On Sun, 21 Dec 2003, Rich Sias wrote: This reminds me of an interesting technique I saw implemented on the Apple ][. Apple's low-level disk sector format has a three byte sector header prolog and epilogue, and a three byte data prolog and epilogue. But the third byte of the epilogue is basically ignored. So you can format a disk and use a non-standard byte for the third epilogue byte. When you use a fast copy program, it will write the new disk out using the standard epilogue bytes. So some pirate wrote some code that would check the third epilogue byte to see if it was modified. If not, it would run a short routine that would ask you to enter your name, and it would then add it to a list and show you all the other people your copy had passed through. It would then write out the modified epilogue byte to a certain sector and you would never see that routine again (until you copied the disk again and then it would appear on the new disk). It was a very clever way to know when a disk was copied. This wouldn't work if you used a bit copy program because that would copy the disk verbatim (i.e. including the modified epilogue byte). -- Sellam Ismail Vintage Computer Festival ------------------------------------------------------------------------------ International Man of Intrigue and Danger http://www.vintage.org [ Old computing resources for business || Buy/Sell/Trade Vintage Computers ] [ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]