this invention will be described in further detail by way of example with reference to the accompanying drawings . now , referring to fig2 , the concept of a digital content data distribution system according to the present invention will be described . the concept of this system is novel in that a cost is integrated with digital content data ( hereinafter also referred to simply as content ), namely a content fee is included in a communication fee as viewed from the user side , a unit price per unit data volume is set , and the content and the cost are distributed at the same time , namely cost information is attached to digital content data . in the above - mentioned digital content data distribution system , an information provider 1 which sells content sells content on demand by a user 3 . when the purchase of content is requested , cost information per unit data volume is attached to the requested content , which is then transmitted from the information provider 1 to the user 3 via an information communication network ( or a communication medium ) managed by a carrier 2 . the information provider 1 may be an individual , an institution , or a business entity who is the creator , licenser , owner , collector , manager , or distributor of content for example . the carrier 2 may be an internet service provider , a telecommunications company , or a broadcasting company for example . consequently , the information communication network may be the internet , a public telephone network , a television network , a radio network , a cable television network , and a satellite television network for example . the user 3 is charged by a fee collection service company 4 for the acquisition of digital content data . the fee is computed by multiplying the data volume of the digital content data acquired by the user 3 by the unit price per unit data volume . the cost information per unit data volume ( a unit price or information for identifying the unit price ) to be attached to digital content data can be set by the content provider 1 as desired . therefore , as shown in fig3 , for a same data volume , its fee may differ from one article of digital content data to another . the fee collection service company 4 which collected the fee for purchased digital content data from the user 3 distributes the collected fee to the information provider 1 and the carrier 2 in accordance with the agreements concluded between them . it should be noted that various combinations are possible in which the carrier 2 also serves as the charge collection service company 4 for example . the following describes an exemplary configuration of the digital content data distribution system associated with the present invention with reference to fig4 . an information providing server 5 is managed by the information provider 1 and comprises a content integration block 11 . the components , a transmission block 12 through a reception block 16 , are managed by the carrier 2 . a user terminal 6 is equivalent to a personal computer for example which is operated by the user 3 and comprises a content separation block 17 and a content reproduction block 18 . a fee collection server 7 is managed by the fee collection service company 4 and comprises a management unit 19 and a charging unit 20 . the content integration block 11 adds the cost information about a unit data volume concerned to each predetermined unit data of content and outputs the resultant digital content data to the transmission block 12 . to be more specific , the cost information is added to the header of each packet of digital content data and the resultant packet is outputted to the transmission block 12 . the cost information may be an amount of money if the unit price ( amount of money ) of a unit data volume can be determined in the management unit 19 or the information indicative of attributes ( type , quality , etc .) of digital content data ( in this case , an attribute versus information unit price table must be prepared in the management unit 19 ). the transmission block 12 converts the data format of the digital content data attached with the cost information per unit data volume inputted from the content integration block 11 into a data format suitable for the information communication network 14 in accordance with a predetermined protocol . the transmission block 12 transmits the converted digital content data to the reception block 16 via the information communication network 14 . a gating block 13 of the transmission block 12 acquires information for identifying the communication information ( attached cost information , transmitted data volume , communication time , and sender ( namely the information provider 1 ) associated with the digital content data to be transmitted via the information communication network 14 and the information about the recipient ( namely the user 3 ) and sends these pieces of acquired information to the management unit 19 . a gating block 15 of the reception block 16 acquires the information for identifying the communication information ( added cost information , received data volume , communication time , and sender ( namely the information provider 1 ) associated with the digital content received via the information communication network 14 and the information about the recipient ( namely the user 3 ) and transmits these pieces of acquired information to the management unit 19 . it should be noted that the processes by the gating blocks 13 and 15 may be executed at the same time the digital content data are transmitted and received or , after storing the communicated information , or the digital content data , for a predetermined period , the communicated information accumulated in that period may be collectively transmitted to the management unit 19 . the reception block 16 receives the digital content data via the information communication network 14 , restores the original data format of the received digital content data in accordance with a predetermined protocol , and outputs the resultant content to the content separation block 17 . the content separation block 17 separates the cost information from the digital content data and outputs the resultant digital content data to the content reproduction block 18 . the content reproduction block 18 reproduces the digital content data removed of the cost information inputted from the content separation block 17 . the management unit 19 compares the communication information received from the gating block 13 of the transmission block 12 with the communication information received from the gating block 16 of the reception block 16 . if the supply of the digital content data from the information provider to the user has been confirmed ( the confirmation may be made from the communication information outputted from one of the gating blocks 13 and 15 ), the management unit 19 computes multiplies the cost information included in the communication information by the data volume to compute the sale price of the digital content data and outputs the sale price to the charging unit 20 . also , the management unit 19 sends the usage information and charging information of the digital content data to the information providing server 5 and the user terminal 6 . the charging unit 20 charges the user 3 for the digital content data on the basis of the sale price received from the management unit 19 . the following describes a sequence of processes for providing digital content data from the information provider 1 to the user 3 and the distribution of the amount of money collected from the user 3 to the information provider 1 and the carrier 2 with reference to the flowcharts shown in fig5 through 8 . first , the content provision processing by the information providing server 5 managed by the information provider 1 will be described with reference to the flowchart shown in fig5 . in step s 1 , the information providing server 5 checks for a request for content from the user terminal 6 operated by the user 3 . this operation is repeated until a request has come . if a request for content is found , the procedure goes to step s 2 . in step s 2 , the information providing server 5 reads the requested content from a predetermined content database . each unit data volume of the retrieved content is integrated by the content integration block 11 with the cost information of that unit data volume . in step s 3 , the content integration block 11 outputs the digital content data attached with the cost information in step s 2 to the transmission block 12 . the following describes the content communication processing by the components , the transmission block 12 through the reception block 16 , managed by the carrier 2 with reference to the flowchart shown in fig6 . in step s 11 , the transmission block 12 converts the data format of the digital content data attached with the cost information inputted from the information providing server 5 into a data format suitable for the information communication network in accordance with a predetermined protocol and sends the resultant digital content data to the reception block 16 via the information communication network 14 . in step s 12 , the gating block 13 of the transmission block 12 acquires the information for identifying the communication information ( attached cost information , transmitted data volume , communication time , and sender ( namely the information provider 1 ) associated with the transmitted digital content data and the information associated with the recipient ( the user 3 )) and sends these pieces of information to the management unit 19 . in step s 13 , the reception block 16 restores the original format of the digital content data received via the information communication network 14 in accordance with a predetermined protocol . in step s 14 , the gating block 15 of the reception block 16 acquires the information for identifying the communication information ( attached cost information , received data volume , communication time , and sender ( namely the information provider 1 ) associated with the received digital content data and the information associated with the recipient ( the user 3 )) and sends these pieces of information to the management unit 19 . in step s 15 , the reception block 16 sends the digital content data restored in step s 13 to the user terminal 6 . the following describes the content usage processing by the content separation block 17 and the content reproduction block 18 which constitute the user terminal 6 . in step s 21 , the user terminal 6 requests the information providing server 5 for digital content data . in response to this request , the information providing server 5 sends the requested digital content data in the same manner as described above . in step s 22 , the user terminal 6 receives at the content separation block 17 the digital content data transmitted from the reception block 16 . in step s 23 , the content separation block 17 separates the cost information from the digital content data received in step s 22 and sends the resultant digital content data to the reproduction block 18 . in step s 24 , the content reproduction block 18 reproduces the digital content data removed of the cost information inputted from the content separation block 17 . the following describes content fee charging processing by the management unit 19 and the charging unit 20 constituting the fee collection server 7 managed by the fee collection service company 4 , with reference to the flowchart shown in fig8 . in step s 31 , the management unit 19 matches the communication information supplied from the gating block 13 of the transmission block 12 with the communication information supplied from the gating block 15 of the reception block 16 to confirm that the digital content data have been supplied from the information provider server 5 to the user terminal 6 . then , the management unit 19 multiplies the cost information ( namely , unit price ) included in the communication information by the received data volume on the side of the user terminal 6 ( namely , the transmitted data volume on the side of the information provider server 5 ) to compute the sale price of the digital content data . further , the management unit 19 computes the communication fee on the basis of the data volume and the communication time . in step s 32 , the management unit 19 synthesizes the digital content data sale price obtained in step s 31 with the communication fee and sends the result to the charging unit 20 as charging information . in step s 33 , the management unit 19 sends the usage information and charging information of the digital content data to the information provider server 5 and the user terminal 6 . in step s 34 , the charging unit 20 charges the user 3 on the basis of the charging information supplied from the management unit 19 in step s 32 . namely , the user 3 is charged for the content sale price included in the communication fee . in step s 35 , the charging unit 20 distributes the amount of money collected from the user 3 in step s 34 to the information provider 1 ( the sale price of the digital content data ) and the carrier 2 ( the communication fee ) in accordance with the agreements previously concluded between the information provider 1 and the carrier 2 . it should be noted that the above - described relationships between the content integration block 11 through content reproduction block 18 , the information provider 1 , the carrier 2 , the user 3 , and the fee collection service company 4 are not restricted to them . for example , the transmission block 12 and the gating block 13 may be arranged and managed by the information provider 1 . the gating block 15 and the reception block 16 may be included in the user terminal 6 . other variations are also practicable . fig9 shows an exemplary configuration of a digital content data distribution system in which the carrier 2 is a broadcasting company . in this example , a transmission block 12 , a gating block 13 , and a information communication 14 are prepared as a broadcasting facility network for transmitting the ground or satellite wave . in this example , a gating block 15 is included in a user terminal 6 and the usage information of the received digital content data is sent to a management unit 19 via a public telephone line for example . the charging information to be transmitted to the user terminal 6 from the management unit 19 is also transmitted via the public telephone line for example . in this example , the sale price of digital content data is integrated with the fee of broadcast programs and the resultant amount is charged on the user . in the foregoing , the digital content data distribution systems have been described in which a unit price per unit data volume of digital content data is set , digital content data are sold in a desired data volume , and the user is charged for that data volume . the present invention is also applicable to a product distribution system . first , the concept of a product distribution system to which the present invention is applied will be described with reference to fig1 . this novel concept is that product menu data ( order information ) are accompanied with product costs ( or prices ). in this product distribution system , a product provider 31 which sells products sends product menu data via a network ( or a communication medium ) at the request by a user 3 . at this moment , the product menu data are attached with cost information for each product and the resultant data are transmitted from the product provider 31 to the user 3 via an information communication network ( or a communication medium ) managed by a carrier 2 . if the user 3 received the product menu data and purchases a product from the product menu data , purchase information is transmitted to the product provider 31 from the user 3 via the information communication network managed by the carrier 2 . the product provider 31 transmits the delivery information to a delivery company 32 and instructs the delivery of the product specified by the purchase information . thus , the user 3 can receive the product from the delivery company 32 . the user 3 is charged by a fee collection service company 4 for the purchased product . the price of the product purchased by the user 3 is attached to the product menu data transmitted from the product provider 31 to the user 3 and the fee collection service company 4 detects the product price from the product menu data . having collected the fee from the user 3 , the fee collection service company 4 distributes the collected fee to the carrier 2 , the product provider 31 , and a delivery company 32 in accordance with the agreements concluded between them . it should be noted that various other combinations are practicable in which the carrier 2 also serves as the fee collection service company 4 for example . the following describes an exemplary configuration of the above - mentioned product distribution system with reference to fig1 . with reference to fig1 , components similar to those previously described with fig4 are denoted by the same reference numerals and the description of these components will be skipped . a product server 41 is managed by the product provider 31 and constituted by a content integration block 11 . the other basic configurational parts are the same as those shown in fig4 . as shown in fig4 , the content integration block 11 transmits content ; in this example , however , the content integration block 11 outputs product menu data as content . the product menu data are attached with cost information for each product . to be more specific , the header of a data packet of each product included in the product menu data is written with the cost information of that product and the resultant data packet is transmitted to a transmission block 12 . the cost information about each product in this example is not the fee of that product as the data to be displayed on the display monitor of the user terminal 6 but the information which can be automatically determined as the fee for the product in a management unit 19 . if the management unit 19 can recognize this information , the fee for the product may be described directly or the information indicative of product attributes ( type , quality , etc .) may be described ( in the latter case , a table listing the correlation between attribute information and product fees must be prepared in the management unit 19 ). the transmission block 12 converts the data format of the product menu data attached with the cost information for each product inputted from the content integration block 11 into a data format suitable for an information communication network 14 and transmits the resultant product menu data to a reception block 16 via the information communication network 14 . a gating block 13 of the transmission block 12 acquires the communication information ( attached product cost information , transmitted data volume , sender ( namely the product provider 31 , recipient ( namely , the user 3 ), and , if the recipient purchases a product , the information for identifying the product to be purchased ) about the product menu data received via the information communication network 14 and sends the acquired information to the management unit 19 . a gating block 15 of the reception block 16 acquires the communication information ( attached product cost information , received data volume , sender ( namely the product provider 31 , recipient ( namely , the user 3 ), and , if the recipient purchases a product , the information for identifying the product to be purchased ) about the product menu data received via the information communication network 14 and transmits the acquired information to the management unit 19 . it should be noted that the processes by the gating blocks 13 and 15 for the transmission of the product menu data from the product provider 31 may be executed at the same time as the transmission or reception of the product menu data or the product menu data may be transmitted to the management unit 19 every time the product menu data are updated . the reception block 16 restores the original data format of the product menu data received via the information communication network 14 and outputs the restored product menu data to a content separation block 17 . the content separation block 17 separates the cost information from the product menu data and outputs the resultant product menu data to a content reproduction block 18 . the content reproduction block 18 reproduces the product menu data inputted from the content separation block 17 . the management unit 19 receives the communication information from the gating block 13 of the transmission block 12 and the communication information from the gating block 15 of the reception block 16 . further , the management unit 19 matches the received communication information with the information for identifying the purchased product obtained from the purchase information transmitted from the user terminal 6 to the product provider server 41 to extract the sale price of the product ordered by the user 3 , transmitting the obtained sale price to a charging unit 20 . moreover , the management unit 19 sends the usage information of the product menu data and the charging information about the product ordered by the user to the product provider server 41 and the user terminal 6 . the charging unit 20 charges the user 3 for the purchased product on the basis of the sale price supplied from the management unit 19 . the following describes a sequence of processes for supplying product menu data from the product provider 31 to the user 3 and the amount of money collected from the user 3 is distributed to the carrier 2 , the product provider 31 , and a delivery company 32 , with reference to the flowcharts shown in fig1 through 15 . first , the product providing process by the product provider server 41 managed by the product provider 31 will be described with reference to the flowchart shown in fig1 . in step s 41 , the product provider server 41 determines whether there is a request from the user terminal 6 operated by the user 3 for sending product menu data ( namely , there is an access by the user terminal 6 ). the product provider server 41 repeats this operation until the request is found . if the request is found , the procedure goes to step s 42 . in step s 42 , the product provider server 41 reads the requested product menu data from a predetermined database and adds to the retrieved product menu data the cost information of each product included in the product menu data in the content integration block 11 . in step s 43 , the content integration block 11 outputs the product menu data attached with the cost information to each product in step s 42 to the transmission block 12 . in step s 44 , the user terminal 6 that has received the product menu data determines whether the purchase information for requesting the purchase of product has been transmitted . if the purchase information is found not transmitted , the procedure returns to step s 41 and waits until another request for product menu data comes . if , in step s 44 , the purchase information is found transmitted , then the procedure goes to step s 45 to accept the product specified in the purchase information . in step s 46 , the product provider server 41 transmits the information about the ordered product and the delivery information including the information about purchaser to a delivery management server 42 managed by the delivery company 32 contracted for product delivery in advance . the following describes a communication process for product transaction by the components , the transmission block 12 through the reception block 16 , managed by the carrier 2 with reference to the flowchart shown in fig1 . in step s 61 , the transmission block 12 converts the data format of the product menu data attached with the cost information for each product inputted from the product provider server 41 to the reception block 16 via the information communication network 14 . in step s 62 , the gating block 13 of the transmission block 12 acquires the information ( attached cost information , transmitted data volume , information for identifying sender ( the product provider 31 ), and information for identifying the recipient ( the user 3 )) associated with the transmitted product menu data and sends the acquired information to the management unit 19 . in step s 63 , the reception block 16 restores the original data format of the product menu data supplied via the information communication network 14 . in step s 64 , the gating block 15 of the reception block 16 acquires the information ( attached cost information , received data volume , information for identifying sender ( the product provider 31 ), and information for identifying the recipient ( the user 3 )) associated with the received product menu data and sends the acquired data to the management unit 19 . in step s 65 , the reception block 16 transmits the product menu data restored in step s 63 to the user terminal 6 . in step s 66 , the reception block 16 determines whether the purchase information for requesting product purchase has been transmitted from the user terminal 6 to the product provider server 41 in response to the product menu data transmitted to the user terminal 6 . if the purchase information is found not transmitted , the procedure returns to step s 61 to execute the above - mentioned process when another piece of product menu data comes . if , in step s 66 , the purchase information is found transmitted from the user terminal 6 , then the procedure goes to step s 67 . in step s 67 , the gating block 15 of the reception block 16 extracts , from the received purchase information , the communication information ( information for identifying product to be purchased , product delivery fee , communication fee ( or the information necessary for computing communication fee ), information for identifying sender ( the user 3 ), and information for identifying recipient ( the product provider 31 )) and sends the extracted communication information to the management unit 19 . in step s 68 , the transmission block 12 sends the purchase information supplied from the user terminal 6 to the product provider server 41 . the following describes a product purchasing process to be executed by the content separation block 17 and the content reproduction block 18 constituting the user terminal 6 with reference to the flowchart shown in fig1 . in step s 81 , the user terminal 6 requests the product provider server 41 for product menu data . in response , the product provider server 41 transmits the requested product menu data as described above ( step s 43 of fig1 ). in step s 82 , the user terminal 6 receives at the content separation block 17 the product menu data supplied from the reception block 16 . in step s 83 , the content separation block 17 separates the cost information from each product included in the product menu data received in step s 82 and outputs the resultant product menu data to the content reproduction block 18 . in step s 84 , the content reproduction block 18 reproduces the product menu data removed of the cost information for each product inputted from the content separation block 17 . in step s 85 , from the product menu reproduced in step s 84 , the user terminal 6 determines , instructed by the user 3 , whether a product purchase is requested by the user 3 . if a product purchase is found not requested , then the procedure returns to step s 81 to execute the above - mentioned process again . if , in step s 85 , a product purchase is found requested by the user 3 , then the procedure goes to step s 86 . in step s 86 , the user terminal 6 sends the purchase information ( information for identifying product to be purchased , communication fee ( or information necessary for computing communication fee ), information for identifying sender ( the user 3 ), and information for identifying recipient ( the product provider 31 )) to the product provider server 41 . the following describes a product fee charging process to be executed by the fee collection server 7 managed by the fee collection service company 4 with reference to the flowchart shown in fig1 . in step s 101 , the management unit 19 receives the communication information supplied from the gating block 13 of the transmission block 12 and the communication information supplied from the gating block 15 of the reception block 16 . then , the management unit 19 matches the received communication information with the communication information for identifying purchase product obtained at the gating blocks 13 and 15 obtained from the purchase information transmitted from the user terminal 6 to the product provider server 41 . at the same time , the communication fee is computed as required . the sale price and the delivery fee are integrated with the communication fee . in step s 102 , the management unit 19 sends the communication fee computed ( or synthesized ) in step s 101 to the charging unit 20 . in step 5103 , the management unit 19 sends the product charging information to the user terminal 6 and the product provider server 33 . in step s 104 , the charging unit 20 charges the user 3 on the basis of the communication fee obtained in step s 102 . in step s 105 , the charging unit 20 distributes the product fee collected from the user 3 in step s 104 to the carrier 2 ( the communication fee before it is integrated with the content fee ), the product provider 31 ( the sale price ), and the delivery company 32 ( the delivery fee ). in the above - described examples , each transaction in which the user 3 purchases a product is established when the user 3 transmits the purchase information about the product to be purchased via the information communication network 14 on the basis of the product menu data supplied from the product provider server 41 . however , the product purchase form is not restricted to those described above . for example , if agreements have been concluded between the user 3 and the product provider 31 to the effect that a product is delivered to the user 3 on a certain specified day every month , the fee collection service company 4 can execute a charging process on the basis of the information acquired from the gating blocks 13 and 15 by causing the product provider 31 to transmit the product information including the cost information about that product to the user 3 . in this case , the user 3 need not transmit the purchase information to the product provider 31 via the information communication network 14 every time in response to the information supplied from the product provider 31 . in this case , the delivery company 32 may only deliver the purchased product to the user 3 on a day specified by the product provider 31 . it should be noted that the present invention is applicable to any services that sell and / or buy digital content data through a given communication infrastructure . the concentrated management of all services that sell and / or buy digital content data through a given communication infrastructure enhances the convenience for the user 3 because he may make payments only to the fee collection service company 4 . in addition , the user 3 need not execute the followings which are required with the prior - art . first , the user 3 is not required to enter certain certificates and personal information . second , the user 3 need not download or install new software into the terminal device . third , the user 3 need not pay in advance ( for example , prepaid fee , purchase of electronic money , etc .). fourth , the user 3 need not register with the carrier 2 beforehand . fifth , the user 3 can acquire economic safety and security that the payment of fees is established by the establishment of communication . on the other hand , because the present invention allows the information provider 1 ( the product provider 31 ) and the carrier 2 to secure the collection of the content fee and the communication fee respectively , the present invention enhances the convenience of the sides of these enterprises . in addition , when the charging is made depending on data volume , the present invention allows the information provider 1 ( the product provider 31 ) to set content costs as desired regardless of the data volume of digital content data for sale . in the above - mentioned preferred embodiments of the invention , the cost information per unit data volume is attached to each unit data of content . it will be apparent to those skilled in the art that the cost information per unit data volume may be attached to a group of plural pieces of unit data . the price of digital content data is computed by multiplying a used or received data volume by the information cost per unit data volume . in the above - mentioned preferred embodiments of the invention , the transmission information associated with digital content data is sent from the transmission block to the management unit and the reception information associated with the received digital content data is sent from the reception block to the management unit . the following alternatives can also be practiced . namely , a server for managing data transmission arranged on a communication route over which data are transmitted from a transmission block to a reception block may send the transmission information associated with this transmission to the management unit . or a server for managing data transmission arranged halfway on a communication route over which data are transmitted from a transmission block to a reception block may send the reception information associated with this reception to the management unit . or the server near the transmission block on the communication route may send the transmission information about transmission to the management unit and the server near the reception block arranged on the transmission route may send the reception information about reception to the management unit . consequently , the management unit is given the transmission information and the reception information from either the transmission block and the reception block , one of these information items from the server , or both from the server . namely , the management unit is supplied with the transmission information and reception information about digital content data from a predetermined point on the communication route between the transmission block and the reception block inclusive . the above - mentioned sequences of processes can be executed by hardware or software . the execution by software is supported by a computer in which the programs constituting the software are installed in a dedicated hardware device beforehand or by a general - purpose personal computer capable of executing various capabilities in which these programs are installed from the program storage medium . fig1 illustrates an exemplary configuration of a personal computer in which the software for executing the above - mentioned sequence of processes is installed . the personal computer incorporates a cpu ( central processing unit ) 101 . the cpu 101 is connected to an input / output interface 105 via a bus 104 . the input / output interface is connected to an input block 106 composed of such input devices as keyboard and mouse , an output block 107 for outputting a processing result , for example , an audio signal , a display block 108 constituted by a display monitor for displaying an image of a processing result , a storage block 109 constituted by a hard disk drive for storing programs and various data , a communication block 110 constituted by a modem for communicating data via a lan ( local area network ) or the internet , and a drive 111 which executes a data read / write operation on a magnetic disc ( including floppy disc ) 112 , an optical disc ( including cd - rom ( compact disc - read only memory ) 113 and dvd ( digital versatile disc ) 114 , a magneto - optical disc ( including md ( mini disc ), or a semiconductor memory 115 . the bus 104 is connected to a rom ( read only memory ) 102 and a ram ( random access memory ) 103 . the software for executing the sequence of processes is supplied to the personal computer as stored in one of the magnetic disc 112 through the semiconductor memory 115 . the supplied software is read by the drive 111 and installed in the hard disk drive incorporated in the storage block 109 . the agent program stored in the storage block 109 is loaded from the storage block 109 into the ram 102 for execution as instructed by the cpu 101 on the basis of a command inputted from the input block 106 by the user . it should be noted that the steps describing the programs to be stored in the program storage medium are not only executed in a time - dependent manner in the order described , but also in parallel or in a discrete manner . it should also be noted that the system as used herein denotes an entire apparatus constituted by a plurality of component units . while the preferred embodiments of the present invention have been described using specific terms , such description is for illustrative purposes only , and it is to be understood that changes and variations may be made without departing from the spirit or scope of the appended claims .