If a File I/O Library subroutine encounters an error, processing is halted and the error level is set to the number of the error encountered. The value can be retrieved through the built-in function errorlevel. When no errors are detected, errorlevel contains the value zero. GetError( ) is a subroutine which sets a string variable to the error message associated with the error level passed to it. GetError( ) is defined in the include file (FILEIO.INC).