This method was found on a batch of disks from Xavier Educational Software. The disc is 40T DFS but with track 1 not formatted. This defeats *BACKUP.
The catalogue is hidden by using VDU21,VDU3 as the title for the disc and for a dummy file physically at the end of the catalogue. This has the effect of disabling screen and printer output so preventing *CAT, *INFO *.* and *COPY *.*.
!BOOT is a machine code file which runs at &1900 and loads 1 sector from T0 S7 into &2000 and executes it. The code at &2000 then attempts to load data from track 1. If the load is successful the screen is cleared and the text 'formatting' is output and the code hangs in an endless loop.
An unsuccessful attempt to load data from track 1 (normal for the genuine disk) *RUNs a file. The directory for this file is variable between titles as is the file name.
!BOOT was renamed to OLDBOOT to preserve the original protection mechanism.
The code in !BOOT was edited so that a JSR &FFF1 was changed to JMP &FFF1. This had the effect of loading the code from T0S7 at &2000 and exiting to BASIC.
This code at &2000 was edited to remove the attempt to load the unformatted track 1 and check that it was unformatted. The file was saved as MC1 onto the RAM disc.
A new !BOOT was made which did *RUN MC1. The boot option was changed to EXEC using *OPT 4 3.
© 2018 - 2019 flaxcottage.com