C++ Flashcards
What does C++ add to C?
- Classes
- Exception handling
- Function & operator overloading
- Default values for parameters
- Pass by reference
What is ::?
Scope resolution operator
What removes the need for the scope resolution operator?
“using namespace std”
What does cout and cerr do?
cout: goes to stdout
cerr: goes to stderr
Why must two functions that are identical in all but input types be created?
They may result in different return types
In a .hpp class, what are the two key elements that define a class?
- Private class variables
- Public member function prototypes
What are the three access specifiers in a class?
- Private (default): can only be accessed within the class
- Public: can be accessed by any part of the program
- Protected: To do with inheritance
Where are functions for a class defined?
In a .cpp file with the same name as the .hpp file
How is a class used in a C++ file?
include <headerfilename.hpp></headerfilename.hpp>
What can be done if you have a class that can take a varying number of parameters?
Use overloading:
NewClass(int, int)
NewClass(int)
This is valid as there are a differing number of arguments
What values can be defaulted in a class function?
Only the trailing parameters
void NewClass::someFunction(int i, int j=0) (VALID)
void NewClass::someFunction(int i=1, int j=0) (VALID)
void NewClass::someFunction(int i=1, int j) (INVALID)
How has malloc been replaced in C++?
Instead of:
“int *p = (int )malloc(sizeof(int)25);
free(p);
It is now:
int *p = new int; // a single integer, uninitialised
int *p = new int(43); // a single integer, initialised to value 43
int *p = new int[25]; // an array of 25 integers
delete p; // free the single value p
delete[] p; // free the array p
What are constructors and destructors of a class?
They can be implicitly called when a object of the class type has been created or destroyed (i.e. when return 0 is stated). The constructor malloc memory to pointers and the destructor frees memory allocated to pointers.
What is a reference?
A reference is an alias for a variable
int num = 43;
int &ref = num;
ref = 43;
What is ‘this’?
‘this’ is a pointer to a current object and used to avoid ambiguities if you want to pass the object to a function or tor return a reference to the calling object
What is a copy constructor?
A member function that initialises an object using another object of the same class
MyClass (const MyClass &)
MyClass c, d;
MyClass e = c; // calls the copy constructor
d = e; // calls an assignment operator not the copy constructor
What is a static member variable?
- They are shared by all objects of the same class
- Can be accessed even if no objects exist
What is inheritance?
When a class uses another class’s protected and public functions/attributes as well as its own
What effect do access specifiers have on inherited classes?
If either the base class or inheritance member access specifier is protected then the derivied class effect is protected. The same for private.
What are the rules for constructors and destructors?
- Constructors are executed in order of derivation
- Destructors are executed in reverse order of derivation
What is the diamond problem?
It is do with multiple inheritance. If there are two derived classes from the same class, and a class that derives from both of them, what happens if this class tries to access a variable from the original class.
What are the two solutions to the diamond problem?
- Apply the scope resolution operator
- Prevent two copies of the base class being included in the bottom class (this can be done using a virtual class)
What is a friend function in relation to a class?
- A non-member function (not a member of the class)
- Has access to the private and protected elements of the class
- It is preceded by ‘friend’ in the public modifier
What is friendship NOT?
- Inherited
- Transitive
