When a component-file operation fails because the operating
system reports an error, APLX usually generates a FILE I/O ERROR (error code 17
in LER, or 6 9 in ET). The niladic system
function FERROR returns a character vector with further information (if available) from the operating system about what caused the
error. For example:
FLIB 'C:\JIM\REGIONS' The system cannot find the path specified. FILE I/O ERROR FLIB 'C:\JIM\REGIONS' ^ ET 6 9 FERROR The system cannot find the path specified.