Can anybody tell me how computer programs arrive at the scores in analysing games? I often send a game in for analysis, and note that it gives a score after each move that I suppose indicates which side has the advantage at that stage. Is there any simple procedure, apart from calculating pawn values, whereby one can do this by yourself to evaluate moves when playing against an opponent? I think this could especially be helpful when playing chess 960 as there are no pre-analysed opening "book" moves available as far as I know.

I used to have the source code for a chess playing engine. In examining such, one found - of course - counting out of the material edge that one side had over the other, using standard point counts for pieces. However, to that must be added or subtracted other adjustments (e.g., positional imbalances, king safety, two two bishops, pawn breaks, development differences, etc.). Each program differs in how they weight these other adjustments - making one engine play aggressively and another soundly.

You might get hold of the code for Crafty and see what's inside. There, you might find a starting point for your quest.