Programming

Question 1

What happens when a variable is declared?

Answer 1

1. The compiler is told the data type for the values being stored (so that it knows how much space to reserve)
2. The compiler is being told the identifier that you will be using to refer to that space in memory

Question 2

What are constants and how do they work?

Answer 2

Constants are named references to literal values. When the program is complied, any references to the constants are replaced by actual values in machine code.

Question 3

What are the benefits of using constants?

Answer 3

• The code becomes easier to understand as descriptive labels are used instead of values
• The code is easier to maintain as a constant’s value can be changed in one place

Question 4

What is a global scope?

Answer 4

It can be referred to anywhere in the program

Question 5

What are features of local variables?

Answer 5

• Their value cannot be accessed or modified from outside the subroutine
• Their identifier can be reused in other subroutines
• only stored in memory when the subroutine is being executed

Question 6

What is a parameter in a subroutine?

Answer 6

Part of the subroutine’s interface that allows values to be passed into the subroutine when it is called

Question 7

What is an argument in a subroutine?

Answer 7

Value passed to a subroutine via a parameter

Question 8

What is passing by value?

Answer 8

A literal value or copy of a data structure is given to the subroutine. A change made to this copy does not have any effect on the original.

Question 9

What is passing by reference?

Answer 9

The subroutine is given a pointer to the address of the value/object in memory. If changes are made to the referenced value or data structure, they change the original so the change persists after the subroutine has finished.

Question 10

What is exception handling?

Answer 10

Allows programmers to decide how a program should respond to the occurrence of an error that would otherwise lead to the program terminating abruptly.

Question 11

What is a programming paradigm?

Answer 11

An approach to programming

Question 12

What is procedural programming?

Answer 12

Type of imperative programming where programs are made up of “imperatives” what are run step-by-step

Question 13

What does the structural approach to programming involve?

Answer 13

• Organising into subroutines and modules
• Using hierarchy charts to break programs down
• Storing data in variables and constants that have meaningful identifiers
• Programming to the interface
• Using local variables instead of global ones
• Using indentations, spacing and comments to make code easier to follow

Question 14

What are the advantages to the structured approach?

Answer 14

• Subroutines and modules can be individually tested
• Modules contains code for related subroutines helping developers find and identify the code they need
• Indented code is easier to read
• Comments explain how the program works
• Meaningful identifiers make the code easier to understand

Question 15

What is a hierarchy chart?

Answer 15

• A diagram showing the structure of a program using a top-down approach
• Breaks system down layer-by-layer into components and processes
• Each box contains a label / description for each process

Question 16

What are the advantages of subroutines?

Answer 16

• Each subroutine can be tested separately
• Meaningful identifiers make the code easier to understand
• Code easily reused
• Easier to maintain as code only needs to be changed once within the subroutine

Question 17

What is a class?

Answer 17

The definition of an object. Classes define the attributes and methods that an object of the class will have.

Question 18

What is an object?

Answer 18

A specific instance of a class resident in memory

Question 19

What is instantiation?

Answer 19

The process of creating an instance of an object, belonging to a class, by invoking a constructor method

Question 20

What is encapsulation?

Answer 20

Combing data with the procedures and functions that manipulate it to form a new data type

Question 21

What are the properties of OOP?

Answer 21

• Entirely modular approach
• Everything implemented as objects composed of attributes/properties and methods
• Data and code that acts on the data are kept together and controlled via methods that comprise the interface

Question 22

What is information hiding?

Answer 22

Protects an object’s implementation and internal state from being accessed by other objects

Question 23

What are the uses of information hiding?

Answer 23

Allows programmers to implement restrictions on how values are accessed and set. This is done through the use of access modifiers.

Question 24

What are the access modifiers and their descriptions?

Answer 24

• Public: accessed by objects of any other class (+)
• Private: accessed only by objects of that class (-)
• Protected: accessed by other objects of the class or subclass (#)

Question 25

What is a getter method?

Answer 25

A method that returns the requested attribute value

Question 26

What is a setter method?

Answer 26

A method that can modify the attribute’s value

Question 27

Why do we use getters and setters?

Answer 27

They allow developers to implement additional checks before accepting or providing data.

Question 28

What is inheritance?

Answer 28

Describes the relationship between classes where a derived “child” class gains the attributes and methods from a “parent” class

Question 29

What is polymorphism?

Answer 29

When objects of different classes respond differently to the use of a common interface

Question 30

What is the interface?

Answer 30

The collection of a classes public methods, attributes and its identifier

Question 31

What is overriding?

Answer 31

- When a method is defined in a derived class with the same identifier as a method from the base class but is given a different implementation/ performs a different function - Redefined method will be used instead of the base’s method when called

Question 32

What are methods that can be overridden by a derived class called?

Answer 32

Virtual methods

Question 33

What does an abstract method define?

Answer 33

The interface: - identifier - return type - list of parameters

Question 34

What are the differences between a virtual and abstract class?

Answer 34

- Virtual can be overridden but abstract must be overridden - Virtual have an implementation but abstract do not - Virtual can be declared in any class but abstract can only be defined in abstract classes

Question 35

What is object association?

Answer 35

Occurs when an object contains or has a reference to another object within it. Often described as a “has a” relationship.

Question 36

What are the two forms of association?

Answer 36

- Composition - “strong” - Aggregation - “weak”

Question 37

What is composition?

Answer 37

It is a restricted form of association where one object contains another. If the container object is deleted, the contained object/s are also deleted.

Question 38

How is composition shown on a UML class diagram?

Answer 38

A line with a solid black diamond on the container

Question 39

What is aggregation?

Answer 39

Type of relationship where one class contains another class. However the aggregated objects independently of the aggregating object and will not be deleted if the aggregating object is.

Question 40

How do you represent aggregation in UML class diagrams?

Answer 40

A line with a hollow diamond on the aggregating

Question 41

How do you represent inheritance in a UML class diagram?

Answer 41

A filled arrow going from the derived class to the base class

Question 42

What are the 3 OOP design principles?

Answer 42

1. Encapsulate what varies 2. Favour composition over inheritance 3. Program to the interface, not implementation

Question 43

What does the design principle “encapsulate what varies” mean?

Answer 43

- Encapsulate parts of our program that frequently changed or updated into classes - Ensures modules are loosely-coupled - Modifications can be tested within the class itself and has minimal impact on the rest of the program

Question 44

What does the design principle “favour composition over inheritance” mean?

Answer 44

- Composition isn more flexible and allows for complex functionalities by combining component objects - If class A requires functionality of class B, it is best to give class A an instance of class B rather than inheriting from it

Question 45

What does the design principle “program to the interface, not implementation” mean?

Answer 45

- To write loosely-coupled code our objects should be designed to only interact with other objects via their interface - This allows for implementation to be changed without affecting the rest of the program

Question 46

What is a static method?

Answer 46

A class method that can be called / invoked without the need to instantiate and object of that class

Question 47

What are the uses of static methods?

Answer 47

- Provide functionality that is related to a class but doesn’t rely on the internal state of an instance of a class - Used for creating “Utility Classes” that creates lots of utility classes