NVDA is a free, open source screen reader. A screen reader is, in this case, a software program that makes a computer talk, allowing blind or visually empaired people to use computers. NVDA is a very small program that can run on systems running Windows XP or Windows Vista, and it is ultra portable. It is written in the Python Programing language, allowing those who actively develope NVDA to do so very rapidly. NVDA stands for Nonvisual Desktop Access. The NVDA project is sponsered by NVAccess. You can find out more information about NVAccess at http://nvaccess.org.
A software screen reader needs two major components. One of these components is the software that finds out what's on the screen, and the other component is that which actually turns the information that the first component retrieves into audible speech. The second component is often called a speech synthesizer. NVDA has a very small and very responsive speech synthesizer built into it called ESpeak. ESpeak is also free, and open source. You can find out more information, or download a version that will work with other applications which can work with speech synthesizers at http://espeak.sf.net. Because ESpeak is such a small package, and because it's output is synthetic, ESpeak is among the most responsive speech synthesizers available today. Many immediately exclaim that ESpeak sounds like a robot. This is true, that it does, but there are also people who absalutely love ESpeak, such as myself. I am rather on the deaf side, so I use hearing aids. I find ESpeak just as easy to understand as IBM Via Voice or Eloquence for JAWS, and certainly easier to understand than most of the AT&T Natural Voices. Users who have difficulty understanding ESpeak may find that it becomes easier for them after some extended use of it.
As I said, NVDA uses ESpeak by default, it's installer speaks with it, and it will speak with it by default after installation. You will be able to get NVDA to use other speech synthesizers as well, SAPI4 or SAPI5 namely. NVDA cannot output to braille yet, but there are many people who are excited to get that to work, so braille support is likely to come somewhere down the road.
NVDA works by checking any controls and things like that on programs that are in focus, and attempting to grab any information that can be used to inform the user what the control is. It works very well with most of the programs that come with windows, and many more. It will work with all applications which use standard controlls. It can read tool tips, status bar information, and much more. Users of comercial screen readers will imediately notice that NVDA is ran similar to JAWS and Window-Eyes. NVDA tries to impliment the best of all worlds, so to speak, implimenting the most widely favored keystrokes for doing things with a screen reader. It should be said that NVDA doesn't try to copy a different screen reader, it tries to include the best from all of them. NVDA isn't as robust, isn't as widely used, isn't as powerful as comercial screen readers like JAWS and Window-Eyes. Since it is open source, however, NVDA offers a way for it's programmers to try out ideas that might not have been considered acceptible for comercial screen readers. An example of this is NVDA's ability to beep when a progress bar updates, rather than speaking the percentage or not knoticing it at all.
Users will find that NVDA isn't as rock solid, yes I took that from GWMicro, as comercial screen readers like Window-Eyes or JAWS. On the other hand, there are a few things that NVDA may well outperform these other screen readers at, such as speedy and snappy performance in most areas. And, guess what, are you sighted, and curious about what screen readers are and do? There's nothing stopping you from playing with NVDA. That, on the other hand, would be a very pricey question if you wanted to fiddle around with a comercial screen reader. The last thing about this is, are you a blind computer user, stuck using JAWS, Window-Eyes, or System Access, or Hal demos because you can't aford to pay a hefty price (more than your computer) just to use your computer? I admist, system access isn't so bad, Window-eyes and Hal aren't either these days, but NVDA is one of few totally free options for you.
What does NVDA Work with? This is y no means a comprehensive list, it will just get you started knowing what this free screen reader might be able to do. It works with Microsoft Office Excel somewhat, word, outlook, yes it tells you that messages are unread and stuff, internet exploror, mozilla firefox, outlook express, windows mail, duh they're the same thing but, the NVDA enterface window. Could you imagine, a screen reader that couldn't even read it's own enterface window to adjust settings and things? And a whole heck of a lot more. Oh, as a point of enterest, blind audio gamers will recall that they often have to shut down or put their screen readers to sleep before they can start playing games, because their screen readers are known to enterfeer with game play, well, guess what, NVDA doesn't, not yet, anyway. I can leave NVDA running and play games like topspeed, check the time while in the middle of a race and everything.
Ok, I've rambled on enough by now, for more on NVDA, continue reading this help, that is, assuming you haven't given up on it yet do to lousyness *lol*, or download and try NVDA for yourself from http://nvda-project.org.