2.2.1 - Programming Techniques

Question 1

What is a variable?

Answer 1

Identifier/name of a memory location used to store data

Used to store a value which can change during execution

Question 2

What are the global variables?

Answer 2

The variable can be accessed throughout the scope of the program (visible throughout a program)

Using passing by reference is an equivalent of a global variable.

Question 3

What are the negatives of global variables?

Answer 3

Global variables mean that memory space is kept throughout the running of the program, not just the sub-program (which uses more space than local)

Make it difficult to track changes as it can be changed from any other part of the code.

Question 4

What is a local variable?

Answer 4

Can only be accessed within the scope of the sub-program where it is created

A parameter that is passed into a subroutine becomes a local variable in the subroutine e.g. LoadLevel(Difficulty)

Question 5

What is an IDE?

Answer 5

Integrated Development Environment (IDE) - A program used for developing programs, made from several components.

Question 6

What tools are provided by an IDE to develop software?

Answer 6

• Auto-complete – Will predict variable and built-in functions and finish off the word. Can avoid spelling mistakes and speed up development
• Syntax highlighting (colour coding text) - Can distinguish between different features quickly to check code is correct
• Auto Indent – Indents code automatically within structures to avoid errors

Question 7

What tools are provided by an IDE to debug software?

Answer 7

• Error highlighting - Syntax errors highlight dynamically so they can be corrected before running the program (saving time)
• Variable Watch window – Display the values of the variables during running of the program
• Break points- Stop the program at set points to check the values of variables. Developer can add multiple breakpoints.
• Error message list- Tells you where errors are and suggests corrections
• Stepping - Executes program one line at a time to watch variable values and program pathways
• Traces - Printouts of variable values for each statement execution

Question 8

What are the three programming constructs?

Answer 8

Sequence

Selection / Branching

Iteration

Question 9

What is an example of a count controlled loop?

Answer 9

FOR Loop - Will run for a set number of predetermined times.

Question 10

What is an example of a condition controlled loop?

Answer 10

WHILE / DO WHILE - Will run whilst a condition is true or false

Question 11

What are parameters?

Answer 11

Parameters are the variables listed between the brackets, after the procedure/function name e.g.

They become local variables in the routines that they are passed to.

characterMovement(inputKey, characterx, charactery)

Question 12

What does passing by value mean?

Answer 12

By Value (ByVal)
* Does not override the original data
* A local copy of the data is used
* Data is discarded when the subprogram exits

Question 13

What does passing by reference mean?

Answer 13

By Reference (ByRef)
* Changes are made to the original data
* Memory location of data is sent
* Changes remain after the subprogram exits
* Uses less memory

Question 14

What is a function?

Answer 14

• A named block of code which always returns a value
• Uses the keyword return
• Assigns the returned value to a variable (e.g. y)

Question 15

What is a procedure?

Answer 15

• A named block of code which does not return a value
• Does not use the keyword return
• Is called by writing its name but not assigning the result to a variable

Question 16

What is an OO class?

Answer 16

A template for defining methods and attributes, which is used to instantiate objects.

Question 17

What is an OO object?

Answer 17

An instance of a class which is created using a constructor (new)

Question 18

What is a OO Method?

Answer 18

These are the actions that can be performed by an object; for example, get a position on a game board. Can get a value (getter) or set a value (setter)

Question 19

What is an OO attribute?

Answer 19

Value held by object / link to variable

Each object will have its own public or private attributes.

Question 20

What is encapsulation?

Answer 20

• Attributes are set as private so they can only be accessed and changed via public methods
• Uses public ‘set methods’ to modify the value of a private attribute
• Uses public ‘get methods’ to retrieve the value of a private attribute
• Prevents unexpected changed to attributes having unforeseen consequences.

Question 21

What is inheritance?

Answer 21

• A child class has its own attributes and methods, but it also gets all attributes and methods from the parent class.
• When a method name is the same in a parent and child, then the method in the parent/super class will be overridden by the local version in the child.
• Uses the key word ‘inherits’ and ‘super’

Question 22

What is polymorphism?

Answer 22

• Code can be written that is able to handle different objects in the same way, this reduces the amount of code.
• Using methods with the same name in a subclass as in a parent class is called overriding, which is a type of polymorphism.
• Overriding allows a sub-class to use its own method rather than that of the parent.

Question 23

What would the constructor look like for the following class?

Answer 23

public procedure new(thePlayerID, thePosition,theMoney)
playerID = thePlayerID
boardPosition = thePosition
money = theMoney
endprocedure

Question 24

What would the pseudocode be to instantiate an instance of this class?

Answer 24

ObjectName = new ClassName (attributes required)

e.g. - Ronaldo = new Player(“Ronaldo”, 10, 1000000)

Question 25

What is recursion? Why does it need a stopping condition?

Answer 25

Recursion is the process of a subroutine calling itself from within itself
A stopping condition must be included which when met means that the routine will stop calling itself and will start to ‘unwind‘

No stopping condition would cause a ‘Stack Overflow’ error by filling the memory uncontrollably.

Question 26

What are the pros and cons of iterative algorithms?

Answer 26

• Has no limit to the number of times it may be called.
• Only one copy of the variable is required. This means that less memory will be used
• Uses a loop to repeat instructions. There is an end condition to the loop which decides when to stop looping
• Takes more lines of code and can be harder to understand

Question 27

What are the pros and cons of recursive algorithms?

Answer 27

• Too many calls may cause the program may run out of memory with a “Stack overflow” error
• Each call produces a new local variable which mean more memory spaces needed
• Uses a stopping condition in order to reach the end of the recursion
• Recursion calls itself whereas iteration does not.
• Uses less lines of code and produces a more elegant solution

Question 28

What would be the output if 10 was passed as a parameter into this function?

Answer 28

(1 + 2 + 3 + 6 + 7 + 10) = 29