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From: vittal <vittal...@yahoo.co.in>
Date: Feb 22, 2006 11:50 AM
Subject: VB1
To: Vittal P <vittal...@gmail.com>

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 LESSON 1 -- Getting started

 Defining basic terms ApplicationAn application is a collection of objects
that work together to accomplish something useful. In VB the application is
called a *Project*. A Project could be a the management of a Video store,
the calculation of mortgages, a dating service or the Payroll for 1000
employees.
ObjectAn object is a piece of software that has properties and functions
that can be manipulated. Whew! You're here so, you must be somewhat familiar
with the Windows environment. A window is an *object*. It has *properties*:
size, color, position on the screen, etc. (The purists among you may want to
talk about a* class* rather than an *object* but, at this point we just want
to keep it simple, and the underlying concept is the same). The window has
functions, also called *methods*, that can be manipulated: change the size,
move it around, open it and close it. You do not have to write code to
resize a window - you just click and drag. But somebody had to write code at
some point. Fortunately for us, when they did they put it all in a nice
little package and called it a *window object*. Now, whenever you need a
window in your Project you can make a copy of the window object, change its
properties for color or size very easily, and paste it where you want it.
Then you can use its built-in methods to open it, close it when you want or
resize it whenever necessary. When you create an application using objects
and combining them to produce results, you are working in an *
object-oriented* environment.

Event-drivenTo produce an application in COBOL, a procedural language, you
write COBOL source programs, you compile them into machine code and then you
run them via a control interface such as JCL. A program can contain 1000's
of lines of source code and could run for hours with no human intervention.
In fact, in large installations, a jobstream can consist of a dozen
programs, all automatically accepting input from the previous program and
producing output for the next. The programmer can be blissfully unaware that
the program has run unless something catastrophic happens.

In a VB project, the processes that occur have to be associated with *events
*. An event is something that happens - the user clicks on a button, a form
is opened, the result of a calculation is too large. The operation is *
event-driven* because everything that executes does so as the result of some
kind of event. The role of the programmer is to anticipate the events and to
write the code that will be executed when the event occurs. A VB application
is *interactive* in the sense that the user is constantly interacting with
the program. The user inputs a Customer Id, the program checks the Id in the
database and immediately brings up the customer's file or displays a message
that the particular Id is invalid.

Top <http://www.profsr.com/vb/vbless01.htm#Start>

Jumping right in! Project descriptionWe want to create a Scoreboard for a
football game (there it is already!) between the Giants and the Redskins. To
begin with the simplest task we will only count the touchdowns and display
appropriate messages.

*Please note*: although we will create a complete functional Project with
controls and code and so on, the purpose of this exercise is to show what
can be done. In the following lessons we will be explaining scripts and the
use of controls in a lot more detail. If you study this example you should
be able to relate it to what you already know of programming and judge
whether this tutorial will be easy or hard for you to do.

Creating the ProjectFirst thing to do is to create a Directory where you
will store all your VB Projects. Call it VBApps, for example. Then start VB.
The first screen will ask whether you want to open a new project or an
existing one - it's obviously a new one and it will be a Standard EXE. Then,
maximize all the windows (it's easier to work with - some of the examples in
the tutorial had to be reduced for the sake of the presentation). Now, save
your project. It will first ask you to save the form - call it Score.frm -
and then the Project - call it Scorebrd.vbp. From now on, do File-->Save
Project very, very frequently.

Before you start to build-up the form, it will make it easier if you change
the color of the form. Otherwise you will be working with grey controls on a
grey background. To change the color, just click anywhere on the form, go to
the properties window, find the property called BackColor and change it to
the standard Window background (teal) or to any color you want in the
palette.

In our first example we will need 6 *labels* and 2 *command buttons*. Each
one of these objects that you put on a Form is called a* control*. To get a
control you go to the *Toolbox*, click on the control you want, come back to
the Form and click and drag the control to the size and position you want.
Position the controls somewhat like in the diagram below.

*IMPORTANT NOTE*: If this is your first experience with VB, don't be afraid
to experiment. This is hands-on stuff! Remember that VB is a Microsoft
product, therefore it works with the standard Windows interface. All the
functions you know from MS-Office work the same way here: Copy, Cut, Paste,
(Ctrl)+(Click), (Shift)+(Click), drag the mouse over a group of controls to
select them all, etc. The Undo button is a nice one to keep handy - when you
modify a control you can always Undo the change - remember this when you get
to the part about aligning the controls, making them all the same size and
so on. That part can get tricky. If you accidentally end up in the Code
window while palying around, go down a few paragraphs and you will see how
to get back to the Form. At this point the worst that can happen is that
your Form will get all messed up. *So what!* You can just scrap it and start
over again, but you will have learned something.

Now that we have a bunch of controls on the form, we have to jazz them up a
bit. We do this by changing the *Properties* of the controls in the *Properties
window*. Each control has a whole series of properties, most of which we
won't need right now. The ones we do need are:
Alignment = how text aligns in the control
BackColor = choose the color of the background
Caption = the text that will appear in the control
Font = choose the font type and size
ForeColor = choose the color of the text (foreground)

As with all Windows applications, you can select multiple controls with
(Ctrl)+(Click) and change a property for all of them at once. For example,
if all backgrounds are white, select all controls, change ForeColor to white
and all of them are modified. Change your form to look like the one below.
Note that you do not have to change the Caption for Label4, Label5 and
Label6 and that you can't change the color of the buttons. They insist on
being what was called in the old days "IBM grey". *Don't forget to save your
project often as you go along!*

If you *Run* the application at this point, you should see your Form appear,
just the way you created it. However if you click on any of the
controls, *absolutely
nothing happens!* There are *events* that occur; the form opens, a button is
clicked, etc. But, there is nothing that tells the form what to do when it
sees an event. That is why we have to write code, also called *script*.

Top <http://www.profsr.com/vb/vbless01.htm#Start>

To switch between the Code window and the Form window, use the buttons just
over the Project Explorer window (diagram on the left).
Once in the Code window, you have the option of seeing all the code for the
Project or the code for one event at a time. Use the buttons in the lower
left-hand corner (diagram on the right).
To select the object and the event you wish to code, use the two Listboxes
at the top of the Code window. The one on the left for the object and the
one on the right for the event. Start with *General ... Declarations* and
then *Form ... Load*, etc.

Now we can *Run* it and see something happen. When the Form loads, it will
initialize the fields that we specified in the code.

Now code the Command1 button and Run it to see the result.

Assignment 1Using what you learned when coding the Command1 button, write
the code for the Command2 button so that the score for the Redskins can also
be captured. *Hint*: don't hesitate to use Copy and Paste.

After you've done it, check out the
Solution<http://www.profsr.com/vb/vbasgn1.htm>.

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