Hospitals are trading their once-scattered medical charts, file folders, X-rays, and other documents for a unified electronic records system accessible with a few keystrokes. Federal officials who are trying to convince more hospital executives to go "paperless" say electronic records can make hospitals more efficient, reduce medical errors, and lower health-care costs. The costs of the transition can be high, and many physicians are also unwilling to trade the ease of jotting down paperbound notations of their patients' statuses for a system that requires them to type the same information into a computer.