RECORDING MEDIUM AND READING SYSTEM

A medium judgment program is recorded on an information recording medium. The program causes a computer to judge whether the medium is authorized. The judgment may be based on information on a unique value preformed in the medium in regard to each of the media. If the computer determines that the information recording medium is right or authorized, the program permits the computer to reproduce a main program. The main program is different than the medium judgment program. If the computer determines that the information recording medium is wrong or unauthorized, the computer is prohibited from reproducing the main program.