A-level Computing 2009/AQA/Problem Solving, Programming, Data Representation and Practical Exercise/Skeleton code/2011 Exam/Section C

Discussion of the code Potential questions Validation List the Erroneous, Extreme and Typical Data for a user selecting a menu item: A:   In the exam you might be asked to give only one example of each Test Type Test Data Typical 3 Extreme 1,4,9 Erroneous 10, -7, 5, 6   List the Erroneous, Extreme and Typical Data for a manual bowling die: A:   In the exam you might be asked to give only one example of each Test Type Test Data Typical 3 Extreme 1,6 Erroneous 0, 9, -45   List the Erroneous, Extreme and Typical Data for a manual appeal die: A:   In the exam you might be asked to give only one example of each Test Type Test Data Typical 3 Extreme 1,4 Erroneous 0, 5, 78   Variables Give the name of the identifier of a Constant A:       MaxSize   Give the name of the identifier of a global variable A:       MaxSize (even though this is a constant, it can still be counted as a variable and is the only global declaration)   Give the identifier of a local variable A:   you would only have to list one in the exam if asked this question     PlayerOneName, PlayerTwoName, OptionSelected, Count, PlayerName, OptionChosen, BowlDieResult, RunsScored, AppealDieResult, LowestCurrentTopScore, PositionOfLowestCurrentTopScore, Count (there are multiple of these), Count2, LineFromFile, PlayerOut, CurrentPlayerScore, AppealDieResult, PlayerNo, PlayerOneScore, PlayerTwoScore, BowlDieResult, RunsScored   Note the identifier of an array: A:       ValuesOnLine(2), TopScores(MaxSize)   Give the identifier of a user defined data type: A:   you might be asked to explain more about this, so revise structures (records)     TTopScore   Give an example of an assignment statement: A:   remember, assignments are where you give a variable a value     PlayerOneName = GetValidPlayerName(), TopScores(Count).Score = 0   Give an example of a variable declaration: A:   there are dozens of these...     Dim Count As Integer   Why might we not want to store an average score as an integer? A:       An integer would not be suitable as an average score may include decimal values.   Loops Give the name of a stepper variable used in a loop? A:       Count in the ResetTopScores procedure   Give the name of a fixed variable used in a loop? A:       MaxSize in the ResetTopScores procedure - But MaxSize is a constant not a variable! It can still be classed as a variable.   Give the name of a follower used in a loop? A:       ???   Give the name of a most recent holder used in a loop? A:       RunsScored in PlayDiceGame and LineFromFile in LoadTopScores   Sub Routines Write down a function declaration used in the program A:       Function GetValidPlayerName() As String   Write down a function call used in the program A:       PlayerOneName = GetValidPlayerName() ; PlayerTwoName = GetValidPlayerName() ; BowlDieResult = RollBowlDie(VirtualDiceGame) ; AppealDieResult = RollAppealDie(VirtualDiceGame). Make sure that you include the = as a function call will always return a value   Write down a procedure declaration used in the program A:       Sub ResetTopScores(ByRef TopScores() As TTopScore)   Give the name of a parameter used in a procedure A:       VirtualDiceGame, BowlDieResult, RunsScored, CurrentPlayerScore, etc.   Explain the difference between using byRef and byVal A:       byRef refers to the original value that is passed to the sub routine, and any changes made to the value inside the subroutine are applied directly to the original value as well, byVal copies the value into another variable inside the subroutine and any changes made to this value are not made to the original   Why is Byref used in the ResetTopScores sub routine? A:       the routine wants to reset the Top Scores, as the top scores are not a global variable we use byRef to refer to the original value and any changes made to TopScores are made directly to the TopScores array   Write down where a return value for a function is assigned: A:       GetValidPlayerName = PlayerName, RollBowlDie = BowlDieResult, CalculateRunsScored = RunsScored   Trace Tables Construct a trace table for the ResetTopScores procedure when passed the following data: Maxsize Count TopScores 1 2 3 4 name score name score name score name score 4 Peter 23 Michael 65 Aubrey 24 Marea 89   A:       Maxsize Count TopScores 1 2 3 4 name score name score name score name score 4 Peter 23 Michael 65 Aubrey 24 Marea 89 4 1 - 0 4 2 - 0 4 3 - 0 4 4 - 0