1. A method of discriminating, for each first level partial data, whether or not saved data, one file of which is composed of a plurality of the first level partial data and each of the first level partial data is able to include a second level partial data, has been unjustifiably rewritten, said method comprising steps of: (a) at a time of saving a file, designating a first level partial data on the basis of a user instruction; receiving a password from a user; converting the received password and the designated first level partial data, which includes a second level partial data, according to a predetermined procedure to generate a first code; and saving the file with storing of the first code to correspond to the designated first level partial data; (B) at a time of reading the saved file, reading the saved file; designating the first level partial data on the basis of a user instruction; receiving the password from the user; converting the received password and the designated first level partial data, which includes the second level partial data if the designated first level partial data includes the second level partial data, according to said predetermined procedure to generate a second code; comparing the generated second code with the first code stored to correspond to the designated first level partial data; and discriminating that the designated first level partial data has been unjustifiably rewritten if comparison results in a fact that the first code is not equal to the second code.