A POS system includes a plurality of electronic device, at least a specified one of which automatically generates and updates a history data at intervals, and an intelligent device installed in the specified electronic device for automatically updating and showing a life percentage information of the specified electronic device according to the history data. The intelligent device includes: a signal transmission module electrically connected to the specified electronic device for receiving the history data therethrough; a processing unit generating a life percentage value according to the history data of the specified electronic device, and issuing a life percentage status signal indicative of the life percentage value; a storage module for storing the history data; and a prompt displaying module visibly disposed for displaying the life percentage information in response to the life percentage status signal.