GEOS subroutines that are able to return errors, return one of the following error numbers in the X register. 1 Not enough blocks on the disk 2 Illegal track or sector. 3 Disk full, insufficient space. 4 Directory full 5 File not found. 6 Attempt to deallocate an unallocated block. 7 Illegal VLIR chain number. 8 VLIR file error; illegal track or sector specified. 9 Too many VLIR chains, out of records. 10 File is not a VLIR file. 11 End of file, file too long. 13 Device not present. 31 Write protect is on. 32 Read error, no sync character. 35 Disk drive FDC errors: 2 Header block not found. 7 Verify error after write. 9 Header block checksum error. 10 Data block too long. 11 ID mismatch error. 37 Write verify error 38 Disk is write protected. 38 Disk drive FDC errors? 4 Data block not found. 5 Data block checksum error. 39 Write error. See VerWriteBlock.