Introduction to Programming

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Introduction to Programming

• Programming allows you to
• Issue commands to make the system do something
• Control how and when these commands are issued
• In general, each line in a program consists of a
  single command or control

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Lecture 7Colourful Programming

• Intro to VBA programming
• The programming environment
• Setting form properties
• Data types
• Variables
• Constants
• Example/ Tutorial
• HTML Hypertext Markup Language

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Control Constructs

• Sequence
• Each line of code is performed in sequence
• Selection
• At test of truth determines if one block of code
  or another is performed
• Iteration
• The same block of code is repeated whilst or
  until something is true

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Visual Basic for Applications

• A version of Visual Basic
• Most of the Microsoft Office applications have
  their own version of VBA
• The ability to generalise from VBA to VB
• Access VBA contains a large number of commands
  directly associated with the manipulation of
  Access databases

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Event-Driven Languages

• vs Procedural and Declarative
• Associated with events that may or may not occur
• Internally or externally determined
• User determines the order events occur
• This does not mean that procedural code is not
  written

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Object-Based Programming

• Everything, including the form itself, is an
  object
• Code is generally associated with an object and
  some event performed on it
• Each object can have one or more blocks of code
  associated with it depending on what you do with
  the object

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Design-Time

• Each of those objects has a set of properties
  associated with it that you can change
• Every time you create an object, it is
  independent of any other object
• Changes at design-time determines the state of
  those objects at run-time

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Object Properties
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Run-Time

• Each type of object has a pre-defined set of
  actions that the user can do to it
• Code may be written against any of them
• Each block of code associated with an event is
  called a Procedure
• The procedure will not be run unless that event
  occurs

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Code Window (1)
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Code Window (2)
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Background
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Environment (1)
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Environment (2)

• Private Sub Command0_Click()
• Form.RecordSelectors False
• Form.DividingLines False
• Form.NavigationButtons False
• Form.ScrollBars 0
• Form.Caption "Looking Good!"
• Command0.Left 5 567
• Command0.Top 1 567
• Command4.Left 5 567
• Command4.Top 3 567
• Command0.Caption ""
• Command4.SetFocus
• Command0.Enabled False
• Command4.Caption "Return"
• End Sub

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Environment (3)

• Private Sub Command4_Click()
• Form.RecordSelectors True
• Form.DividingLines True
• Form.NavigationButtons True
• Form.ScrollBars 3
• Form.Caption ""
• Command0.Left 1 567
• Command0.Top 2 567
• Command4.Left 9 567
• Command4.Top 2 567
• Command0.Enabled True
• Command0.Caption "Command0"
• Command4.Caption "Command4"
• End Sub

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Algorithm Design

• Probably the hardest part of programming
• What do you want the program to do?
• What objects do you need?
• Which event on what object?
• The steps within each procedure
• How objects interact with one another

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De-Bugging (1)

• There will always be errors!
• The most frustrating part of programming and
  takes the most time
• VBA is an Interpreted language
• Run it as soon as you write it
• Checked for Syntax as it runs
• Syntax rigidly applied
• Runs but doesnt do what you want
• Stops running

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De-Bugging (2)
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Text Entry (1)
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Text Entry (2)

• Private Sub Form_Load()
• Text1.Visible False
• Label6.Visible False
• Label7.Visible False
• End Sub

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Text Entry (3)

• Private Sub Command0_Click()
• Label6.Visible True
• Label7.Visible True
• Text1.Visible True
• Text1.SetFocus
• Text1.Text ""
• Text1.Text 2000 - Year(InputBox("Please enter
  your date of birth", "Date of Birth"))
• Command0.SetFocus
• End Sub

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Data Types

• String Text, including input from a TextBox,
  values displayed in a Label or values stored in
  the program between quotes
• Integer Whole numbers, for very large numbers you
  may need a Long
• Single Numbers containing decimal points, for
  large decimal numbers you may need a Double.
• Date Often useful if you are wanting to compare
  one date against another
• Variant As its name implies a Variant can vary
  and will take on the characteristics of whatever
  is passed to it. For example if an Integer value
  is passed to a variant it will act as though it
  is an Integer from that point

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Variables (1)

• In programming you often want to do something
  that requires the system to remember things
• Variables are areas set aside in the computers
  memory, for the duration of the program run
• You can assign values to variables
• As their name implies, the values they store are
  allowed to vary

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Variables (2)

• Each variable must have a unique name so that
  when the name is mentioned the system will know
  where to look
• The variable must be of a particular type
• To set aside an area of memory of a given type
  with a particular name, you need to declare it
  first

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Variables (3)

• Variables
• Syntax Dim name As data type
• e.g. Dim exam_result As Integer
• Constants
• Syntax Const name is assigned Value
• Const VAT 1.175

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Example
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Example

• Private Sub Command0_Click()
• Dim whole_number As Integer
• Dim big_whole_number As Long
• Dim decimal_number As Single
• Dim date_value As Date
• Dim can_be_anything As Variant
• whole_number 32767
• Text1.SetFocus
• Text1.Text whole_number
• big_whole_number 33333
• Text2.SetFocus
• Text2.Text big_whole_number

• decimal_number 32767 / 2
• Text3.SetFocus
• Text3.Text decimal_number
• date_value Date
• Text4.SetFocus
• Text4.Text date_value
• can_be_anything "This is text"
• Text5.SetFocus
• Text5.Text can_be_anything
• Command0.SetFocus
• End Sub

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Tutorial