Many comments suggest that the differences between the play of human and computers.
A good human player will generally come up with some kind of plan and follow up with moves that are consistent with that plan. In practice, he may have to respond to his opponent's play. There may be direct threats that he cannot ignore or he may find a need to come up with a new plan when it has become apparent that the original plan is no longer workable. Chess programs generally perform an exhaustive search through sequences of moves and select the move that leads to the best evaluation of the position that arises after the opponent has made the best moves (as determined by the result of the evaluation). Consequently, computers tend to be deadly in tactical situations; oversights by the opponent are ruthlessly exploited. Also, they often defend difficult positions well; sometimes by finding moves that appear, at first sight, to be ridiculous to a human. However, a major weakness of computer chess programs concerns the evaluation criteria. If a forced checkmate is available, this is obviously going to be the preferred choice. In the absence of this possibility, material is easy to measure and, as a result, tends to be heavily weighted; this is reflected in the decidedly materialistic play play of most computer programs. However, other positional considerations are more subtle and a good human player can be at an advantage here. For example doubled pawns are usually considered to be a weakness (the pawns cannot form a chain where each pawn is protected by another). However, there may be ample compensation; the pawns may control critical squares and the accompanying half open file may be put to good use by the rooks. In this, and many other situations, the assessment of whether a particular feature of a position is good or bad depends on many factors and will change as the position evolves with further moves. In this example, the doubled pawns might be desirable in the middle game, but a liability in the endgame where their vulnerability becomes important. A strong human player will have ability to make good judgements as to the implications of his potential choices. Computers are generally much weaker in this respect. In closed positions, it is not unusual to see computers making aimless moves, for example indecisively moving a piece back and forth between two squares, whereas the strong human player will try to find a plan for gradually improving his position and forcing positional concessions on the part of his opponent. Also, computers will sometimes leave their king weakly defended while they pursue material advantage elsewhere on the board.
The result is that there are definite differences in the style and conduct of the play between strong humans and computer programs.
