reference will now be made in detail to the present embodiments of the present invention , examples of which are illustrated in the accompanying drawings , wherein like reference numerals refer to the like elements throughout . the embodiments are described below in order to explain the present invention by referring to the figures . fig3 is a block diagram of a portable device 300 adopting a file management method according to an embodiment of the present invention . first , the portable device 300 is connected to a personal computer ( pc ) 370 , and is disconnected from the pc 370 when a playlist is created . a user creates and / or stores desired music files , folder - by - folder , in the pc 370 , and the pc 370 acts as a source server to provide the files to the portable device 300 . referring to fig3 , the portable device 300 includes a control unit 310 , a memory unit 320 , a display unit 330 , a user input unit 340 , a universal serial bus ( usb ) port unit 350 , and a digital - analog converter ( dac ) unit 360 . the memory unit 320 stores programs to control general operations of the portable device 300 and a program to control the automatic creation of a playlist according to an embodiment of the present invention , and temporarily stores data produced in the course of executing the programs . specifically , the memory unit 320 includes a file table to store information on files in a unit of a folder , which has been copied from the pc 370 , and a playlist table to store file list information . the user input unit 340 includes keys to allow the user to input numeral and character information , and functional keys to set various functions . however , it is understood that according to other aspects , the user input unit 340 includes other devices and methods to receive inputs from the user , such as a rotatable dial and / or a touch screen . the display unit 330 displays user interface information output from the control unit 310 . the dac unit 360 converts audio data , which has been decoded in the control unit 310 , into analog audio signals and outputs the analog audio signals to speakers , earphones , and / or an external device . the usb port 350 complies with the interface standard to connect the portable device 300 to the pc 370 . it is understood that according to other aspects , connection devices and methods other than usb are used , such as a bluetooth unit to connect to the pc via a bluetooth connection or an infrared unit to connect to the pc via an infrared connection . the control unit 310 controls general operations of the portable device and / or decodes audio and / or video data stored in the memory 320 . specifically , the control unit 310 copies files that are to be played , folder - by - folder , while connected to the pc 370 through the usb port 350 , determines if there are added or deleted files by checking a file system through , for example , a file allocation table ( fat ) when the files are completely copied , and creates a playlist of the files copied folder - by - folder according to a change in the file system . fig4 is a block diagram of the control unit 310 illustrated in fig3 . referring to fig4 , the control unit 310 includes a folder configuration unit 410 , a file detecting unit 420 , and a list creating unit 430 . the folder configuration unit 410 copies the files that are to be played from the pc 370 through the usb port 350 , folder - by - folder , and stores the files in the file system corresponding to the fat . according to an aspect , information on the files copied in the file system includes an index number , a file path , a physical memory start address , a file size , and table new / old information . the file detecting unit 420 determines whether there are added or deleted files by checking for changes in the file system . when the file detecting unit 420 determines that there is an added file , the list creating unit 430 analyzes path information of the file , creates a playlist title , and stores information on the added or deleted file ( such as an index number , a file name , and a playlist title ) in a playlist table . fig5 is a flowchart of a method of managing files of a portable device 300 according to an embodiment of the present invention . first , the portable device 300 is connected to a pc 370 ( operation 510 ). the portable device 300 sets a check flag to 0 in a file system ( operation 520 ). then , the portable device 300 transmits a unique id value to the pc 370 according to the media transport protocol ( mtp ) standard ( operation 530 ). for example , if id values of files used in the portable device 300 are 1 , 2 , 3 , and 4 , an id value transferred to the pc 370 is 5 . this id value becomes the standard to set the index number of a file inside the pc 370 . for instance , the pc 370 sets indices of files as 5 , 6 , 7 , and so on . at the same time , a “ portable device / media ” folder is created in a screen of the pc 370 connected to the portable device 300 . the user creates folders including files that he or she desires to be played using a searching program on the pc 370 . next , the user searches folders in the portable device 300 using the searching program , such as the windows searching program illustrated in fig6 a . then , the user copies the playlist folder - by - folder from the pc 370 to a media folder of the portable device 300 , as illustrated in fig6 b . afterwards , the portable device 300 checks if the files are copied to the portable device 300 using a write enable signal ( operation 540 ). then , the check flag is set by checking the file system ( operation 542 ). when the files are input from the pc 370 to the portable device 300 on a folder - by - folder basis , the files are copied to a buffer memory of the portable device 300 ( operation 544 ). referring to fig6 b , in the windows screen , an “ up - to - date - song ” folder is copied to the media folder of the portable device . the directories illustrated in fig6 b can be displayed as a tree - like structure including folders and dependent files . then , the files are copied from the buffer memory to a storage unit in the portable device ( operation 546 ). the storage unit may be , for example , nand flash memory , nor flash memory , or a hard disk drive . the portable device 300 then stores information on the copied files in , for example , a fat on a record - by - record basis ( operation 548 ). fig6 d shows an example of the fat storing the file information according to an embodiment of the present invention . an index number , a file path , a physical memory start address , a file size , a file name , and table new / old information of each file in the “ up to date song ” folder is stored in the fat . for example , referring to fig6 c and 6d , in the case of “ 1 . mp3 ”, an index number is “ 1 ”, a file path is “ root / media / up - to - date - song ”, a physical memory start address is “ 20 ”, a file size is 20 bytes , and table new / old information is “ new ”. the table new / old information indicates if the file is registered from the file table to the playlist table . when all files to be copied are completely copied , the portable device 300 confirms if the disconnection from the pc 370 is complete ( operation 550 ). when confirming the disconnection from the pc 370 , the portable device 300 detects if there are added files which must be registered in the playlist table by checking the file system ( operation 560 ). for example , when the check flag of the file system is set to 1 , the portable device 300 determines that added files are present . with reference to the table new / old information in the fat , the portable device 300 counts the number of added files ( operation 562 ). for example , if the number of files which have not been registered from the file table to the playlist table is five ( that is , the number of files that have a table new / old information entry of “ new ”), the number of the added files is five . then , file information of a first file , stored on a record - by - record basis in the fat corresponding to the file system , is read ( operation 572 ). file path information of the first file is analyzed , and the last file directory or folder in the file path information of each record - by - record based file is registered in the table as a playlist title ( operation 574 ). for example , the file path of a file ( 1 . mp3 ) corresponding to an index number 1 is “ root / media / up - to - date - song .” therefore , the playlist title is “ up - to - date - song ,” which corresponds to the last folder in the file path . then , the index number , the file name , and the playlist title of the file are stored in the playlist table , and a playlist table registering of the next added file is performed in the same manner ( operation 576 ). the operations 572 through 576 are repeated until the file number count becomes “ 0 ” ( that is , all of the added files are registered in the playlist table ). finally , in the playlist table , file information is stored as illustrated in fig6 e . that is , referring to fig6 e , the playlist table includes an index number , a file name , and a playlist title of each file . aspects of the present invention can be written as computer programs and can be implemented in general - use digital computers that execute the programs using a computer - readable recording media . examples of the computer - readable recording media include magnetic storage media ( e . g ., rom , floppy disks , hard disks , etc . ), optical recording media ( e . g ., cd - roms , or dvds ), and storage media such as a computer data signal embodied in a carrier wave including a compression source code segment and an encryption source code segment ( e . g ., transmission through the internet ). the computer - readable recording medium can also be distributed over network - coupled computer systems so that the computer - readable code is stored and executed in a distributed fashion . according to an aspect of the present invention , a portable device 300 ( such as an mp3 player or a mobile phone ) creates a playlist automatically on a folder - by - folder basis without a user having to additionally create a playlist , thereby enabling the user to manage files conveniently . although a few embodiments of the present invention have been shown and described , it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention , the scope of which is defined in the claims and their equivalents .