| 摘要 |
PURPOSE:To prevent a lent program from being used after the expiration of lending by comparing information of the number of days till the expiration of the validity time recorded on an external file with the number of days of the use obtained from date information in a computer. CONSTITUTION:Data 7 of the number of days of validity is written on a file of a floppy disc 6 to which the term of validity should be given. Use start data 8 is read before this file is used, and the date obtained from a date information device 4 of a computer at this time is written as data 8 if nothing is written as data 8. If data 8 is set,the number of days of the use is calculated in accordance with its date and date information obtained from the device 4. This number of days of the use is compared with data 7 by a comparator 2, and this file is handled as a file which is within the term of validity and can be used only when the number of days of the use is smaller than date 7. In this system, the file is not used after the expiration of lending even in a computer where date information is not correctly set. |
