Analysis engines, are programs to analyse chess positions. These applications evaluate all legal moves, considering the different variations that rise up from each one of them up to a certain depth. They are the base of the chess programs available today..
There exists quite a few of those engines, some of them categorized as commercial (since you need to pay to use them) and some others completely free of charge. The commercial engines are the most powerful (Rybka; Shredder; Fritz; etc,), however some of the free engines perform very well (Rybka; gown; Ruffian; Arasan, and so on,)
though they do not offer as many options as the commercial ones and their graphical interface tend to be very inferior, or nonexistent. The viewer is ready to perform very well even when using the free engines.
In order that the viewer can use an engine, it must be compatible with the Universal Chess Interface (UCI), for example:
Rybka is, undoubtedly, the more powerful chess engine as of today, from its appearance it has marked a notable difference with the rest. The last version is the 3.0, with an Elo of 3140 (3242 with 4 processors). It's a commercial version that costs 36 euros, but version 2.2n2 is totally free. This version has an Elo of 2943 and is perfect to play chess with The Viewer and to analyze as well. We have included that Rybka version as one of the add ons that can be installed automatically with only one click.
To use an engine with the Viewer, the first step is to "register it" by the option "Calculation modules (Engines )". Pressing the button ) opens up a window in which it is necessary to specify the
path leading to the executable file of the engine. To specify the path you have to use the button which allows to browse your PC's file system until you find it.
Once the path is specified, the engine will be visible on the list of all registered engines. You can view all the options that can be adjusted for this particular module. Each engine has it's own set of options, most of them being common to a good number of different engines.
The first time you can simply leave the default values selected and press the "OK" button to complete the engine registration.
To analyse a position, a game, or list of games with any of the registered engines, you use the auxiliary board. The engines are also used to search for novelties in collaboration with the games database.
The viewer allows to use the engines to analyse on the spot, a game that is being played or broadcasted in the online meeting room. This option will not be available for the two players who are actually playing the game.
Analysis engines. 
which allows to browse your PC's file system until you find it. 
