classes in C++

Question 1

using classes in C++

Answer 1

• inside class, members referred to by name
• outside class, full name of member used
(i.e. class-name::Member name)

Question 2

what are overloaded functions?

Answer 2

functions with different implementations based on the number and/or types of arguments

Question 3

dynamic memory allocation in C++

Answer 3

• new T create a new instance of type T and returns a pointer to it (new also calls any constructor)
• delete x calls any destructor then deallocates memory

Question 4

pointers

Answer 4

• if x is an object, x.y refers to member y of x
• if x is a pointer, x->y refers to member y of object pointer to by x
• “this” is a pointer to the object for which the function was called (only legal in member function)

Question 5

what is inheritance?

Answer 5

the reuse of code and variables in a derived class

C++ supports inheritance and multiple inheritance

Question 6

C++ supports three access modifiers

Answer 6

1) public - anyone can access
2) private - only this class can access
3) protected - this class and its subclasses can access

Question 7

what is polymorphism?

Answer 7

• ability to use a subclass where a superclass is expected
• functions of the subclass are invoked (rather than those of superclass)
• C++ supports it (only functions marked as virtual are polymorphic)
• a run-time thing

Question 8

what are templates?

Answer 8

• another way to achieve reuse is through genericity
• achieved through parameterized types
• happens at compile time
• each use of a template with a different type parameter creates a new type at run-time

Question 9

pros and cons of templates

Answer 9

• no runtime expense
• catch more errors at compile time (good)
• programs suffer from code bloat

Question 10

two ways to give re-use

Answer 10

polymorphism: errors aren’t caught until run-time, slower code
templates: catch more errors at compile-time, suffers from code bloat