Chess computer / software games - question!

Hi, I'm new to this forum, and pleased to be here :-)

Just started playing chess again after several years' break - and wow, am I hooked or what!  I also downloaded a chess app for my phone, so I can play / practice when my friends aren't around - and it got me thinking:  How do these computer chess games regulate 'difficulty'?  I mean, usually they offer levels of difficulty, say from 1 - 10.  But surely, if a piece can be moved to gain an advantage against you, it'll be moved.  How would this be different on a different dificulty setting?  After all - same pieces, same number of squares, same goal etc.

Any theories / ideas appreciated!

i dont understand what you want

1200, 15, 2000 hard..... u find a setting top right what level u want to test your skill via the computer(click on your level)

One way to vary the difficulty is for the computer to spend less time checking moves. For example, on one setting, it might check all promising moves out to a depth of 20 ply (10 moves for each player), while another setting might only check all promising moves out to 4 ply (2 moves for each player). When it checks to 20 ply, it will play much stronger moves than when it checks to 4 ply.

Another way it can play less than optimal chess is to calculate the top N lines, and play a non-optimal line. For example, if you have it set on an easy setting, it might calculate the top 5 lines to 10 ply and once in a while play a sub-optimal move (e.g., the 4th best move, which results in losing a pawn if you spot the tactic).

There are many other ways it could play sub-optimally as well. Basically, if you consider all the different factors the computer takes into consideration to determine the best move (piece activity, king safety, material, etc.) and the different weights it has for those factors, it could weight any of those inappropriately. For example, it might weight king safety very low and get itself into a bad position because the king is still in the center and you have a raging attack in progress.

I don't know all the different ways that computers do in fact vary their strength, but those are some of the obvious ways that they could vary their strength, and I know for a fact that they do at least vary thinking time (and thus calculation depth) to change their strength.

Thanks sapientdust, that's the answer I was looking for!  it makes a lot of sense what you say - I knew that there must be other factors involved; I just wasn't advanced enough in my understanding of chess to know what they are.  It helps, actually, to know these things - gives me a bigger picture of the game :-)