The book is wrong. The command should be MOVE $0570,$C4,-4 to install the extension. Looking at the BXL listing, the FMOVER and EXPMOVE routines are strange. I suspect that whoever implemented the MOVE command didn't realize that the requirements for those two routines are very specific and the code in the XMOVE cartridge routine doesn't set the stage properly.   It should be possible to disassemble the BXE extension file and rip out the routines that BXL is missing and add them to the BXL ext