One of the most exciting new possibilities that a developer has in Visual Basic .NET is the capability of spawning different threads with Visual Basic. Now this was only possible in previous versions of Visual Basic by digging down into the win 32 API, and it was just a very involved process and it wasn't very efficient or very easy. But this has been made very, very easy in .NET. And I am going to show you just an example. Let's talk about first of all what is a thread? What's the big deal with threading? Well a thread is a smallest executable section of code that's being processed; now this is a small chunk of your program that is being sent to the processor, this is the smallest section that the processor is handling at any one time. So let's think of it this way, think of it as a single line of code. Now whether or not this is exactly the correct terminology to use, it's what we are going to use here just to try to graphically show you what threading is and what's the big deal. Now picture your processor, this blue thing is your processor and you've got some code. We've got two pieces of code here. Now what we want to imagine is, in a normal situation only one of these chunks of code can run at one time. For example this particular line right here, this is one line, would be handed down to the processor. And then in a normal situation or a non-threaded situation, we would wait for this one to run and then this one would run OK, and we would go all the way through these. And once this particular program was finished, then this particular program could begin to run and the processor would make people wait in line. Because we only had one thread executing. But now with Visual Basic .NET, what will happen is this particular line can begin to execute and then we can spawn a new thread. And the new thread to get spawned can send information down to the processor, and the processor would then begin to switch. It will run this thread, and then it will switch and run this thread; when it is ready for more it will go back and grab another line here and execute this on this thread and then switch and grab more over here and run this. And so what we have are these two programs running and they look to us as if they are running simultaneously; now actually the processor is only executing a single thread at a time. But it runs this one and then it can switch and run this one, then it can run this one and it can run this one; and so by spawning multiple threads, our program doesn't necessarily run faster, but what it does give us the capability of doing is running one section of our program and then while the other is running in the background, we can continue to work with another section and it appears to us to be running a lot faster because we are doing two things at once. A good example of this that I'll show you a little later, is the ability to open multiple windows or multiple forms and be able to continue working, where with the single thread you have to satisfy one form before you can go the next one. So we'll take a look at that in just a few minutes. Now let's talk about exactly what's happening here; multiple lines are being handled simultaneously. Now there are some pros to this and obviously it is that our programs are more user friendly, things could be running in the background while we are doing something else in the foreground. And this really makes us feel better about our programs and the times that it takes for them to run. A good example of this is the spell checker in word. Now while you are running word and you are typing, on a separate thread that has been spawned in the background, the spell checker begins to watch the words you type. And every word you type it is comparing to a list, and if it sees one is misspelt that background thread checks that and then puts a little squiggly line under it to inform you that that particular word has been misspelt. And so that's a good example of how threading makes your life better when we are working on the PC. Now there are some cons to threading, and we need to be aware of those, and we'll talk about them more later. But obviously the more threads that we spawn, the more our processors have to switch between these and it can become inefficient at some time point. So that's a thread, that's a visual representation of threading and in the next video, we are going to actually look at a program and watch it spawn different threads and see how it behaves.
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