C++ Aptitude With Ans and Explanation

7/27/2019 C++ Aptitude With Ans and Explanation

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BALA KRISHNA.A KRISHNA ACADEMY

C++ Aptitude and OOPSC++ Aptitude and OOPS

1) class Sample

{public: int *ptr; Sample(int i) { ptr = new int(i); } ~Sample() { delete ptr; }

void PrintVal() { cout !"#e value is ! *ptr; }};void Some$unc(Sample %){cout !Sa& i am in some$unc ! endl;}int main(){Sample s1= 1';Some$unc(s1);s1PrintVal();}

Answer:Sa& i am in some$uncull pointer assinment(+un,time error)

Explanation:-s t#e ob.ect is passed b& value to Some$unc t#e destructor o/ t#e

ob.ect is called w#en t#e control returns /rom t#e /unction So w#enPrintVal is called it meets up wit# ptr t#at #as been /reed"#e solution isto pass t#e Sample ob.ect b&referenceto Some$unc:

void Some$unc(Sample 0%){cout !Sa& i am in some$unc ! endl;}

because when we pass objects by refernece that object is notdestroyed. while returning from the function.

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) @#ic# is t#e parameter t#at is added to ever& non,static member/unction w#en it is calledA

Answer: Bt#isC pointer

D) class base

{ public: int bval; base(){ bval=';} };

class deri:public base { public: int dval; deri(){ dval=1;} };void Some$unc(base *arr3int si5e){/or(int i='; isi5e; iEE3arrEE) coutarr,Fbval;coutendl;}

int main(){

base Gase-rrHIJ;Some$unc(Gase-rr3I);deri Keri-rrHIJ;Some$unc(Keri-rr3I);}

Answer:''''''1'1'

Explanation:"#e /unction Some$unc e%pects two aruments"#e /irst one is a

pointer to an arra& o/ base class ob.ects and t#e second one is t#e si5eo/t#e arra&"#e /irst call o/ some$unc calls it wit# an arra& o/ bae ob.ects3 soit worLs correctl& and prints t#e bval o/ all t#e ob.ects @#en Some/unc iscalled t#e second time t#e arument passed is t#e pointeer to an arra& o/derived class ob.ects and not t#e arra& o/ base class ob.ects Gut t#at isw#at t#e /unction e%pects to be sent So t#e derived class pointer ispromoted to base class pointer and t#e address is sent to t#e /unctionSome$unc() Lnows not#in about t#is and .ust treats t#e pointer as anarra& o/ base class ob.ects So w#en arrEE is met3 t#e si5e o/ base classob.ect is taLen into consideration and is incremented b& si5eo/(int) b&tes

/or bval (t#e deri class ob.ects #ave bval and dval as members and so is o/si5e F= si5eo/(int)Esi5eo/(int) )


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2) class base { public: void base$un(){ cout!/rom base!endl;} };

class deri:public base { public: void base$un(){ cout !/rom derived!endl;} };void Some$unc(base *baseMb.){ baseMb.,Fbase$un();}int main(){base baseMb.ect;Some$unc(0baseMb.ect);deri deriMb.ect;Some$unc(0deriMb.ect);}

Answer:/rom base/rom base

Explanation:-s we #ave seen in t#e previous case3 Some$unc e%pects a pointer

to a base class Since a pointer to a derived class ob.ect is passed3 ittreats t#e arument onl& as a base class pointer and t#e correspondinbase /unction is called

I) class base { public: virtual void base$un(){ cout!/rom base!endl;} };class deri:public base {

public: void base$un(){ cout !/rom derived!endl;} };

void Some$unc(base *baseMb.){ baseMb.,Fbase$un();}


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int main(){base baseMb.ect;Some$unc(0baseMb.ect);

deri deriMb.ect;Some$unc(0deriMb.ect);}

Answer:/rom base/rom derived

Explanation:+emember t#at base$unc is a virtual /unction "#at means t#at it

supports run,time pol&morp#ism So t#e /unction correspondin to t#ederived class ob.ect is called

void main(){

int a3 *pa3 0ra;pa = 0a;ra = a;cout !a=!a !*pa=!*pa !ra!ra ;

}N*-nswer :

6ompiler >rror: OraO3re/erence must be initiali5ed>%planation :

Pointers are di//erent /rom re/erences Mne o/ t#e maindi//erences is t#at t#e pointers can be bot# initiali5ed and assined3w#ereas re/erences can onl& be initiali5ed So t#is code issues an error*Nconst int si5e = I;void print(int *ptr){

coutptrH'J;}

void print(int ptrHsi5eJ){

coutptrH'J;}void main(){

int aHsi5eJ = {133D323I};int *b = new int(si5e);print(a);print(b);

}N*


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-nswer:6ompiler >rror : /unction Ovoid print(int *)O alread& #as a bod&

>%planation:-rra&s cannot be passed to /unctions3 onl& pointers (/or arra&s3 base

addresses)can be passed So t#e aruments int *ptr and int prtHsi5eJ #ave nodi//erenceas /unction aruments n ot#er words3 bot# t#e /unctoins #ave t#e samesinature andso cannot be overloaded*N

class some{public:

~some(){

cout!someOs destructor!endl;}

};

void main(){

some s;s~some();

}

N*-nswer:

someOs destructorsomeOs destructor

>%planation:Kestructors can be called e%plicitl& 9ere Os~some()O e%plicitl& calls

t#edestructor o/ OsO @#en main() returns3 destructor o/ s is called aain3#ence t#e result*N

include iostream#F

class /id{

int dim1;int dim;

public:/id() { dim1=I; dim=


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void /id::operator(ostream 0r#s){

r#s t#is,Fdim1! !t#is,Fdim! !;}

N*class /iDd : public /id{

int dimD;public:

/iDd() { dimD=Q;}virtual void operator(ostream 0r#s);

};void /iDd::operator(ostream 0r#s){

/id::operator (r#s);r#st#is,FdimD;

}*N

void main(){

/id ob.1;NN /iDd ob.;

ob.1 cout;NN ob. cout;}N*-nswer :

I %planation:

n t#is proram3 t#e operator is overloaded wit# ostream asarument

"#is enables t#e OcoutO to be present at t#e ri#t,#and,side ormall&3

OcoutOis implemented as lobal /unction3 but it doesnOt mean t#at OcoutO is notpossibleto be overloaded as member /unction Mverloadin as virtual member /unction becomes #and& w#en t#eclass in w#ic#it is overloaded is in#erited3 and t#is becomes available to be overrided

"#is is as opposedto lobal /riend /unctions3 w#ere /riendOs are not in#erited*N


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class opMverload{

public:bool operator==(opMverload temp);

};

bool opMverload::operator==(opMverload temp){i/(*t#is == temp ){

cout!"#e bot# are same ob.ectsRn!;return true;

}else{

cout!"#e bot# are di//erentRn!;return /alse;

}}void main(){

opMverload a13 a;a1= =a;

}

-nswer :+untime >rror: StacL Mver/low

>%planation :8ust liLe normal /unctions3 operator /unctions can be called

recursivel& "#is proram .ust illustrates t#at point3 b& callin t#e operator== /unction recursivel&3 leadin to an in/inite loop

class comple%{double re;double im;

public:comple%() : re(1)3im('I) {}bool operator==(comple% 0r#s);

operator int(){}};

bool comple%::operator == (comple% 0r#s){i/((t#is,Fre == r#sre) 00 (t#is,Fim == r#sim))

return true;else

return /alse;}

int main(){comple% c1;


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cout c1;}-nswer : arbae value

>%planation:

"#e prorammer wis#es to print t#e comple% ob.ect usin outputre,direction operator3w#ic# #e #as not de/ined /or #is lassGut t#ecompiler instead o/ ivin an error sees t#e conversion /unctionand converts t#e user de/ined ob.ect to standard ob.ect and printssome arbae value

class comple%{double re;double im;

public:comple%() : re(')3im(') {}comple%(double n) { re=n3im=n;};comple%(int m3int n) { re=m3im=n;}void print() { coutre; coutim;}

};

void main(){comple% cD;double i=I;cD = i;

cDprint();}

-nswer:I3I

>%planation:"#ou# no operator= /unction taLin comple%3 double is de/ined3

t#e double on t#e r#s is converted into a temporar& ob.ect usin t#esinle arument constructor taLin double and assined to t#e lvalue

void main()

{int a3 *pa3 0ra;pa = 0a;ra = a;cout !a=!a !*pa=!*pa !ra!ra ;

}

-nswer : 6ompiler >rror: OraO3re/erence must be initiali5ed>%planation :

Pointers are di//erent /rom re/erences Mne o/ t#e main

di//erences is t#at t#e pointers can be bot# initiali5ed and assined3w#ereas re/erences can onl& be initiali5ed So t#is code issues an error


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1) Ketermine t#e output o/ t#e O6EEO 6odelet

class base{public :

out(){

cout!base !;}

};class deri{public : out(){cout!deri !;}};void main(){ deri dpHDJ;

base *bp = (base*)dp;/or (int i='; iD;iEE)(bpEE),Fout();

}

) 8usti/& t#e use o/ virtual constructors and destructors in 6EE

D) >ac# 6EE ob.ect possesses t#e 2 member /ns3(w#ic# can be declaredb& t#e prorammer e%plicitl& or b& t#e implementation i/ t#e& are notavailable) @#at are t#ose 2 /unctionsA

2) @#at is wron wit# t#is class declarationAclass somet#in{

c#ar *str;public:

somet#in(){ st = new c#arH1'J; } ~somet#in() {

delete str;}

};

I) n#eritance is also Lnown as ,,,,,,,, relations#ip 6ontainers#ip asTTTTTTTT relations#ip


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1. What is a modifier?Answer: - modi/ier3 also called a modi/&in /unction is a member /unctiont#at c#anes t#e value o/ at least one data member n ot#er words3 anoperation t#at modi/ies t#e state o/ an ob.ect 4odi/iers are also Lnown as

BmutatorsC

2. What is an accessor?Answer: -n accessor is a class operation t#at does not modi/& t#e state o/an ob.ect "#e accessor /unctions need to be declared as constoperations

3. Differentiate between a template class and class template.Answer:Template class:

- eneric de/inition or a parameteri5ed class not instantiated untilt#e client provides t#e needed in/ormation tCs .aron /or plain templatesClass template:

- class template speci/ies #ow individual classes can be constructedmuc# liLe t#e wa& a class speci/ies #ow individual ob.ects can beconstructed tCs .aron /or plain classes

4. When does a name clash occur?Answer: - name clas# occurs w#en a name is de/ined in more t#an oneplace $or e%ample3 two di//erent class libraries could ive two di//erent

classes t#e same name / &ou tr& to use man& class libraries at t#e sametime3 t#ere is a /air c#ance t#at &ou will be unable to compile or linL t#eproram because o/ name clas#es

5. Define namespace.Answer:

t is a /eature in cEE to minimi5e name collisions in t#e lobal namespace "#is namespace Le&word assins a distinct name to a librar& t#atallows ot#er libraries to use t#e same identi/ier names wit#out creatinan& name collisions $urt#ermore3 t#e compiler uses t#e namespacesinature /or di//erentiatin t#e de/initions

6. What is the use of using declaration.Answer:

- usin declaration maLes it possible to use a name /rom anamespace wit#out t#e scope operator

!. What is an "terator class?Answer:

- class t#at is used to traverse t#rou# t#e ob.ects maintained b& acontainer class "#ere are /ive cateories o/ iterators:

input iterators3

output iterators3


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/orward iterators3

bidirectional iterators3

random access-n iterator is an entit& t#at ives access to t#e contents o/ a

container ob.ect wit#out violatin encapsulation constraints -ccess to t#econtents is ranted on a one,at,a,time basis in order "#e order can bestorae order (as in lists and Uueues) or some arbitrar& order (as in arra&indices) or accordin to some orderin relation (as in an ordered binar&tree) "#e iterator is a construct3 w#ic# provides an inter/ace t#at3 w#encalled3 &ields eit#er t#e ne%t element in t#e container3 or some valuedenotin t#e /act t#at t#ere are no more elements to e%amine terators#ide t#e details o/ access to and update o/ t#e elements o/ a containerclass

"#e simplest and sa/est iterators are t#ose t#at permit read,onl&access to t#e contents o/ a container class "#e /ollowin code /rament

s#ows #ow an iterator mi#t appear in code: contTiter:=new contTiterator(); %:=contTiterne%t(); w#ile %N=none do s(%); %:=contTiterne%t(); end; n t#is e%ample3 contTiter is t#e name o/ t#e iterator t is created ont#e /irst line b& instantiation o/ contTiterator class3 an iterator class

de/ined to iterate over some container class3 cont Succesive elements/rom t#e container are carried to % "#e loop terminates w#en % is boundto some empt& value (9ere3 none)n t#e middle o/ t#e loop3 t#ere is s(%)an operation on %3 t#e current element /rom t#e container "#e ne%telement o/ t#e container is obtained at t#e bottom o/ t#e loop

#. $ist out some of the %%D&'( a)ailable.Answer:

>4S"M>NMP-7 o/ emstone s&stems

M"MS o/ Mntos

Mb.ectivit& o/ Mb.ectivit& inc Versant o/ Versant ob.ect tec#nolo&

Mb.ect store o/ Mb.ect Kesin

-+K>" o/ -+K>" so/tware

PM>" o/ PM>" so/tware

1*. $ist out some of the ob+ect,oriented methodologies.Answer:

Mb.ect Mriented Kevelopment (MMK) (Gooc# 11312)

Mb.ect Mriented -nal&sis and Kesin (MM-NK) (6oad and ourdon

11) Mb.ect 4odellin "ec#niUues (M4") (+umbau# 11)


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Mb.ect Mriented So/tware >nineerin (Mb.ector&) (8acobson 1)

Mb.ect Mriented -nal&sis (MM-) (S#laer and 4ellor 1)

"#e $usion 4et#od (6oleman 11)

11. What is an incomplete t-pe?

Answer: ncomplete t&pes re/ers to pointers in w#ic# t#ere is non availabilit&o/ t#e implementation o/ t#e re/erenced location or it points to somelocation w#ose value is not available /or modi/icationExample: int *i='%2'' NN i points to address 2'' *i='; NNset t#e value o/ memor& location pointed b& incomplete t&pes are ot#erwise called uninitiali5ed pointers

12. What is a dangling pointer?

Answer:- danlin pointer arises w#en &ou use t#e address o/ an ob.ecta/ter its li/etime is over

"#is ma& occur in situations liLe returnin addresses o/ t#e automaticvariables /rom a /unction or usin t#e address o/ t#e memor& blocL a/ter itis /reed

13. Differentiate between the message and method.Answer:

Message Method Mb.ects communicate b& sendin

messaes to eac# ot#er

Provides response to a messae

- messae is sent to invoLe amet#od

t is an implementation o/ anoperation

14. What is an adaptor class or Wrapper class?

Answer:- class t#at #as no /unctionalit& o/ its own ts member /unctions

#ide t#e use o/ a t#ird part& so/tware component or an ob.ect wit# t#enon,compatible inter/ace or a non, ob.ect, oriented implementation

15. What is a ull ob+ect?Answer:

t is an ob.ect o/ some class w#ose purpose is to indicate t#at a realob.ect o/ t#at class does not e%ist Mne common use /or a null ob.ect is areturn value /rom a member /unction t#at is supposed to return an ob.ectwit# some speci/ied properties but cannot /ind suc# an ob.ect

16. What is class in)ariant?Answer:

- class invariant is a condition t#at de/ines all valid states /or an

ob.ect t is a loical condition to ensure t#e correct worLin o/ a class6lass invariants must #old w#en an ob.ect is created3 and t#e& must be


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preserved under all operations o/ t#e class n particular all classinvariants are bot# preconditions and post,conditions /or all operations ormember /unctions o/ t#e class

1!. What do -ou mean b- (tac/ unwinding?

Answer:t is a process durin e%ception #andlin w#en t#e destructor is

called /or all local ob.ects between t#e place w#ere t#e e%ception wast#rown and w#ere it is cau#t10. Define precondition and post,condition to a member function.

Answer:Precondition: - precondition is a condition t#at must be true on entr& to amember /unction - class is used correctl& i/ preconditions are never /alse-n operation is not responsible /or doin an&t#in sensible i/ itsprecondition /ails to #old

$or e%ample3 t#e inter/ace invariants o/ stac/ class sa& not#inabout pus#in &et anot#er element on a stacL t#at is alread& /ull @e sa&t#at isfulis a precondition o/ t#epushoperation

Post-condition: - post,condition is a condition t#at must be true on e%it /rom amember /unction i/ t#e precondition was valid on entr& to t#at /unction -class is implemented correctl& i/ post,conditions are never /alse

$or e%ample3 a/ter pus#in an element on t#e stacL3 we Lnow t#at

isempt- must necessaril& #old "#is is a post,condition o/ t#e pushoperation

1! "hat are the conditions that ha#e to $e met %or a conditionto $e an in#ariant o% the class&

Answer:

"#e condition s#ould #old at t#e end o/ ever& constructor

"#e condition s#ould #old at t#e end o/ ever& mutator(non,const)operation

'(! "hat are prox) o$*ects&

Answer:Mb.ects t#at stand /or ot#er ob.ects are called pro%& ob.ects or

surroatesExample: templateclass "F class -rra&K

{ public: class -rra&1K {

public: "0 operatorHJ (int inde%);


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const "0 operatorHJ (int inde%) const; }; -rra&1K operatorHJ (int inde%); const -rra&1K operatorHJ (int inde%) const;

};

"#e /ollowin t#en becomes leal: -rra&K/loatFdata(1'3'); coutdataHDJH


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24. What is an orthogonal base class?

Answer:/ two base classes #ave no overlappin met#ods or data t#e& are

said to be independent o/3 or ort#oonal to eac# ot#er Mrt#oonal in t#esense means t#at two classes operate in di//erent dimensions and do notinter/ere wit# eac# ot#er in an& wa& "#e same derived class ma& in#eritsuc# classes wit# no di//icult&

25. What is a container class? What are the t-pes of container classes?Answer:

- container class is a class t#at is used to #old ob.ects in memor& ore%ternal storae - container class acts as a eneric #older - containerclass #as a prede/ined be#avior and a well,Lnown inter/ace - containerclass is a supportin class w#ose purpose is to #ide t#e topolo& used /ormaintainin t#e list o/ ob.ects in memor& @#en a container class containsa roup o/ mi%ed ob.ects3 t#e container is called a #eteroeneouscontainer; w#en t#e container is #oldin a roup o/ ob.ects t#at are all t#esame3 t#e container is called a #omoeneous container

26. What is a protocol class?Answer:

-n abstract class is a protocol class i/:

it neit#er contains nor in#erits /rom classes t#at contain memberdata3 non,virtual /unctions3 or private (or protected) members o/ an&Lind

it #as a non,inline virtual destructor de/ined wit# an empt&implementation3

all member /unctions ot#er t#an t#e destructor includin in#erited/unctions3 are declared pure virtual /unctions and le/t unde/ined

2!. What is a miin class?Answer:

- class t#at provides some but not all o/ t#e implementation /or avirtual base class is o/ten called mi%in Kerivation done .ust /or t#epurpose o/ rede/inin t#e virtual /unctions in t#e base classes is o/tencalled mi%in in#eritance 4i%in classes t&picall& donOt s#are commonbases

20. What is a concrete class?Answer:

- concrete class is used to de/ine a use/ul ob.ect t#at can beinstantiated as an automatic variable on t#e proram stacL "#eimplementation o/ a concrete class is de/ined "#e concrete class is not

intended to be a base class and no attempt to minimi5e dependenc& onot#er classes in t#e implementation or be#avior o/ t#e class


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2#.What is the handle class?Answer:- #andle is a class t#at maintains a pointer to an ob.ect t#at isprorammaticall& accessible t#rou# t#e public inter/ace o/ t#e #andleclass

Explanation:n case o/ abstract classes3 unless one manipulates t#e ob.ects o/

t#ese classes t#rou# pointers and re/erences3 t#e bene/its o/ t#e virtual/unctions are lost Wser code ma& become dependent on details o/implementation classes because an abstract t&pe cannot be allocatedstatisticall& or on t#e stacL wit#out its si5e bein Lnown Wsin pointers orre/erences implies t#at t#e burden o/ memor& manaement /alls on t#euser -not#er limitation o/ abstract class ob.ect is o/ /i%ed si5e 6lasses#owever are used to represent concepts t#at reUuire var&in amounts o/storae to implement t#em- popular tec#niUue /or dealin wit# t#ese issues is to separate w#at isused as a sinle ob.ect in two parts: a #andle providin t#e user inter/aceand a representation #oldin all or most o/ t#e ob.ectOs state "#econnection between t#e #andle and t#e representation is t&picall& apointer in t#e #andle M/ten3 #andles #ave a bit more data t#an t#e simplerepresentation pointer3 but not muc# more 9ence t#e la&out o/ t#e#andle is t&picall& stable3 even w#en t#e representation c#anes and alsot#at #andles are small enou# to move around relativel& /reel& so t#at t#euser neednCt use t#e pointers and t#e re/erences

3*. What is an action class?

Answer:"#e simplest and most obvious wa& to speci/& an action in 6EE is to

write a /unction 9owever3 i/ t#e action #as to be dela&ed3 #as to betransmitted Oelsew#ereO be/ore bein per/ormed3 reUuires its own data3#as to be combined wit# ot#er actions3 etc t#en it o/ten becomesattractive to provide t#e action in t#e /orm o/ a class t#at can e%ecute t#edesired action and provide ot#er services as well 4anipulators used wit#iostreams is an obvious e%ampleExplanation:

A common form of action class is a simple class containingjust one virtual function.

class -ction { public: virtual int doTit( int )='; virtual ~-ction( ); }

Given this we can write code say a member that can storeactions for later e!ecution without using pointers to functionswithout "nowing anything about the objects involved andwithout even "nowing the name of the operation it invo"es. #ore!ample$

class writeT/ile : public -ction { $ile0 /;


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public: int doTit(int) { return /write( )suceed( ); }

}; class errorTmessae: public -ction { responseTbo% db(messaecstr( )3!6ontinue!3!6ancel!3!+etr&!); switc# (dbetresponse( )) { case ': return '; case 1: abort(); case : currentToperationredo( );return 1; } };

- user o/ t#e -ction class will be completel& isolated /rom an&Lnowlede o/ derived classes suc# as writeT/ile and errorTmessae

31. When can -ou tell that a memor- lea/ will occur?Answer:

- memor& leaL occurs w#en a proram loses t#e abilit& to /ree ablocL o/ d&namicall& allocated memor&

32.What is a parameteried t-pe?

Answer:- template is a parameteri5ed construct or t&pe containin eneric

code t#at can use or manipulate an& t&pe t is called parameteri5edbecause an actual t&pe is a parameter o/ t#e code bod& Pol&morp#ismma& be ac#ieved t#rou# parameteri5ed t&pes "#is t&pe o/ pol&morp#ismis called parameteric pol&morp#ism Parameteric pol&morp#ism is t#emec#anism b& w#ic# t#e same code is used on di//erent t&pes passed asparameters

33. Differentiate between a deep cop- and a shallow cop-?

Answer:Keep cop& involves usin t#e contents o/ one ob.ect to createanot#er instance o/ t#e same class n a deep cop&3 t#e two ob.ects ma&contain #t same in/ormation but t#e taret ob.ect will #ave its own bu//ersand resources t#e destruction o/ eit#er ob.ect will not a//ect t#eremainin ob.ect "#e overloaded assinment operator would create adeep cop& o/ ob.ects

S#allow cop& involves cop&in t#e contents o/ one ob.ect intoanot#er instance o/ t#e same class t#us creatin a mirror imae Mwin tostrai#t cop&in o/ re/erences and pointers3 t#e two ob.ects will s#are t#esame e%ternall& contained contents o/ t#e ot#er ob.ect to be

unpredictableExplanation:


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Wsin a cop& constructor we simpl& cop& t#e data values memberb& member "#is met#od o/ cop&in is called s#allow cop& / t#e ob.ect isa simple class3 comprised o/ built in t&pes and no pointers t#is would beacceptable "#is /unction would use t#e values and t#e ob.ects and itsbe#avior would not be altered wit# a s#allow cop&3 onl& t#e addresses o/

pointers t#at are members are copied and not t#e value t#e address ispointin to "#e data values o/ t#e ob.ect would t#en be inadvertentl&altered b& t#e /unction @#en t#e /unction oes out o/ scope3 t#e cop& o/t#e ob.ect wit# all its data is popped o// t#e stacL

/ t#e ob.ect #as an& pointers a deep cop& needs to be e%ecuted@it# t#e deep cop& o/ an ob.ect3 memor& is allocated /or t#e ob.ect in /reestore and t#e elements pointed to are copied - deep cop& is used /orob.ects t#at are returned /rom a /unction

34. What is an opaue pointer?Answer:

- pointer is said to be opaUue i/ t#e de/inition o/ t#e t&pe to w#ic# itpoints to is not included in t#e current translation unit - translation unit ist#e result o/ merin an implementation /ile wit# all its #eaders and#eader /iles

35. What is a smart pointer?Answer:

- smart pointer is an ob.ect t#at acts3 looLs and /eels liLe a normalpointer but o//ers more /unctionalit& n 6EE3 smart pointers areimplemented as template classes t#at encapsulate a pointer and override

standard pointer operators "#e& #ave a number o/ advantaes overreular pointers "#e& are uaranteed to be initiali5ed as eit#er nullpointers or pointers to a #eap ob.ect ndirection t#rou# a null pointer isc#ecLed o delete is ever necessar& Mb.ects are automaticall& /reedw#en t#e last pointer to t#em #as one awa& Mne sini/icant problemwit# t#ese smart pointers is t#at unliLe reular pointers3 t#e& donOtrespect in#eritance Smart pointers are unattractive /or pol&morp#ic codeiven below is an e%ample /or t#e implementation o/ smart pointersExample:

template class XF class smartTpointer

{ public: smartTpointer(); NN maLes a null pointer smartTpointer(const X0 %) NN maLes pointer to cop& o/ %

X0 operator *( ); const X0 operator*( ) const; X* operator,F() const;

smartTpointer(const smartTpointer XF 0);

const smartTpointer XF 0 operator =(constsmartTpointerXF0);


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~smartTpointer(); private: NN };

"#is class implement a smart pointer to an ob.ect o/ t&pe X "#e

ob.ect itsel/ is located on t#e #eap 9ere is #ow to use it: smartTpointer emplo&eeF p= emplo&ee(!9arris!31DDD);7iLe ot#er overloaded operators3 p will be#ave liLe a reular pointer3cout*p;p,FraiseTsalar&('I);

36. What is reflei)e association?Answer:

"#e Ois,aO is called a re/le%ive association because t#e re/le%iveassociation permits classes to bear t#e is,a association not onl& wit# t#eirsuper,classes but also wit# t#emselves t di//ers /rom a Ospeciali5es,/romOas Ospeciali5es,/romO is usuall& used to describe t#e association between asuper,class and a sub,class $or e%ample:

Printer is,a printer

3!. What is slicing?Answer:

Slicin means t#at t#e data added b& a subclass are discarded w#enan ob.ect o/ t#e subclass is passed or returned b& value or /rom a /unctione%pectin a base class ob.ectExplanation:

6onsider t#e /ollowin class declaration: class base { base0 operator =(const base0); base (const base0); } void /un( ) { base e=m; e=m;

}-s base cop& /unctions donOt Lnow an&t#in about t#e derived onl&

t#e base part o/ t#e derived is copied "#is is commonl& re/erred to asslicin Mne reason to pass ob.ects o/ classes in a #ierarc#& is to avoidslicin Mt#er reasons are to preserve pol&morp#ic be#avior and to aine//icienc&

30. What is name mangling?Answer:

ame manlin is t#e process t#rou# w#ic# &our cEE compilers ive

eac# /unction in &our proram a uniUue name n 6EE3 all prorams#ave at,least a /ew /unctions wit# t#e same name ame manlin is a


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concession to t#e /act t#at linLer alwa&s insists on all /unction namesbein uniUue

Example:n eneral3 member names are made uniUue b& concatenatin t#e

name o/ t#e member wit# t#at o/ t#e class e iven t#e declaration: class Gar { public:

int ival; };

ival becomes somet#in liLe: NN a possible member name manlin ivalTTDGar6onsider t#is derivation: class $oo : public Gar

{public:

int ival; }

"#e internal representation o/ a $oo ob.ect is t#e concatenation o/ itsbase and derived class members

NN Pseudo 6EE code NN nternal representation o/ $oo class $oo { public:

int ivalTTDGar; int ivalTTD$oo; };

Wnambiuous access o/ eit#er ival members is ac#ieved t#rou# namemanlin 4ember /unctions3 because t#e& can be overloaded3 reUuirean e%tensive manlin to provide eac# wit# a uniUue name 9ere t#ecompiler enerates t#e same name /or t#e two overloadedinstances("#eir arument lists maLe t#eir instances uniUue)

3#. What are pro- ob+ects?Answer:


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Mb.ects t#at points to ot#er ob.ects are called pro%& ob.ects orsurroates ts an ob.ect t#at provides t#e same inter/ace as its serverob.ect but does not #ave an& /unctionalit& Kurin a met#od invocation3 itroutes data to t#e true server ob.ect and sends bacL t#e return value tot#e ob.ect

4*. Differentiate between declaration and definition in 77.Answer:

- declaration introduces a name into t#e proram; a de/inition providesa uniUue description o/ an entit& (e t&pe3 instance3 and /unction)Keclarations can be repeated in a iven scope3 it introduces a name ina iven scope "#ere must be e%actl& one de/inition o/ ever& ob.ect3/unction or class used in a 6EE proram

- declaration is a de/inition unless:

it declares a /unction wit#out speci/&in its bod&3

it contains an e%tern speci/ier and no initiali5er or /unction bod&3

it is t#e declaration o/ a static class data member wit#out a classde/inition3

it is a class name de/inition3

it is a t&pede/ declarationA definition is a declaration unless$

it de/ines a static class data member3

it de/ines a non,inline member /unction41. What is cloning?

Answer: -n ob.ect can carr& out cop&in in two wa&s ie it can set itsel/to be a cop& o/ anot#er ob.ect3 or it can return a cop& o/ itsel/ "#e latter

process is called clonin

42. Describe the main characteristics of static functions.Answer:

"#e main c#aracteristics o/ static /unctions include3

t is wit#out t#e a t#is pointer3

t canOt directl& access t#e non,static members o/ its class

t canOt be declared const3 volatile or virtual

t doesnOt need to be invoLed t#rou# an ob.ect o/ its class3alt#ou# /or convenience3 it ma&

43. Will the inline function be compiled as the inline function alwa-s?8ustif-.Answer:

-n inline /unction is a reUuest and not a command 9ence it wonOtbe compiled as an inline /unction alwa&sExplanation:

nline,e%pansion could /ail i/ t#e inline /unction contains loops3 t#eaddress o/ an inline /unction is used3 or an inline /unction is called in acomple% e%pression "#e rules /or inlinin are compiler dependent

44. Define a wa- other than using the /e-word inline to ma/e a functioninline.


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Answer:"#e /unction must be de/ined inside t#e class

45. 9ow can a :;;: operator be used as unar- operator?Answer:

"#e scope operator can be used to re/er to members o/ t#e lobalnamespace Gecause t#e lobal namespace doesnCt #ave a name3 t#enotation :: member,name re/ers to a member o/ t#e lobal namespace

"#is can be use/ul /or re/errin to members o/ lobal namespace w#osenames #ave been #idden b& names declared in nested local scope Wnlesswe speci/& to t#e compiler in w#ic# namespace to searc# /or adeclaration3 t#e compiler simple searc#es t#e current scope3 and an&scopes in w#ic# t#e current scope is nested3 to /ind t#e declaration /or t#ename

46. What is placement new?Answer:

%hen you want to call a constructor directly you use theplacement new. Sometimes you have some raw memory that&salready been allocated and you need to construct an object inthe memory you have. Operator new&s special version placementnew allows you to do it. class @idet { public : @idet(int widetsi5e);

@idet* 6onstructTwidetTintTbu//er(void *bu//er3intwidetsi5e) { return new(bu//er) @idet(widetsi5e); } };

'his function returns a pointer to a %idget object that&sconstructed within the buffer passed to the function. Such afunction might be useful for applications using shared memory ormemory(mapped )*O because objects in such applications must

be placed at specific addresses or in memory allocated by specialroutines.


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BALA KRISHNA.A KRISHNA ACADEMY24

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C++ Aptitude With Ans and Explanation