Tom, don't type the line numbers from that Web page. You simply want to "open" one location at a time (do this by entering the address in octal, followed by a forward slash, no spaces anywhere), and after ODT has displayed the (in this case meaningless) previous contents of the memory word, you want to replace it with the appropriate octal value. Replacing and opening the next location in sequence can be done in one step by using the "line feed" key instead of "return". If your keyboard has no key labelled "line feed", Control-J should do instead. When done, you start the program by entering the start address (1000 in this case) and typing G (for "go"). I believe setting up the status register and stack pointer, as mentioned in the comment at the top of the listing is more cautious than you need to be here. The procedure would then look like this (the <LF> means press "line feed", <CR> means the return key): 173326 @1000/XXXXXX 12700<LF> 1002/XXXXXX 100240<LF> 1004/XXXXXX 12701<LF> 1006/XXXXXX 177170<LF> ... yada yada yada... 1132/XXXXXX 0<LF> 1134/XXXXXX 5007<CR> @1000G Hopefully, you will see your RT-11 booting here. If not, you have most probably mutated the program by spotting one of these digits wrong. If it is not yet overwritten, you can go back from the @ prompt by entering the address again, followed by the slash, e.g.: ... 1004/XXXXXX 17201<LF> <- typo, two digits reversed 1006/XXXXXX <CR> <- press return to exit @1004/017201 12701<LF> <- open location 1004 again, enter corrected value 1006/XXXXXX 177170<LF> <- continue entering code ... Tom Leffingwell wrote: -- Andreas Freiherr Vishay Semiconductor GmbH, Heilbronn, Germany http://www.vishay.com