Call constructor from base class : class hierarchy « Class « C++ Tutorial

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2. Class
3. class hierarchy

#include <iostream>
using namespace std;

class MyType {

protected:
       float value;

public:
         float subtract(float);
         float add(float);
         void display();
         MyType(float);
         MyType();
};

MyType::MyType(float num)
{
   value = num;
}
MyType::MyType()
{
   value = 1000;
}

float MyType::subtract(float amount)
{

    value -= amount;
       return value;
}
float MyType::add(float amount)
{
    value += amount;
       return value;
}

void MyType::display()
{
  cout << "Your value is " << value << endl;
}

class DerivedType:public MyType
{

public:
       DerivedType(float);
};

DerivedType::DerivedType(float num):MyType(num)
{

}



DerivedType myType(1200);

int main()
{

  float amount, balance;

  myType.display();
  cout << endl;
  cout << "Please enter the amount to deposit \n";
  cin>> amount;
  balance = myType.add(amount);
  cout << "New balance is " << balance << endl;
  cout << endl;

  cout << "Please enter the amount to withdraw \n";
  cin >> amount;
  balance = myType.subtract(amount);
  cout << "New balance is " << balance << endl;
  cout << endl;

  return 0;
}

Your value is 1200

Please enter the amount to deposit
123
New balance is 1323

Please enter the amount to withdraw
123
New balance is 1200