Mark Dixon, SoCCE SOFT 131Page 1 07 – Iterative Execution

Mark Dixon, SoCCE SOFT 131Page 2 Coursework 1 (Test) - Results Student Number Score (max 50) Classification is for guidance only Please feel free to come and discuss your results with me

Mark Dixon, SoCCE SOFT 131Page 3 Coursework 1 (Test) - Debrief Range of marks normal Failure rate quite high – 30% (3 / 10) –not unusual for this module –recoverable if corrective action is taken Please feel free to discuss marks in tutorial

Mark Dixon, SoCCE SOFT 131Page 4 Coursework 1 (Test) - Problems Answer question: –Name a variable: Dim x  x Conditional expressions: x > 4 –used in conditional statements: If picMain.height < 0 Then Parameters – data given to functions: x = Int(34.56) sqr(b)

Mark Dixon, SoCCE SOFT 131Page 5 Session Aims & Objectives Aims –To introduce the main concepts involved in getting the machine to perform repetitive tasks. Objectives, by end of this week’s sessions, you should be able to: –To be able to implement code that does repetitive tasks, using looping structures: known limits (for loop) unknown limits (do loop)

Mark Dixon, SoCCE SOFT 131Page 6 Example: Hello v0 Hello Option Explicit Sub btnHello_OnClick() lblHello.innerHTML = lblHello.innerHTML & "Hello " End Sub 1 user click: 1 Hello (1 line of code)

Mark Dixon, SoCCE SOFT 131Page 7 Example: Hello v1 Option Explicit Sub btnHello_OnClick() lblHello.innerHTML = lblHello.innerHTML & "Hello " End Sub 1 user click: 10 Hellos (10 lines of code) Lots of lines imagine 300 Hellos

Mark Dixon, SoCCE SOFT 131Page 8 Example: Hello v2 Option Explicit Sub btnHello_OnClick() Dim h For h = 1 to 10 lblHello.innerHTML = lblHello.innerHTML & "Hello " Next End Sub 1 user click: 10 Hellos (4 lines of code)

Mark Dixon, SoCCE SOFT 131Page 9 For... Next statement repeat code known number of times –reduces length of code –easier to change Syntax: For variable = start To end statementblock Next

Mark Dixon, SoCCE SOFT 131Page 10 Advantages Less code: This makes program: –Easier to read –Easier to change (imagine 500 Hellos) Option Explicit Sub btnGo_OnClick() Dim h For h = 1 To 10 lblHello.innerHTML = lblHello.innerHTML & "Hello " Next End Sub Option Explicit Sub btnGo_OnClick() lblHello.innerHTML = lblHello.innerHTML & "Hello " End Sub Hello v1Hello v2 10 lines 4 lines

Mark Dixon, SoCCE SOFT 131Page 11 Real Power of loops –using counter variable –do something slightly different each time Example: Dim num Dim tot tot = 0 For num = 1 To 5 tot = tot + num Next lblRes.InnerText = tot Example: Total

Mark Dixon, SoCCE SOFT 131Page 12 Example: Total

Mark Dixon, SoCCE SOFT 131Page 13 Question: For … Next What does the following code produce: Dim counter For counter = 1 To 10 lblNums.InnerText = lblNums.InnerText & counter Next What does the following code produce: Dim i For i = 24 To 8 Step -2 lblNums.InnerText = lblNums.InnerText & i & i * 2 Next

Mark Dixon, SoCCE SOFT 131Page 14 Example: Letter Count Option Explicit Sub btnCount_OnClick() Dim pos Dim count Dim char count = 0 For pos = 1 To Len(txtWords.value) char = Mid(txtWords.value, pos, 1) If char = "e" Then count = count + 1 End If Next lblCount.innerText = count End Sub

Mark Dixon, SoCCE SOFT 131Page 15 Example: Shades Option Explicit Sub btnShow_OnClick() Const stTag = "<span style=""background: #" Dim h, p, msg, red msg = txtMsg.value h = "" red = 255 For p = 1 To Len(msg) h = h + stTag + Hex(red) + "0000"">" h = h + Mid(msg, p, 1) h = h + " " red = red - 5 Next divTones.innerHTML = h End Sub

Mark Dixon, SoCCE SOFT 131Page 16 Do... Loop statement repeat code unknown number of times –more flexible than For –slower than For Syntax: Do [{While|Until} condition] [statementblock] Loop

Mark Dixon, SoCCE SOFT 131Page 17 Example: Do … Loop Can do everything a For … Loop can: Dim IDim i i = 1 Do While i <= 10For i = 1 To 10 lblN.InnerText = i picN.InnerText = i i = i + 1 LoopNext And more: Dim i i = 1 Do While i < 10 lblN.innertext = i If (i / 2) = Int(i / 2) then i = i + 1 Else i = i + 3 End If Loop

Mark Dixon, SoCCE SOFT 131Page 18 Question: Do … Loop What does the following produce: Dim num num = 20 Do While num > -12 lblDo.InnerText = lblDo.InnerText & num num = num Loop What does the following produce: Dim num num = 6 Do Until num > 4 num = num + 5 lblDo.InnerText = lblDo.InnerText & num Loop

Mark Dixon, SoCCE SOFT 131Page 19 Tutorial Exercise: Hello Task 1: Get the Hello Example (from the lecture) working. Task 2: Modify your page so that it uses a variable to temporarily build to html. Task 3: Modify your page so that the user can control how many 'Hellos' appear.

Mark Dixon, SoCCE SOFT 131Page 20 Tutorial Exercise: Letter Count Task 1: Get the Letter Count Example (from the lecture) working. Task 2: Modify your Letter Count page, so that the user can control which letter is counted. Hint: You will need a text box for the user to type a letter into. Task 3: Modify your Letter Count program, so that the user cannot type more than one letter in the letter text box. Hint: Use the text box’s change event, and the len function.

Mark Dixon, SoCCE SOFT 131Page 21 Tutorial Exercise: Vowel Count Task 1: Create a new page that counts the number of vowels (a, e, i, o, u) in a piece of text. Hint: similar to the letter count example.

Mark Dixon, SoCCE SOFT 131Page 22 Tutorial Exercise: Shades Task 1: Get the shades example from the lecture working. Task 2: Modify the page so that it puts a space in between each letter. Task 3: Change the program so that it uses shades of another colour instead. Task 4: Create a new page that selects random shades of your selected colour. Hint: use the Rnd function.

Mark Dixon, SoCCE SOFT 131Page 23 Tutorial Exercise: Chess Board Task 1: Use one for loop inside another to create a chess board.