Error messages are displayed each time SuperMemo can detect any abnormality in the status of the learning process, structure of the database, environment conditions or user's actions.
The three major classes of error messages are:
* warnings - inform the user of the detected irregularity. They can usually be successfully responded to by pressing an appropriate key or changing a program's or system's parameter
* database integrity error messages - inform the user of the integrity problems detected in the database. Very often, integrity errors can be remedied by using Tools : Recover or RESCUE.EXE without any loss of data. However, if not properly responded to, integrity errors can propagate, or result in a fatal error, and consequently produce a significant damage to the database
* fatal error messages - indicate that SuperMemo or Windows encountered a problem it was not able to cope with. Fatal errors usually result from serious database integrity problems, software or hardware problems (often independent of SuperMemo)