We present a computational model for Szilard's engine and the information discarding process. Taking advantage of the fact that the one is essentially the reversed cycle of the other, we can discuss both by employing the same model. Through numerical simulations Ne calculate the work extracted by the engine and the heat generation in the information discarding process. It is found that these quantities depend on some realistic ingredients, which means that the work done by the engine is no longer canceled by the heat generation in the information erasure.