Once computer data is printed on paper, it becomes out-of-sync with computer database updates. Paper is difficult to search and arrange in multiple sort arrangements, and similar paper data stored in multiple locations is often difficult and costly to track and update. A paperless office would have a single-source collection point for distributed database updates, and a publish-subscribe system. Modern computer screens make reading less exhausting for the eyes; a laptop computer can be used on a couch or in bed. With tablet computers and smartphones, with many other low-cost value-added features like video animation, video clips, and full-length movies, many argue that paper is now obsolete to all but those who are resistant to technological change. eBooks are often free or low cost compared to hard-copy books.