Midterm Exam Programme

You need to be able to answer the following questions in detail. Each question should evoke an example (usually, a few lines of code) in your mind.

1. Constructors, destructors, copy constructors.
   • What is the difference between private and public members of a class? What is the basic difference between a C++ struct and a C++ class?
   • What is a constructor?
   • What is a default constructor? Give an example when writing an explicit default constructor is necessary.
   • What is a copy constructor? How does the compiler decide which of the constructors described in a class (if any) is a copy constructor (if any)? Give an example when writing an explicit copy constructor is necessary. What happens if you don't write an explicit copy constructor?
   • The same for operator= (also see overloading)
   • What is the connection between copy constructors and arguments passed to functions? What is the difference between the operation of
     void foo( X a );
     void foo( X & a );
     void foo( const X & a );
     and what can you tell about what foo can do to an object of type X passed to it as an argument (in particular, can foo change it?)
   • Why are objects of a type X so often passed to functions as const X & (const reference to X) ?
   • Write an example of code that passes an object to a function by reference (so that the function can change the value of the variable it is given as an argument) using only (1) references & (2) pointers .
   • What is a temporary object? How do you create cause a temporary to be created? How long is it guaranteed to exist?
   • What is a destructor? When are destructors called? Give an example of when you have to write a destructor explicitly.
   • Can you create an object in a function and return a reference to it?
   • Name the four methods (member functions) that are generated by default for each class you declare. When can you hope that those default methods do what you intend?
   • What is the difference between member functions of a class and friend functions of a class? What is the syntax for declaring a function as a friend of a class?
   • Can an instance of class (e.g. a variable of that type) find what place in memory it occupies? Why knowing this may be useful?
2. Overloading
   • What is type checking? What role it plays in the work of a C++ compiler?
   • What is overloading? Why use it?
   • Describe how the compiler chooses the right function to compile into your code out of several functions with the same name.
   • What are overloaded operators? Give an example from a standard library.
   • Why and how does cout << x; know to print an integer x differently than a double x, differently than a string x? Is operator<< usually a friend or a member of a class? Of which class can it be a member?
   • Why binary operators are usually friends, while unary operators are usually members?
   • Write a class that represents time -- days, hours, minutes, seconds -- by keeping each of the above as separate data members, and implements operator+ , operator<< etc.
   • Should an overloaded operator+ return a new object or a reference? Should an overloaded operator= return a new object or a reference?
   • What is a type conversion operator? How do you create one for your own class?
3. Dynamic memory allocation and container classes.
   • Why use dynamic memory? Give an example when it is necessary.
   • How do you request memory at run-time? How do you allocate and initialize (1) an object (2) an array of objects ?
   • What happens it you don't free up (how?) the memory allocated with new[] ?
   • Describe what problems can arise if a class that holds pointers to dynamically allocated memory does not have an explicit copy constructor and operator= .
   • Explain the operation of a self-expanding table (see my Table example).
   • Implement your own string class that can handle strings of arbitrary length (i.e. the only limitation is the size of available memory) Concentrate on the copy constructor, operator+ and operator= . (In particular, if a, b, c are strings, c = b; b = a; a = c; should swap the values of a and b .)