesthatconstructorasconversionctoranditcanbeusedfortypeconversion.

forexample:

classBoo

{

public:

Boo（inti）;

};

BooBooObject=10;//assigningint10Booobject

Whatisconversionoperator?

?

classcanhaveapublicmethodforspecificdatatypeconversions.

forexample:

classBoo

{

doublevalue;

public:

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"?

"operatornew"workslikemalloc.

Whatisdifferencebetweentemplateandmacro?

?

Thereisnowayforthecompilertoverifythatthemacroparametersareofcompatibletypes.Themacroisexpandedwithoutanyspecialtypechecking.

Ifmacroparameterhasapost-incrementedvariable（likec++）,theincrementisperformedtwotimes.

Becausemacrosareexpandedbythepreprocessor,compilererrormessageswillrefertotheexpandedmacro,ratherthanthemacrodefinitionitself.Also,themacrowillshowupinexpandedformduringdebugging.

forexample:

Macro:

#definemin（i,j）（i

i:

j）

template:

template

Tmin（Ti,Tj）

{

returni

i:

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.

struct