Internet Programming

1
Internet Programming

• Lecture 3

2
Web-based Forms and CGI Programs

• Forms are used to capture user input
• FrontPage simplifies their creation via Insert
  Form
• To a blank form you can insert
• Text, Tables, Graphics
• Check Boxes, Push Buttons, Radio Buttons
• Drop Down Menus

3
Processing a Form

• To process the data captured on a form you can
• Submit the form to a remote CGI (Common Gateway
  Interface) program
• Write a program (or script) using a simple
  scripting language such as JavaScript or VBScript

4
Programming Languages

• Need to be structured language.
• Three basic language structures
• Sequence
• Selection
• Iteration

5
Sequence

• A list of actions to be carried out in the order
  specified
• Do this
• Now do this
• Then this
• Finishing with this.

6
Selection

• Choose from one or more options which action to
  take
• If you want to do this Then Do it
• Else Do this instead
• End If

7
Multiple Selection

• If selectnum 0 Then exit
• ElseIf selectnum 1 Then DoCmd WCLUPD.Show
• ElseIf selectnum 2 Then DoCmd WENQ.Show
• ElseIf selectnum 3 Then DoCmd WCOMDUE.Show
• Else MsgBox You MUST type 0,1,2 or 3
• End If
• End If
• End If
• End If

8
Multiple Selection 2

• Cumbersome using nested IfThenElses
• Select Case selectnum
• Case 0 exit
• Case 1 client enquiry and input/changes
• DoCmd WCLUPD.Show
• Case 2 enqiry screen and reports
• DoCmd WENQ.Show
• Case 3 commission due to introducers
• DoCmd WCOMDUE.Show
• Case Else
• MsgBox You MUST type 0,1,2 or 3
• End Select

9
Iteration (Loops)

• Some tasks have to be repeated
• e.g. delegate details are added one delegate at a
  time until all have been booked on a course.
• Or each record in a database has to be examined
  to see if it meets some given criteria

10
Loop Constructs

• The For . Next
• There are two variants of this structure
• For counterstart To end Step step
• Exit For
• Next
• Which executes the loop once for each value in a
  series that begins with start and ends with end
  and increments by step.

11
Another For Loop

• The second form is
• For Each element In group
• Exit For
• Next
• Which executes the loop for each element in a
  collection or array.
•  

12
Yet More Loops

• b) Do While/Until condition
• Exit Do
• Loop
• c) Do
• Exit Do
• Loop While/Until condition
• d) While condition
• Wend

13
An Example

• WHILE NOT Rs.EOF
• Count Count 1
• Response.Write("ltligt")
• Response.Write("lth4gt")
• Response.Write("lta href'photos.asp?Counter")
• Response.Write(Count)
• Response.Write("'gt")
• Response.Write(Rs("title"))
• Response.Write("lt/agt")
• Response.Write("lt/h4gt")
• Response.Write("lt/ligt")
• Rs.MoveNext
• WEND

14
End of lecture 3