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07 – Arrays, & Constants

07 – Arrays, & Constants. In-class Test Results. Score (max 25). Student Number. Session Aims & Objectives. Aims To introduce the main concepts involved in handling more complex (multi valued) data Objectives, by end of this week’s sessions, you should be able to:

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07 – Arrays, & Constants

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  1. 07 – Arrays, & Constants

  2. In-class Test Results Score (max 25) StudentNumber

  3. Session Aims & Objectives • Aims • To introduce the main concepts involved in handling more complex (multi valued) data • Objectives,by end of this week’s sessions, you should be able to: • declare, assign values to, and use: • constants, and • arrays,

  4. Example: German Numbers • SPECIFICATION • User Requirements • help people learn German numbers 1 - 10 • Software Requirements • Functional: • store text of German numbers 1-10 • select one at random • present text to user • user enter digits • Non-functionalshould be easy to use • User Requirements • describe user's objectivesno mention of technology • Software Requirements • Functional • list facilities to be provided (often numbered) • Non-functional • list desired characteristics(often more subjective)

  5. Array Variables (what) • multiple values – stored in single variable • index – identifies individual values (called elements) • the value of element 3 is 155

  6. Array Variables (how) • Declaration:Dimvarname(last)e.g. Dim HR(16) Dim x(8) • Assignment:arrayname(index)=valuee.g.HR(0) = 134 HR(5) = 151 x(5) = 23.87 x(7) = 189.2516

  7. Arrays Animation

  8. Arrays: why? (declaration) 5 variable declarations Single array declaration Dim Name1 Dim Name2 Dim Name3 Dim Name4 Dim Name5 Name1 = “Bob” Name2 = “Sally” Name3 = “Jo” Name4 = “Fred” Name5 = “Alison” Dim Name(4) Name(0) = “Bob” Name(1) = “Sally” Name(2) = “Jo” Name(3) = “Fred” Name(4) = “Alison”

  9. Arrays: why? (use) Dim Num Num = 2 If Num = 1 Then Res = Name1 ElseIf Num = 2 Then Res = Name2 ElseIf Num = 3 Then Res = Name3 ElseIf Num = 4 Then Res = Name4 Else Res = Name5 End If Dim Num Num = 2 Res = Name(Num) Single line of code picks any element

  10. Example: German Numbers Array Declaration Array Assignment Array Use <html> <head> <title>German Numbers</title> <script language=vbscript> Option Explicit Dim Nums(10) Dim Num Sub Window_OnLoad() Nums(1) = "eins" Nums(2) = "zwei" Nums(3) = "drei" Nums(4) = "vier" Nums(5) = "funf" Nums(6) = "sechs" Nums(7) = "sieben" Nums(8) = "acht" Nums(9) = "neun" Nums(10) = "zehn" Randomize End Sub Sub btnStart_OnClick() Num = 1 + CInt(Rnd() * 9) lblQuest.innerText = "What is " & Nums(Num) & "?" End Sub </script> </head> <body> <p ID=lblQuest> <p><input type=button id=btnStart value=Start> <input type=text id=txtNum> <input type=button id=btnCheck value=Check> </body> </html>

  11. Questions: Arrays • Write a line of code that declares an array called Books with 56 elements • Write a line of code that assigns to value 45 to the 18th element of the array. • Write some code that makes the background red, but only when the 12th array element is larger than 6 Dim Books(56) Books(18) = 45 If Books(12) >6 Thendocument.bgcolor = "red" End If

  12. Example: Capital Cities <html> <head> <title>Caplital Cities</title> <script language=vbscript> Option Explicit Dim Country(4) Dim City(4) Dim Num Sub Window_OnLoad() Country(1) = "UK" City(1) = "London" Country(2) = "France" City(2) = "Paris" Country(3) = "Spain" City(3) = "Madrid" Country(4) = "Greece" City(4) = "Athens" Randomize End Sub Sub btnStart_OnClick() Num = 1 + CInt(Rnd() * 3) lblQuest.innerText = "What is the capital of " & Country(Num) & "?" End Sub </script> </head> <body> <p ID=lblQuest>Please press Start button to begin. <p><input type=button id=btnStart value=Start> <input type=text id=txtNum> <input type=button id=btnCheck value=Check> </body> </html>

  13. Script Debugging • Labs have script debugging disabled • Tools menu • Internet Options • Advanced tab • Disable ScriptDebugging

  14. Error: Subscript Out of Range • Index too big/small <HTML> <HEAD> <TITLE></TITLE> <script language=vbscript> Option Explicit Dim x(3) x(0) = 9 x(1) = 5 x(2) = 21 x(3) = 23 x(4) = 12 </script> </HEAD> <BODY> </BODY> </HTML>

  15. Constants • similar to variable • value given in declaration • however value can’t be changed • useful for removing'magic numbers' • declaration syntax: • name used to represent literal value Constconstantname=expression

  16. Constants: Example Option Explicit Dim Nums(10) Dim Num Sub Window_OnLoad() Nums(1) = "eins" Nums(2) = "zwei" Nums(3) = "drei" Nums(4) = "vier" Nums(5) = "funf" Nums(6) = "sechs" Nums(7) = "sieben" Nums(8) = "acht" Nums(9) = "neun" Nums(10) = "zehn" Randomize End Sub Sub btnStart_OnClick() Num = 1 + CInt(Rnd() * 9) lblQuest.innerText = "What is " & Nums(Num) & "?" End Sub • Some numbersrepresent thesame thing • e.g. the last elementof the array • changes • take time • could make mistake

  17. Constants: Example Declaration ofConstant Use ofConstant Option Explicit Const Last = 10 Dim Nums(Last) Dim Num Sub Window_OnLoad() Nums(1) = "eins" Nums(2) = "zwei" Nums(3) = "drei" Nums(4) = "vier" Nums(5) = "funf" Nums(6) = "sechs" Nums(7) = "sieben" Nums(8) = "acht" Nums(9) = "neun" Nums(10) = "zehn" Randomize End Sub Sub btnStart_OnClick() Num = 1 + CInt(Rnd() * (Last - 1)) lblQuest.innerText = "What is " & Nums(Num) & "?" End Sub • replaceliteral numbers • with constant • name representsvalue • only need to changeconstant

  18. Error: Illegal assignment <HTML> <HEAD> <TITLE></TITLE> <script language=vbscript> Const hi=4 Dim x(hi) x(1) = 5 x(2) = 12 x(3) = 9 hi=6 </script> </HEAD> <BODY> </BODY> </HTML>

  19. Questions: Arrays • Write a line of code that declares a constant called MaxGoes with a value of 3 • Write some code that makes the background red, but only when a variable called Goes is larger than MaxGoes Const MaxGoes = 3 If Goes > MaxGoes Then document.bgcolor = "red" End If

  20. Tutorial Exercise: German Numbers • Task 1: Complete German Numbers Example from lecture, using constants.You will need to complete the code for checking the user's answer • Task 2: Modify your page so that it hides and shows the buttons appropriately • Task 3: Modify your page so that it plays appropriate sounds when the user gets the answer right/wrong • Task 4: Modify your page to allow the user 3 attempts only.

  21. Tutorial Exercise: Capital Cities • Task 1: Complete Capital Cities Example from the lecture, adding some more cities, and using constants.You will need to complete the code for checking the user's answer • Task 2: Modify your page so that it hides and shows the buttons appropriately • Task 3: Modify your page so that it plays appropriate sounds when the user gets the answer right/wrong • Task 4: Modify your page to allow the user 3 attempts only. • Task 5: Modify your page so that it is case in-sensitive (i.e. user can type upper or lower case)

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