midterm

Question 1

What is an incomplete declaration?

Answer 1

• The keyword “class” in front of the base class name is called an incomplete declaration and allows classes to be used before they are defined

Question 2

Describe function “Hiding”.

How you you access hidden functions?

Answer 2

Derived class methods (eg., member functions) that are of the same name as the base class’ methods “hide” the base class’ version of the function.

The base class’ public function can be called using the class name and scope resolution operator from outside the class:

      object.base::function(argument_list);

• The base class’ public or protected function can be called using the class name and scope resolution operator from a derived class’ member function:

       base::function(argument_list);

Question 3

When MUST initialization lists be used?

Why is the order of initialization important?

Answer 3

Initialization lists must be used to
- initialize any constant data members
-to cause the base class’ constructor to be invoked when
working with constructors with arguments.

The order of the items in the initialization list is important. The base class constructor must be specified first, followed by the data members that you elect to initialize. The order that data members are initialized is based on the order in which memory is allocated and the order in which constructors are invoked.

Question 4

3. What does the & operator do?

Answer 4

3. The & operator, called the Address Operator, gets the address location of a variable, not its value.

Question 5

What are the 3 rules of recursion?

Answer 5

1. A recursive algorithm must have a base case.
2. A recursive algorithm must change its state and move toward the base
   case.
3. A recursive algorithm must call itself, recursively.

Question 6

What is the difference between pass by value and pass by reference?

Answer 6

By definition, pass by value means you are making a copy in memory of the actual parameter’s value that is passed in, a copy of the contents of the actual parameter. Use pass by value when when you are only “using” the parameter for some computation, not changing it for the client program.

In pass by reference (also called pass by address), a copy of the address of the actual parameter is stored. Use pass by reference when you are changing the parameter passed in by the client program.

When you pass a pointer as parameter, you actually implement the pass by reference paradigm yourself, as in C. Because when you modify the data in the specified address, you exactly modify the object in the caller function.

funct(int arg); // pass by value

funct(int & arg); pass by reference

funct(int * arg); pass by reference

Question 7

1. What causes a Copy Constructor to be invoked?

2. What Is the prototype syntax for a copy constructor?

Answer 7

1. A new object is created and initialized to an existing object of the same kind.
2. class_name(const class_name &class_object);

Question 8

What relationships are available in OOP?

Answer 8

• Using
• Containing (“has a”),
• Specialization (“Inheritance” or “Is a”); The benefit of specialization is that we can avoid the need to
build wrapper functions to gain access to the contained object, simplifying the code!

Question 9

What is the syntax for deriving a class from a base class?

Answer 9

class Derived: public Base { /* body */}
or
class Derived: public class Base { /* body */}

Question 10

1. What does a pointer do?

Answer 10

1. A pointer holds the address of a value.

Question 11

2. What does the * operator do? What other names are associated with it?What is a base case?

Answer 11

2. The * operator yields the value at that address location. This value is the
   Indirect Value. It is also called the Dereferencing Operator.

Question 12

What is a base case?

Answer 12

The base case, or halting case, of a function is the problem that we know the answer to, that can be solved without any more recursive calls. The base case is what stops the recursion from continuing on forever. Every recursive function must have at least one base case (many functions have more than one).

Question 13

What can access protected members of a class?

Answer 13

Protected members are accessible by derived class but not by clients or classes that are not derived.

Question 14

How do you invoke a base class’s copy constructor that needs arguments?

Answer 14

the only way to cause a base class’ constructor with arguments to be used is for
a derived class to specify the constructor “invocation” via an initialization list

Question 15

When should you make a member function “const”?

What is the syntax?

Answer 15

When writing member functions that don’t modify the data members, make those
member functions “constant” member functions.

This can be done via:
               //notice the placement of the const keyword

           void display() const;

Question 16

what is a shallow copy?

What is another name for a shallow copy?

Answer 16

The data members of one object are copied into the data members of another object without taking any dynamic memory pointed to by those data members into consideration.

(“memberwise copy”)

Question 17

What is a deep copy?

Answer 17

Any dynamic memory pointed to by the data members is duplicated and the contents of that memory is copied (via copy constructors and assignment operators – when overloaded)

Question 18

When is a memberwise copy OK?

Answer 18

In situations where pointers are not members of a class, memberwise copy is an adequate operation for copying objects.

Question 19

Name three situations when we need deep copy

Answer 19

– initialize an object with the value of another object:

name s1; name s2(s1);

– pass an object by value to a function or when we return by value:

name function_proto (name)

– assign one object to another:
s1 = s2;