| 摘要 |
The protection system has a first coder that modifies the words in part at least of the program before it is recorded on the disc. The coding uses the first part of a key, and encodes the addresses of the second part of the data using the second part of the key. A coder/decoder unit is connected between the processor and the computer memory. The decoder (56) decodes the data bits when they are read from the memory by the processor, and a second coder (46) code the addresses at which are read the data bits in the memory under the second key. The buyer for the disc must first communicate a code to the vendor, who encodes the disc with this code and another code they provide to the buyer. The code is stored in EPROM in the computer.
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