A failure to read the data on a storage or memory device. Although it is not a routine phenomenon, magnetic and optical recording surfaces can become contaminated with dust or dirt or be physically damaged, and cells in memory chips can malfunction. When a read error occurs, the program will allow you to bypass it and move on to the next set of data, or it will end, depending on the operating system. However, if the damaged part of a disk contains control information, the rest of the file may be unreadable. In such cases, a recovery program must be used to retrieve the remaining data if there is no backup.