Chapter 3: Implementation of OOP Concepts in C++ Class 12 Computer Science NCERT Solutions

Class 12 Computer Science (C++) – Chapter 3: Implementation of OOP Concepts in C++

Short Answer Type Questions

Question 1: Observe the following C++ code and answer the question (i) and (ii): [Delhi, 2015]

class Traveller {
    long PNR;
    char TName[20];
public:
    Traveller() // Function 1
    {
        cout << "Ready" << endl;
    }
    void Book(long P, char N[]) // Function 2
    {
        PNR = P;
        strcpy(TName, N);
    }
    void Print() // Function 3
    {
        cout << PNR << TName << endl;
    }
    ~Traveller() // Function 4
    {
        cout << "Booking cancelled!" << endl;
    }
};

void main() {
    Traveller T;
    T.Book(1234567, "Ravi");     // Line 1
    T.Print();                   // Line 2
}

(i) Function 2 and Function 3 are executed using:
Line 1: T.Book(1234567, "Ravi");
Line 2: T.Print();

(ii) The function executed at the end of } is Function 4: ~Traveller().
It is referred to as a Destructor.

Question 2: Write the definition of a class PIC in C++ with the following description: [Delhi, 2015]

Category & Location Mapping:

• Classic → Amina
• Modern → Jim Plaq
• Antique → Ustad Khan

class PIC {
    int Pno;
    char Category[20];
    char Location[20];

    void FixLocation();

public:
    void Enter();
    void SeeAll();
};

void PIC::FixLocation() {
    if (strcmpi(Category, "Classic") == 0)
        strcpy(Location, "Amina");
    else if (strcmpi(Category, "Modern") == 0)
        strcpy(Location, "Jim Plaq");
    else if (strcmpi(Category, "Antique") == 0)
        strcpy(Location, "Ustad Khan");
}

void PIC::Enter() {
    cin >> Pno;
    gets(Category);
    FixLocation();
}

void PIC::SeeAll() {
    cout << Pno << " " << Category << " " << Location << endl;
}

Question 3: What is the difference between the members in private visibility mode and the members in protected visibility mode inside a class? Also, give a suitable C++ code to illustrate both. [O.D, 2012]

Private members: Accessible only within the same class.
Protected members: Accessible within the same class and in derived classes.

class Me {
public:
    int a, b;

protected:
    int c, d; // Protected members

private:
    int e, f; // Private members
};

Short Answer Type Questions – II (3 Marks Each)

Question 1: Observe the following C++ code and answer the questions (i) and (ii). Assume all necessary files are included. [O.D, 2016]

class BOOK {
    long Code;
    char Title[20];
    float Price;
public:
    BOOK() {
        cout << "Bought" << endl;
        Code = 10;
        strcpy(Title, "NoTitle");
        Price = 100;
    }
    BOOK(int C, char T[], float P) {
        Code = C;
        strcpy(Title, T);
        Price = P;
    }
    void Update(float P) {
        Price += P;
    }
    void Display() {
        cout << Code << ":" << Title << ":" << Price << endl;
    }
    ~BOOK() {
        cout << "Book Discarded!" << endl;
    }
};

void main() {
    BOOK B, C(101, "Truth", 350);
    for (int I = 0; I < 4; I++) {
        B.Update(50);
        C.Update(20);
        B.Display();
        C.Display();
    }
}

(i) The concept illustrated by Function 1 and 2: Constructor Overloading / Polymorphism
(ii) Message “Book Discarded!” will be displayed: 2 times
Responsible line: Line 9 (end of main())

Question 2: Write the definition of a class CITY in C++ with the following description: [O.D, 2016]

class CITY {
    int CCode;
    char CName[20];
    long int Pop;
    float KM;
    float Density;

    void DenCal(); // Calculate Density = Pop / KM

public:
    void Record(); // Input values and call DenCal
    void View();   // Display values and check for population density
};

void CITY::DenCal() {
    Density = Pop / KM;
}

void CITY::Record() {
    cin >> CCode;
    gets(CName);
    cin >> Pop;
    cin >> KM;
    DenCal();
}

void CITY::View() {
    cout << CCode << " " << CName << " " << Pop << " " << KM << " " << Density << endl;
    if (Density > 10000)
        cout << "Highly Populated City" << endl;
}

Question 3: Write the definition of a class METROPOLIS in C++ with following description: [Delhi, 2016]

class METROPOLIS {
    int MCode;
    char MName[20];
    long int MPop;
    float Area;
    float PopDens;

    void CalDen() {
        PopDens = MPop / Area;
    }

public:
    void Enter() {
        cin >> MCode;
        cin.ignore();
        cin.getline(MName, 20);
        cin >> MPop;
        cin >> Area;
        CalDen();
    }

    void viewALL() {
        cout << MCode << " " << MName << " " << Area << " " << PopDens;
        if (PopDens > 12000)
            cout << " Highly Populated Area";
    }
};

Question 4: Answer the questions (i) to (iv) based on the following: [Delhi, 2016]

class PRODUCT {
    int Code;
    char Item[20];
protected:
    float Qty;
public:
    PRODUCT();
    void GetIn();
    void Show();
};

class WHOLESALER {
    int WCode;
protected:
    char Manager[20];
public:
    WHOLESALER();
    void Enter();
    void Display();
};

class SHOWROOM : public PRODUCT, private WHOLESALER {
    char Name[20];
public:
    SHOWROOM();
    void Input();
    void View();
};

(i) The inheritance used: Multiple Inheritance
(ii) Data members accessible by SHOWROOM objects: Name, Qty, Manager
(iii) Functions accessible through SHOWROOM objects: Input(), View(), GetIn(), Show()
(iv) Constructors invoked while creating SHOWROOM object: PRODUCT(), WHOLESALER(), SHOWROOM()

Question 5: Write the definition of a function Fixpay(float Pay[], int N) in C++: [O.D., 2016]

void Fixpay(float pay[], int N) {
    for (int i = 0; i < N; i++) {
        if (pay[i] < 100000)
            pay[i] += pay[i] * 0.35;
        else if (pay[i] < 200000)
            pay[i] += pay[i] * 0.30;
        else
            pay[i] += pay[i] * 0.20;
    }
}

Long Answer Type Questions

Question 1: Define a class Candidate in C++: [Delhi, 2015]

class Candidate {
    long Rno;
    char Cname[20];
    float Agg_marks;
    char Grade;

    void setGrade() {
        if (Agg_marks >= 80)
            Grade = 'A';
        else if (Agg_marks >= 65)
            Grade = 'B';
        else if (Agg_marks >= 50)
            Grade = 'C';
        else
            Grade = 'D';
    }

public:
    Candidate() {
        Rno = 0;
        strcpy(Cname, "N.A.");
        Agg_marks = 0.0;
    }

    void Getdata() {
        cout << "Registration No: "; cin >> Rno;
        cout << "Name: "; cin >> Cname;
        cout << "Aggregate Marks: "; cin >> Agg_marks;
        setGrade();
    }

    void dispResult() {
        cout << "Registration No: " << Rno << endl;
        cout << "Name: " << Cname << endl;
        cout << "Aggregate Marks: " << Agg_marks << endl;
        cout << "Grade: " << Grade << endl;
    }
};

Question 2: Define a class Customer with the following specifications: [CBSE SQP 2015]

class Customer {
    int Customer_no;
    char Customer_name[20];
    int Qty;
    float Price, TotalPrice, Discount, Netprice;

public:
    Customer() {
        Customer_no = 111;
        strcpy(Customer_name, "Leena");
        Qty = 0;
        Price = Discount = Netprice = 0;
    }

    void Input() {
        cin >> Customer_no;
        cin.ignore();
        cin.getline(Customer_name, 20);
        cin >> Qty >> Price;
        Caldiscount();
    }

    void Caldiscount() {
        TotalPrice = Price * Qty;
        if (TotalPrice >= 50000)
            Discount = 0.25 * TotalPrice;
        else if (TotalPrice >= 25000)
            Discount = 0.15 * TotalPrice;
        else
            Discount = 0.10 * TotalPrice;
        Netprice = TotalPrice - Discount;
    }

    void Show() {
        cout << "Customer No: " << Customer_no << endl;
        cout << "Name: " << Customer_name << endl;
        cout << "Qty: " << Qty << endl;
        cout << "Total Price: " << TotalPrice << endl;
        cout << "Net Price: " << Netprice << endl;
    }
};

Question 3: Define a class CONTEST:

class CONTEST {
    int Eventno;
    char Description[30];
    int Score;
    char Qualified;

public:
    CONTEST() {
        Eventno = 11;
        strcpy(Description, "School level");
        Score = 100;
        Qualified = 'N';
    }

    void Input() {
        cin >> Eventno;
        cin.ignore();
        cin.getline(Description, 30);
        cin >> Score;
    }

    void Award(int cutoffscore) {
        Qualified = (Score > cutoffscore) ? 'Y' : 'N';
    }

    void Displaydata() {
        cout << "Event No: " << Eventno << endl;
        cout << "Description: " << Description << endl;
        cout << "Score: " << Score << endl;
        cout << "Qualified: " << Qualified << endl;
    }
};

Question 4: Derive class 'District' from 'State':

class State {
protected:
    int tp;

public:
    State() {
        tp = 0;
    }

    void inctp() {
        tp++;
    }

    int gettp() {
        return tp;
    }
};

class District : public State {
private:
    char distname[50];
    long population;

public:
    void dinput() {
        cin.ignore();
        cin.getline(distname, 50);
        cin >> population;
    }

    void doutput() {
        cout << "District Name: " << distname << endl;
        cout << "Population: " << population << endl;
    }
};

Question 5: Define a function Fixpay(float Pay[], int N) in C++ to modify the salary array according to the given rules.

void Fixpay(float Pay[], int N) {
    for (int i = 0; i < N; i++) {
        if (Pay[i] < 100000)
            Pay[i] += Pay[i] * 0.35;
        else if (Pay[i] >= 100000 && Pay[i] < 200000)
            Pay[i] += Pay[i] * 0.30;
        else
            Pay[i] += Pay[i] * 0.20;
    }
}

Question 6: Candidate Class Define a class Candidate in C++ with the following specifications:

class Candidate {
    long Rno;
    char Cname[20];
    float Agg_marks;
    char Grade;

    void setGrade() {
        if (Agg_marks >= 80)
            Grade = 'A';
        else if (Agg_marks >= 65)
            Grade = 'B';
        else if (Agg_marks >= 50)
            Grade = 'C';
        else
            Grade = 'D';
    }

public:
    Candidate() {
        Rno = 0;
        strcpy(Cname, "N.A");
        Agg_marks = 0.0;
    }

    void Getdata() {
        cout << "Enter Registration Number: ";
        cin >> Rno;
        cout << "Enter Name: ";
        cin >> Cname;
        cout << "Enter Aggregate Marks: ";
        cin >> Agg_marks;
        setGrade();
    }

    void dispResult() {
        cout << "Registration No: " << Rno << endl;
        cout << "Name: " << Cname << endl;
        cout << "Aggregate Marks: " << Agg_marks << endl;
        cout << "Grade: " << Grade << endl;
    }
};

Question 7: Customer Class Define a class Customer with the following specifications:

class Customer {
    int Customer_no;
    char Customer_name[20];
    int Qty;
    float Price, TotalPrice, Discount, Netprice;

public:
    Customer() {
        Customer_no = 111;
        strcpy(Customer_name, "Leena");
        Qty = 0;
        Price = 0;
        Discount = 0;
        Netprice = 0;
    }

    void Input() {
        cout << "Enter Customer No: ";
        cin >> Customer_no;
        cout << "Enter Customer Name: ";
        gets(Customer_name);
        cout << "Enter Quantity: ";
        cin >> Qty;
        cout << "Enter Price: ";
        cin >> Price;
        Caldiscount();
    }

    void Caldiscount() {
        TotalPrice = Price * Qty;
        if (TotalPrice >= 50000)
            Discount = 0.25 * TotalPrice;
        else if (TotalPrice >= 25000)
            Discount = 0.15 * TotalPrice;
        else
            Discount = 0.10 * TotalPrice;
        Netprice = TotalPrice - Discount;
    }

    void Show() {
        cout << "Customer No: " << Customer_no << endl;
        cout << "Customer Name: " << Customer_name << endl;
        cout << "Quantity: " << Qty << endl;
        cout << "Total Price: " << TotalPrice << endl;
        cout << "Net Price: " << Netprice << endl;
    }
};

Question 8: Contest Class Define a class CONTEST with the following description:

class CONTEST {
private:
    int Eventno;
    char Description[30];
    int Score;
    char Qualified;

public:
    CONTEST() {
        Eventno = 11;
        strcpy(Description, "School level");
        Score = 100;
        Qualified = 'N';
    }

    void Input() {
        cout << "Enter Event No: ";
        cin >> Eventno;
        cout << "Enter Description: ";
        gets(Description);
        cout << "Enter Score: ";
        cin >> Score;
    }

    void Award(int cutoffscore) {
        if (Score > cutoffscore)
            Qualified = 'Y';
        else
            Qualified = 'N';
    }

    void Displaydata() {
        cout << "Event No: " << Eventno << endl;
        cout << "Description: " << Description << endl;
        cout << "Score: " << Score << endl;
        cout << "Qualified: " << Qualified << endl;
    }
};

Question 9: District Class Consider the following State class. Write a derived class District to inherit the state data and include additional members.

class State {
protected:
    int tp;
public:
    State() {
        tp = 0;
    }
    void inctp() {
        tp++;
    }
    int gettp() {
        return tp;
    }
};

class District : public State {
private:
    char distname[50];
    long population;
public:
    void dinput() {
        cout << "Enter District Name: ";
        gets(distname);
        cout << "Enter Population: ";
        cin >> population;
    }

    void doutput() {
        cout << "District Name: " << distname << endl;
        cout << "Population: " << population << endl;
    }
};

Question 10: CABS Class Define a class CABS to manage a cab system with the following specifications:

class CABS {
    int CNo;
    char Type;
    int PKM;
    float Dist;

public:
    CABS() {
        Type = 'A';
        CNo = 1111;
    }

    void Charges() {
        if (Type == 'A') PKM = 25;
        else if (Type == 'B') PKM = 20;
        else if (Type == 'C') PKM = 15;
    }

    void Register() {
        cout << "Enter Cab No: ";
        cin >> CNo;
        cout << "Enter Type (A/B/C): ";
        cin >> Type;
        Charges();
    }

    void ShowCab() {
        cout << "Enter Distance: ";
        cin >> Dist;
        cout << "Cab No: " << CNo << endl;
        cout << "Type: " << Type << endl;
        cout << "PKM: " << PKM << endl;
        cout << "Amount: " << PKM * Dist << endl;
    }
};

Question 11: Find the output of the following program:

#include <iostream.h>

class METRO {
    int Mno, TripNo, PassengerCount;
public:
    METRO(int Tmno = 1) {
        Mno = Tmno;
        TripNo = 0;
        PassengerCount = 0;
    }

    void Trip(int PC = 20) {
        TripNo++;
        PassengerCount += PC;
    }

    void StatusShow() {
        cout << Mno << " : " << TripNo << " : " << PassengerCount << endl;
    }
};

void main() {
    METRO M(5), T;
    M.Trip();
    T.Trip(50);
    M.StatusShow();
    M.Trip(30);
    T.StatusShow();
    M.StatusShow();
}

Output:
5 : 1 : 20
1 : 1 : 50
5 : 2 : 50

Question 12: RESTRA Class Define a class RESTRA in C++ with the following description:

class RESTRA {
    char FoodCode;
    char Food[20], FType[20], Sticker[20];

    void GetSticker() {
        if (strcmp(FType, "Vegetarian") == 0)
            strcpy(Sticker, "GREEN");
        else if (strcmp(FType, "ContainsEgg") == 0)
            strcpy(Sticker, "YELLOW");
        else if (strcmp(FType, "Non-Vegetarian") == 0)
            strcpy(Sticker, "RED");
    }

public:
    void GetFood() {
        cout << "Enter FoodCode, Food, Food Type: ";
        cin >> FoodCode;
        gets(Food);
        gets(FType);
        GetSticker();
    }

    void ShowFood() {
        cout << "Enter Food Code, Food, FoodType, Sticker:" << endl;
        cout << FoodCode << endl;
        puts(Food);
        puts(FType);
        puts(Sticker);
    }
};

Question 13: Find the output of the following program:

#include <iostream.h>

class TRAIN {
    int Tno, TripNo, PersonCount;

public:
    TRAIN(int Tmno = 1) {
        Tno = Tmno;
        TripNo = 0;
        PersonCount = 0;
    }

    void Trip(int TC = 100) {
        TripNo++;
        PersonCount += TC;
    }

    void show() {
        cout << Tno << " : " << TripNo << " : " << PersonCount << endl;
    }
};

void main() {
    TRAIN T(10), N;
    N.Trip();
    T.show();
    N.Trip(70);
    N.Trip(40);
    N.show();
    T.show();
}

Output:
10 : 0 : 0
1 : 2 : 140
10 : 0 : 0

Question 14: Candidate Class Define a class Candidate in C++ with the following description:

class Candidate {
    long RNo;
    char Name[40];
    float Score;
    char Remarks[20];

    void AssignRem() {
        if (Score >= 50) {
            strcpy(Remarks, "Selected");
        } else {
            strcpy(Remarks, "Not Selected");
        }
    }

public:
    void Enter() {
        cout << "Enter the values for RNo, Name, Score: ";
        cin >> RNo;
        gets(Name);
        cin >> Score;
        AssignRem();
    }

    void Display() {
        cout << RNo << " " << Score << endl;
        puts(Name);
        puts(Remarks);
    }
};

Question 15: Applicant Class Define a class Applicant in C++ with the following description:

class Applicant {
    long ANo;
    char Name[40];
    float Agg;
    char Grade;

    void GradeMe() {
        if (Agg >= 80) Grade = 'A';
        else if (Agg >= 65) Grade = 'B';
        else if (Agg >= 50) Grade = 'C';
        else Grade = 'D';
    }

public:
    void Enter() {
        cout << "Enter the values for ANo, Name, Agg: ";
        cin >> ANo;
        gets(Name);
        cin >> Agg;
        GradeMe();
    }

    void Result() {
        cout << ANo << " " << Agg << endl;
        puts(Name);
        cout << Grade << endl;
    }
};

Question 16: ITEM Class Define a class ITEM in C++ with the following description:

class Item {
    int Code;
    char Iname[20];
    float Price;
    int Qty;
    float Offer;

    void GetOffer() {
        if (Qty <= 50) {
            Offer = 0;
        } else if (Qty <= 100) {
            Offer = 5; // Or Offer = 0.05;
        } else {
            Offer = 10; // Or Offer = 0.1;
        }
    }

public:
    void GetStock() {
        cin >> Code;
        gets(Iname);
        cin >> Price >> Qty;
        GetOffer();
    }

    void ShowItem() {
        cout << Code << " " << Iname << " " << Price << " " << Qty << " " << Offer << endl;
    }
};

Question 17: Stock Class Define a class Stock in C++ with the following description:

class Stock {
    int ICode, Qty;
    char Item[20];
    float Price, Discount;

    void FindDisc() {
        if (Qty <= 50) {
            Discount = 0;
        } else if (Qty <= 100) {
            Discount = 5; // Or Discount = 0.05;
        } else {
            Discount = 10; // Or Discount = 0.1;
        }
    }

public:
    void Buy() {
        cin >> ICode;
        gets(Item);
        cin >> Price >> Qty;
        FindDisc();
    }

    void ShowAll() {
        cout << ICode << '\t' << Item << '\t' << Price << '\t' << Qty << '\t' << Discount << endl;
    }
};

Short Answer Type Questions – 1 (2 Marks Each)

Question 1: Answer the questions (i) and (ii) after going through the following class:

class Hospital {
    int Pno, Dno;
    public:
    Hospital(int PN);             //Function 1
    Hospital();                   //Function 2
    Hospital(Hospital &H);        //Function 3
    void In();                    //Function 4
    void Disp();                  //Function 5
};

void main() {
    Hospital H(20);               //Statement 1
}

(i) Which function will get executed when Statement 1 is executed?

Answer: Function 1 will get executed.
Explanation: The statement Hospital H(20); invokes the parameterized constructor Hospital(int PN), which is Function 1.

(ii) Write a statement to declare a new object G with reference to already existing object H using Function 3.

Answer: Hospital G(H);
Explanation: This creates a new object G by copying the state of object H using the copy constructor Hospital(H), which is Function 3.

Question 2: Answer the questions (i) and (ii) after going through the following class:

class Health {
    int PId, Did;
public:
    Health(int PPID);             //Function 1
    Health();                     //Function 2
    Health(Health &H);            //Function 3
    void Entry();                 //Function 4
    void Display();               //Function 5
};

void main() {
    Health H(20);                //Statement 1
}

(i) Which function will get executed when Statement 1 is executed?

Answer: Function 1 will get executed.
Explanation: The statement Health H(20); invokes the constructor Health(int PPID), which is Function 1.

(ii) Write a statement to declare a new object G with reference to already existing object H using Function 3.

Answer: Health G(H);
Explanation: This statement uses the copy constructor to create a new object G using the existing object H.

Question 3: What is the relationship between a class and an object? Illustrate with a suitable example.

Answer: A class is a blueprint or template that defines the structure and behavior of objects. An object is an instance of a class, holding actual values for the class attributes and using its methods.

Example:

class Box {
    int length, breadth, height;
public:
    void SetDimensions(int l, int b, int h) {
        length = l;
        breadth = b;
        height = h;
    }
    void Display() {
        cout << "Length: " << length 
             << ", Breadth: " << breadth 
             << ", Height: " << height << endl;
    }
};

int main() {
    Box a;  // 'a' is an object of class Box
    a.SetDimensions(10, 20, 30);
    a.Display();
    return 0;
}