evaluating a position

I Recently i downloaded chess program from chess.com resources. It is most downloaded there. Rybka v2...something. Anyway it is excelent for analysing games. Now i need a little help with it. After every move, it gives many lines how game can be countinued and score( i gess this is evaluation) , when whites  plays it gives for example -0,50 and when black responds now it is +0,50. Who here have a half pawn advantage. Does anyone downloaded this and is there some more helpfull features on this program. Thanks.

I'm guessing you have Rybka v 2.2 if you got it free. What is your GUI? I don't think they all display the engine's analysis in the same format.

Regardless, it typically scores the game from the point of view of the player to move, with 0 being neutral. That means if it is white to move, and it says +0.50, white has a half pawn advantage, but if it is white to move and it says -0.50, white has a half pawn disadvantage (and therefore black has the advantage). Obviously the reverse would be true for black to move.

thanks. And what is GUI?

GUI - Graphical User Interface. The display that you can see. Rybka is a chess engine.

It doesnt matter who is going to move. The game is always analysed from white's point of view. If its showing a positive value white has an advantage,while negative value means that white has a disadvantage.

thanks, but is there a posibility for example, if i am analysing a game that  I played and now at some point of the game i want to try some move or a line that machine isnt't showing and i want it to avaluate that move (line). Could I do that, and if I can, how?

That is not true of the prog he uses. I'm guessing he is using Arena, since that is the most common free GUI to download Rybka 2.2 onto, and what he's describing sounds like what I see. This definitely scores each position from the point of view of the player to  move when analyzing or moving (e.g. +M2 when white is going to mate black in two and white to move, then -M2 when it is black to move, then +M1 white to move, then checkmate).

yes you can do that, but what GUI are you using. I'm guessing arena -- I don't like arena and can't help you with it... there are arena users here who can I'll wager.

By the way, about the + and - ... there are two ways of scoring a position. The way that changes with whoever has the move (positive for person with the move), and the way where it is constant, positive good for white, negative good for black.

You're GUI is configured for the "changes with the move" evaluation, which was the first style, but it has been pretty much abandoned. It has become standard to use + for white and - for black in a constant way. It's like algebraic notation vs. descriptive... the war is over, Algebraic won. Same for the computer evaluations... this issue has been decided -- If you can figure out how to change your GUI to + for white's advantage regardless of who has the move, you should. As far as I know, Arena is the only GUI that has that as the default evaluation style. Last time I tried it was a royal pain in the ass to get Arena to do it right, too.  Sorry. Again, some Arena user here can probably tell you how to switch, I can't remember how it's done. 

Thanks men, your information are helpful, I'll try to manage somehow. And the way you  explained I think it's Arena. I am not sure becouse i don't have much expirience with these programs and computers.