Apple ProDOS Protector

Jason Coleman

These programs protect your Apple II ProDOS disks against unauthorized use by other people. If you're using DOS 3.3, see the "Guardian Angel" article elsewhere in this issue for a similar protection method.

"Apple ProDOS Protector" lets you protect any ProDOS disk from unauthorized use by others. Three files are required to make this system work. Before getting started, type in and save Programs 1-3 listed below, which are all written in Applesoft BASIC.

To begin the protection process, select the disk you want to protect, then load and run Program 1, "File Creator." The program asks you to enter a unique access code for the soon-to-be-protected disk. The access code can be any length and can contain any combination of letters, numbers, and symbols except for the comma and colon. Be sure to write the access code down for later reference—you may find it difficult or impossible to use the disk without it.

The program then creates a machine language file on disk named START.END.ML. You don't need a copy of Program 1 on the disk to be protected, only a copy of the START.END.ML file created by Program 1.

Next, you are asked to enter the name you wish to use for this disk's startup file. Make a note of this filename as well.

When Program 1 is finished, load Program 2 and save it on the disk to be protected, using the filename you selected for the startup file. Then load Program 3 and save it on the disk to be protected, too, using the filename ENDUP. The disk should now contain these three files:

1. START.END.ML, the machine language file created by Program 1.

2. Program 2, saved with the filename you selected for the startup file using Program 1.

3. Program 3, saved with the filename ENDUP.

This disk is now protected against most users. Only programmers proficient at working with the ProDOS machine language interface (MLI) can gain access without knowing the access code.

Using Protected Disks

When a protected disk is booted, the user is asked to enter the correct access code. If the access code is correct, the user is not allowed to use the disk. Anyone who doesn't know the code will not be able to break out of the program by pressing CTRL-C or CTRL-RESET.

When you are finished using a protected disk, load and run the ENDUP program (Program 3) to disable the CATALOG command so other users can't see what's on your disk.

Of course, no protection scheme is foolproof. But you should find this method sufficient to deter most casual users from accessing your ProDOS disks.

For Instructions on entering these listings, please refer to "COMPUTE!'s Guide to Typing In Programs" In this Issue of COMPUTE!.