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Chapter 1: VBasic
Variables, Operators, Conditional Statements, Combo/List Boxes
By Dirk Henkemans

Variables

Variables in visual basic can be declared anywhere in your program and are declared using the dim statement.

The syntax:

Dim X as Integer 'Creates an Integer Variable

Dim Name as String 'Creates a String Variable
There are several different kinds of common variables:

String
Your average text string. It can hold all letters and numbers.

Integer
Will hold any number from -256 to 256.

Long
Can hold numbers from -2,147,483,648 to 2,147,483,647.

Bool
The smallest variables. It can only store 1 and 0. These are normally used as true/false variables. 1 being true 0 being false.

Variable Scope

Variable scope is where in your program your variables can be seen. A variable declared in the declarations section (this coding section can be found by pulling down the left combo box of the coding form) has a global scope and can be accessed anywhere in your project.

While a variable that is declared inside your code, between the Sub and the End Sub, can only be accessed in that sub.

Operators

Operators are the things that make up the conditional part of the conditions statement. For instance in the code:

if text1 = "Yes" then

The operator would be the "=". I'm sure we are very familiar with the "=" operator.

Other operators are:

=       equals
<=      less then or equal to
<>      does not equal
=>      greater or equal too
* only the = and <> equal operators can be used with text.

Conditions

The syntax for the if statement is:
If [condition] then 
    [statement]
end if
For Example
If text1.text = "Programmers are lovable" then
        text2.text = "Programmers are very lovable"
End if
This Function would display "Programmers are very lovable" in text2 only if "Programmers are lovable" was displayed in Text 1.

A continuation of this is the elseif and else condition statements. They are used after an If statement. The syntax is:

If [first condition] then
        [code]
elseif [second condition] then
        [code]
elseif [third condition] then
        [code]
else    'does not need a condition because it is always triggered if
        'the other conditions are all not.
        [code]
end if
There may be as many elseif statements as needed but only one if and else statement per conditional group.

The Pirate Ship Program

This game is about 2 ships.

Add these controls to the form:
 
 




 










Now adjust the caption properties of the labels property so that they look like the following. Also for the sake of programming conventions adjust the text box names to match that of the caption beside it. Start the names for the user with "Y" and the opponents with "O". For example the last text box's name would be YHP.
 
 



Zipped Program


 






Now we start on the code.

The syntax for adding combo box items is:

[combo box].additem [item]

The code we are going to add into the form1 code is triggered by the form loading (appearing). In order to do this double click on the form and it will automatically go to "Load" event as that is the default event. Add the script:

Private Sub Form1_load()
'add the items for the different commands.
combo1.additem "Attack"
combo1.additem "Retreat"
combo1.additem "Flank"
Combo1.additem "Approach"
combo1.additem "Board"

'Enters the starting caption in the event label
label13.caption = "There is a ship attacking us.  What would you like do captain?"

'Starting values
YType.Text = "Barque"   'sets type
YArmour.Text = "25"     'sets armor
YCannon.Text = "20"     'number of cannon
YMen.Text = "100"       'men
YShots.Text = "500"     'shots
YHp.Text = "750"        'hp

'starting opponents values
OType = "Corvette"      'sets type
OArmour = "10"          'armor
OCannon = "25"          'cannon
OMen = "150"            'men
OShots = "750"          'shots
OHp = "750"             'hp

End sub
Now lastly we have to make the commands and add some AI (artificial intelligence). We do this with the command button: (oh just for those who think AI is mystical and magical, it is not. It is but a series of algorithms to base computer moves on certain conditions rather then any means of sentience.) If you notice while originally we had to add ".caption" to our labels and ".text" to access the properties of our labels and text boxes, this is not required for ONLY these properties as they default to caption or text if no property is given.
Private Sub Command1_Click()
If Combo1 = "Attack" Then
    If Distance >= 100 Then
        Label13 = "They are too far."
    ElseIf YPosition = 0 Then
        Label13 = "You are not in a attack position"
    ElseIf Distance < 100 Then
        OHP = OHP - 2 * YCannon + OArmour
        OMen = OMen - 0.5 * YCannon
        YShots = YShots - YCannon
        Label13 = "They have been hit."
        YPosition = 0
        Combo1 = "Flank"
    End If
    

ElseIf Combo1.Text = "Retreat" Then
    Label13 = "You are retreating."
    YPosition = 0

ElseIf Combo1.Text = "Flank" Then
    YPosition = 1
    Label13 = "We are now ready to attack them."
    Combo1.Text = "Attack"
    
ElseIf Combo1.Text = "Approach" Then
    YPosition = 1
    Distance = Distance - 20

ElseIf Combo1.Text = "Board" Then
    If Distance < 10 Then
        YMen = YMen - OMen
        If YMen > 0 Then
            Label13 = "You Win!!!"
        Else
            Label13 = "All your men where destroyed."
        End If
    Else
        Label13 = "You are too far away."
    End If
End If

'the & command adds the strings so that they form one
'long string
Form1.Caption = "(Distance =" & Distance & " )"

'The Events
If OHP < 0 Then
    Label13 = "Their ship is sunk."
ElseIf OMen < 0 Then
    Label13 = "You Win."
ElseIf YMen < 0 Then
    Label13 = "You loose."

'The AI
ElseIf Distance >= 100 Then
    Distance = Distance - 20

ElseIf OPosition = 0 Then
    OPosition = 1
    
Else
    YHP = YHP - 2 * OCannon + YArmour
    'the int command rounds the produced number to the nearest
    'integer
    YMen = Int(YMen - OCannon.Text * 0.5)
    OPosition = 0
    OShots = OShots - OCannon
 
End If

End Sub
We will do more on this project in the next chapter with random numbers, message boxes , & , and/or operator and form switching.

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