fig1 is a block diagram illustrating the movement of digital data files from / to a digital data player , which is provided for the description of a digital data file duplication prevention method according to the present invention . a personal computer terminal 1 is connected to a communication network ( not shown ) such as the internet for downloading a digital data file , which is supplied at a charge or free of charge . the personal computer terminal 1 stores the downloaded digital data file on a hard disk therein and reproduces the stored digital data file or downloads it to a digital data player 2 . when the digital data player 2 intends to upload its digital data file , the personal computer terminal 1 checks an identification ( id ) code in a header of the digital data file and permits the uploading within restrictions in accordance with the checked result . the digital data player 2 stores the digital data file downloaded from the personal computer terminal 1 in a digital data storage medium 3 and reproduces the stored digital data file . also , the digital data player 2 reproduces an output digital data file received from a digital data vending machine 4 or an encoder 5 , or the digital data player 2 uploads the received digital data file to the personal computer terminal 1 . the digital data storage medium 3 is made in a removable form and stores the digital data file from the digital data player 2 therein . alternatively , as shown by dashed lines , the digital data file is directly downloaded to the digital data storage medium 3 , or , within the restrictions associated with the header , is directly uploaded from the digital data storage medium 3 to the personal computer terminal 1 . the digital data vending machine 4 is connected to a communication network such as the internet and is installed at a roadside or a public place where many people pass , for selling digital data files at a charge . the encoder 5 downloads a digital data file transmitted over a specific transmission line and supplies the downloaded digital data file to the digital data player 2 . as with the personal computer terminal 1 , digital data files could be directly downloaded from the digital data vending machine 4 or the encoder 5 to the digital data storage medium 3 ( not shown ). now , a detailed description will be given of the digital data file duplication prevention method according to the present invention with reference to fig1 and 2 . firstly , the user has to register with a digital data file supplier in order to receive a digital data file from a digital data server ( not shown ). for user registration , the user is assigned an id number and password from the digital data file supplier . then , the user downloads a digital data software player in a software form from the digital data server through the communication network and sets the downloaded digital data software player as a digital data software player in the personal computer terminal 1 . thereafter , in order to download a desired digital data file from the digital data server through the personal computer terminal 1 and communication network , the user may have to pay a corresponding charge to the digital data file supplier and transmits his id number and password to the digital data server through the personal computer terminal 1 and communication network . the digital data server identifies the user on the basis of the transmitted id number and password , and supplies the desired digital data file to the user in accordance with the identified result . at this time , the digital data server appends an id code “ 01 ” to a header of the desired digital data file to inhibit that file from being uploaded , and transmits the resultant digital data file to the personal computer terminal 1 . the personal computer terminal 1 stores the digital data file transmitted from the digital data server on the hard disk therein . under this condition , upon receiving a reproduction request from the user , the personal computer terminal 1 decrypts and reproduces the stored digital data file through the digital data software player . as a result , the user is able to listen to the desired music when the digital data file is an audio file such as an mp3 file and / or view the video when the digital data file is a video file such as a jpeg file at any time through the personal computer terminal 1 . if the user intends to reproduce ( listen and / or view ) the digital data file purchased along the above path using the digital data player 2 , then the personal computer terminal 1 downloads the purchased digital data file to the digital data player 2 . then , the digital data player 2 stores the downloaded digital data file in the digital data storage medium 3 , which is preferably made in the form of a removable memory card . if the user requests the digital data player 2 to reproduce the digital data stored in the digital data storage medium 3 , then the digital data player 2 reads the stored digital data file from the storage medium 3 and reproduces it through a decoder therein . as a result , the user can listen and / or view the digital data file anywhere using the digital data player 2 . on the other hand , in the case where a user tries to load a digital data file received along the above path , but via a different personal computer , to the personal computer terminal 1 or to upload it through the digital data player 2 , the personal computer terminal 1 identifies the digital data file on the basis of the id code “ 01 ” and thus inhibits it from being loaded or uploaded . secondly , an id code “ 00 ” is assigned to a header of a digital data file which is distributed without restriction ( e . g ., free of charge ) to the personal computer terminal 1 on the communication network . if the user receives such a digital data file through the personal computer terminal 1 , he can reproduce the received file freely through the personal computer terminal 1 or digital data player 2 as stated previously . namely , when the user tries to upload the unrestricted digital data file from the digital data player 2 to the personal computer terminal 1 , the personal computer terminal 1 identifies the digital data file as unrestricted on the basis of the id code “ 00 ”, and thus permits that file to be uploaded without restriction . thirdly , an id code “ 10 ” is assigned to a header of a digital data file which is distributed with limited restrictions ( e . g ., at a charge from the digital data vending machine 4 installed on a city roadside or a public place where many people pass ). for example , in a preferred embodiment , limited restriction digital data may be uploaded once . if the user receives such a limited restriction digital data file and tries to upload the limited restriction digital data file from the digital data player 2 to the personal computer terminal 1 , the personal computer terminal 1 determines on the basis of the id code “ 10 ” that the digital data file has limited restrictions ( e . g ., was sold from the digital data vending machine 4 ) and permits that file to be uploaded only once . after permitting such uploading , the personal computer terminal 1 changes the id code from “ 10 ” to “ 01 ” to inhibit further uploading . as a result , the user is able to upload the limited restriction digital data file only once to the personal computer terminal 1 . fourthly , an id code “ 11 ” is assigned to a header of a digital data file transmitted through a particular means , such as the encoder 5 , and purchased under a desired contract with a supplier . in the case where the user downloads the digital data file through the encoder 5 and tries to upload the downloaded digital data file from the digital data player 2 to the personal computer terminal 1 , the personal computer terminal 1 determines on the basis of the id code “ 11 ” that the downloaded digital data file was transmitted through the encoder 5 and thus permits that file to be uploaded with no restriction . while being described as resident at the personal computer terminal 1 , the method according to the present invention is , in a further embodiment , initially stored as a program on a recording medium such as a magnetic or optical disk . this program is then uploaded to the personal computer terminal 1 . alternatively , this program forms part of the digital data player 2 transmitted to the personal computer terminal 1 . as apparent from the above description , according to the present invention , the digital data file is assigned with a code capable of identifying a provider . for example , when the digital data file is purchased at a charge and intended to be uploaded from the digital data player , it can be permitted to be uploaded under certain restrictions according to its code value . therefore , the digital data file can be prevented from being illegally duplicated . although the preferred embodiments of the present invention have been disclosed for illustrative purposes , those skilled in the art will appreciate that various modifications , additions and substitutions are possible , without departing from the scope and spirit of the invention as disclosed in the accompanying claims .