Re: Jim's VB.Net Notes: Intro And Lesson 01
- From: "RicksPlace" <ofbgmail@xxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Thu, 22 Jul 2010 18:13:49 -0400
Nicely Done Jim.You have a flare for technical writing.
It was clear, concise and enjoyable to read through.
Rick USA
----- Original Message -----
From: Homme, James
To: programmingblind@xxxxxxxxxxxxx
Sent: Thursday, July 22, 2010 3:00 PM
Subject: Jim's VB.Net Notes: Intro And Lesson 01
Jim's Vb.net Notes
By Jim Homme
----------
Introduction
This is my brain dump to you as I learn Visual Basic .Net. I hope it helps
you.
I found, when I was learning my first programming language, Cobol, that if I
wrote the concepts down as I learned them, they stuck better. Whatever your
learning style, I hope you get something out of these notes.
----------
The Approach
The approach I will take is going to be simple. I'm going to try to
intentionally use short examples that teach a concept at a time. Along the way,
I will try to pull a few examples together that demonstrate several concepts
that we've recently gone over.
We will repeat concepts as we move through the notes, but when we do that,
with each successive treatment, we will dive deeper into the concepts we repeat.
----------
Programming Environment
As our programming environment we'll use a text editor called EdSharp, from
Jamal Mazrui. So go get it from http://www.empowermentzone.com/edsetup.exe.
Install it. Get familiar with it. Switch to the compiler setting for Visual
Basic .Net. Then make a directory for programs. Come back here when that's done
and let's get going.
----------
Adding A Compiler Setting For Visual Basic Console Applications
We'll write some console applications at the beginning of the tutorial to
cut down on and focus the learning curve. In order to get them to compile
properly, we need to set up a line in the EdSharp main.ini file that will
compile console applications. That's going to be extremely easy as long as you
carefully follow these next instructions.
Open EdSharp.
Press Alt + Shift + M. This opens the main.ini file.
Press Control + F and search for the string visual basic .net. The cursor
will land on a line that contains the command line string EdSharp uses to
compile a windows executable Visual Basic .Net program.
Put the cursor on the beginning of that line and press F8 to start a
selection block.
Scroll down until you've selected the entire compiler directive and move one
character past it.
Press Shift + F8. EdSharp selects the whole compiler directive.
Press Control + C to copy the text to the clipboard.
Create a blank line and paste with Control + V.
Change the beginning of the line to read something like Visual Basic .net
Console Application, so that you know what it does when you pick it from the
list of compilers.
Carefully move the cursor over to a string that reads in part winexe.
Delete the win from that string.
Save the file with Control + S.
You now will be able to compile Visual Basic .net Console applications in
EdSharp and you're ready for the first few lessons.
----------
Lesson 01: As Tradition Would Have It
Programmers are steeped in tradition. I'm not about to break tradition, so
our first program will be the HelloWorld program. It simply prints the words
"Hello world!" in quotes to the screen. I'll explain what's going on after the
program.
Let's get set up. For this lesson, and until I tell you to, use the console
application compiler setting you created in the introduction to this tutorial.
Probably the easiest thing to do is to put this tutorial file in the folder
where you have your programs and make it a favorite in EdSharp. That way, you
can make bookmarks in it and you don't have to go through the File Open dialog
to select a text file to open it.
For every program after this one, try to type it into EdSharp. Don't paste.
But do paste this one, because I want you to get used to compiling a program
and running it without the headache of compiler errors to deal with.
In the future, I want you to type all programs in. If you type them in,
you'll get used to seeing compiler errors. Compiler errors are messages the
compiler puts on the screen when it doesn't understand something you put in
your program.
Once you've pasted the program, save it. Then compile it. Then go to the
command line and run it. To do that, type it's name without an extension. It
will print the words Hello world to the screen and wait for you to press Enter.
So for every program you write, you're going to do three things.
1. Write some code.
2. Save it.
3. Run it.
Ready? Here we go.
----------
Let's Do It: Program 01, HelloWorld.vb
Paste the below program into a separate window and save it.
' HelloWorld.vb
' Print a message to the screen.
' Wait for the user to press Enter
' Exit
imports system
Module HelloWorld
Public Sub Main()
Console.WriteLine("Hello, world!")
Console.ReadLine()
End Sub
End Module
----------
What Did We Just Do: Program 01, HelloWorld.vb
There was a lot going on in that little program. As of this writing, I don't
know everything that happened, but here's what I know.
----------
Comments
Those lines at the top of the program that start with single quotes are
called comments. They give you a way to make notes to whoever is reading your
code. The compiler ignores them.
----------
The Line That Starts With Imports
This instructs the compiler to include a whole bunch of stuff from .Net. I
included this line, because I tried the program on two computers. It wouldn't
run on one computer without it.
----------
Code Blocks
In Visual Basic.Net, and any other language pretty much, we write programs in
chunks of code called code blocks. It's easy to tell in Visual Basic.Net where
a code block starts and ends. At the beginning of a code block will be a line
that starts with a keyword. At the end of the code block will be the word end
followed by that same keyword.
Our HelloWorld.vb program has two code blocks. One starts with Module and
ends with End Module. The other starts with Sub and ends with End Sub.
Module/End Module
From what I understand at this point in my learning, every Visual Basic.net
program must have at least either one class or one module, and the line at the
top and bottom of this program satisfies that requirement.
----------
Sub Main/End Sub
From what I know right now, any program that uses .Net must have a routine
whose name is main. This program satisfies that requirement.
----------
Console.WriteLine and Console.ReadLine
Here's what I know about these two lines.
The Console.WriteLine and Console.Readline statements are there to run
something called methods. Methods usually act on data in some way. The second
line is just there to make the program pause while you examine the line on the
screen that says "Hello world!" You'd normally use it to get data from someone
at the console who is using a keyboard to type stuff for your program to do
something with.
The Console.ReadLine method gets data, puts something onto the end of it that
makes your console take a new line, and sends all of that to the screen.
----------
Sub/End Sub
The word right before main in the program tells Visual Basic that we're
starting something called a subroutine. A subroutine is another kind of code
block you can call to make it do stuff with data if you want to. Later on in
the tutorial, I'll have more to say about the differences between subroutines
and methods.
----------
Our Program's Relationship To .Net
The Imports System at the top of the program tells the compiler to bring in a
whole bunch of stuff in a thing called a name space. The name space is called
System. We're using something in the System name space called Console. Console
is a class. The Console class contains methods. We used two of them.
----------
Lesson 01 Conclusion
As I said in the introduction to this tutorial, we are going to repeat a lot
of concepts, but go more deeply into them each time we do, so try to put aside
your curiosity about any questions you may have about the things we've just
barely touched on and get a feel for running the program and think about how
it's interacting with the system console.
Lesson 01 Lab: Your Turn
Copy the program to a new name and make sure the file name ends in .vb.
Change the stuff at the top of the program after the single quotes. Compile it.
Did anything change?
Go down inside the main subroutine and change the stuff inside the quotes.
Recompile and run the program. What happened this time?
Purposely introduce a misspelling in one of the lines and try to recompile.
What happened?
See you in the next lesson!
Jim
Jim Homme,
Usability Services,
Phone: 412-544-1810. Skype: jim.homme
Internal recipients, Read my accessibility blog. Discuss accessibility here.
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