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Method and apparatus for controlling usage of a programmable computing machine

  • US 4,246,638 A
  • Filed: 09/14/1978
  • Issued: 01/20/1981
  • Est. Priority Date: 09/14/1978
  • Status: Expired due to Term
First Claim
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1. A method of preventing unauthorized use of a program on a programmable computing machine which operates in accordance with uncoded machine language operation codes, comprising:

  • (a) encoding the uncoded operation codes of instructions of the program as a function of location of the instructions of the program in a memory and as a function of the state of the machine prior to using the program on the computing machine; and

    (b) adding to the computing machine a decoder to decode the encoded operation codes to perform the object of the program.

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