Fundamentals of Programming - Notes

Question 1

How are stack frames used by computers

Answer 1

To store return address, parameters and local variables for each subroutine call that occurs during the execution of a program

Question 2

How does exception handling work

Answer 2

-When an error occurs, the computer has to handle that error to avoid crashing
-It pauses execution and saving the current state of the program
-Runs the catch block of code
-Once error has been handled, the program restores its previous state before resuming execution

Question 3

When does polymorphism occur

Answer 3

When a method in an object is processed differently depending on the class

Question 4

Two types of association:

Answer 4

Aggregration and Composition

Question 5

Relationship of Aggregration

Answer 5

Weak as an associated object will still exist when an object is deleted

Question 6

Relationship of Composition

Answer 6

Strong as when an object is deleted, the associated object is also deleted

Question 7

Whats an abstract method

Answer 7

Declared in the abstract class and do not have an implementation, they serve as a blueprint for methods that must be implemented by a subclass. Ensuring consistency between different subclasses.

Question 8

Whats a virtual method

Answer 8

Methods in a base class that can be overriden by derived classes. They faciliate polymorphism, enabling method behaviour to vary based on the objects that invokes the method.

Question 9

Encapsulate what varies definition

Answer 9

When designing a program, any requirements which are likely to change in the future should be encapsulated in a class so that any changes can be easily made when required

Question 10

Favour composition over inheritance

Answer 10

Wherever possible, composition should be used over inheritance as composition is seen to have a more flexible relationship over objects

Question 11

Program to interfaces, not implementation

Answer 11

This design principle allows unrelated classes to make use of similar methods. An interface is defined as a collection of abstract procedures that can be implemented by unrelated classes

Question 12

How is aggregration and composition drawn

Answer 12

Aggregration : weaker so unfilled diamond arrow head
Composition : stronger so filled diamond arrow head

Question 13

Benefit of principle ‘Favour composition over inheritance’

Answer 13

Easier to test each class using unit testing
There can be unintended side effects for derived classes if a base class is altered.