System with software usage timer and counter for allowing limited use but preventing continued unauthorized use of protected software

A method for preventing continued unauthorized use of protected computer software in a data processing system including a clock, storage means and a counter comprising the steps of:

• providing an initial time setting for said clock at the time of installation of the software in said data processing system;
• providing a constant representing a predetermined amount of time in said storage means at the time of installation of the software;
• incrementing the counter each time that the protected software is operated;
• making a first determination whenever the protected software is operated as to whether the constant has been provided in the data processing system;
• making a second determination as to whether the counter has reached a predetermined value;
• making a third determination as to whether the current time sensed from said clock exceeds the time when the software was installed by an amount equal to or greater than said constant;
• if any of the first, second or third determinations are true, sending a warning message to the software user indicating unauthorized use, setting the constant to a predetermined multiple of the current time setting, and switching the counter to cause it to commence decrementing from the setting at which it stood when switched;
• decrementing the counter each further time that the software is subsequently operated;
• and
• causing the software to be disabled when the counter has been decremented to a second predetermined value.