text: preferred embodiments of the present invention will be hereinafter described in detail with reference to the drawings . fig1 is a rear view showing , with a back cover removed , the rear side of a camera arranged as a first embodiment of the invention . the illustration of fig1 includes a camera body 1 , a cartridge chamber 2 , a fork 3 , a spool chamber 4 , a film take - up spool 5 and an aperture 6 which is provided in the camera for exposing a film to light . a photo - reflector 7 is disposed in an upper left part on the rear side as viewed in fig7 and is arranged to detect a perforation of the film between a frame located currently in a photographing position and the next frame . a magnetic head 8 is arranged to come into pressed contact with a magnetic layer of the film and to magnetically record or reproduce information into or from the magnetic layer of the film . fig2 shows in a block diagram the circuit arrangement of the above - stated camera . referring to fig2 a control circuit 50 is arranged to control various circuits of the camera and is composed of a microprocessor , etc . a battery 51 is arranged as a power source . a switch 52 is arranged to be turned on by the first stroke of a shutter release button . a release switch 53 is arranged to be turned on by the second stroke of the shutter release button . a light measuring circuit 54 is arranged to measure the luminance of an object to be photographed . a distance measuring circuit 55 is arranged to measure a distance to the object . an af ( automatic focusing ) driving circuit 56 is arranged to adjust the focus of a photo - taking lens ( not shown ) on the basis of information on the distance measured by the distance measuring circuit 55 . a shutter control circuit 57 is arranged to control the opening and closing actions of a shutter . a motor driving circuit 58 is arranged to drive a film transport motor 59 . a storage circuit 60 is composed of a nonvolatile storage element such as an eeprom , etc . a timer 61 is provided for the control circuit 50 . a magnetic recording and reproducing circuit 62 is arranged as a magnetic processing circuit to record and reproduce information on and from the film . a bar code reading part 64 is arranged to read from a bar code disk 63 of a cartridge a number of film frames and a state of use of the film recorded in bar codes on the bar code disk 63 . a display circuit 65 is arranged to display a shutter time value ( tv ) and an aperture value ( av ) and also to provide a warning display relative to an error of the magnetic recording and reproducing circuit 62 . a magnetic head driving circuit 66 is arranged to cause the magnetic head 8 to come into contact with the surface of the film and to retract the head 8 from the film surface . a film rewinding mode setting switch 67 is arranged , for example , to bring about an automatic rewinding ( abbreviated to a . rew ) mode when it is in an on - state and a manual rewinding ( abbreviated to m . rew ) mode when it is in an off - state . there is provided a manual rewinding start button 68 for manual film rewinding . fig3 is a flow chart showing an operation of the control circuit 50 with the control circuit 50 assumed to be composed of a microprocessor . referring to fig3 when the camera is loaded with a film cartridge at a step 110 , the flow of operation proceeds to a step 120 . at the step 120 , the film transport motor 59 is driven to rotate in the direction of film rewinding . this rotation causes a spool disposed within the film cartridge to rotate . at a step 130 , the control circuit 50 reads from the bar code disk 63 of the film cartridge the information on a total number of photographable frames and the state of use of the film cartridge recorded on the bar code disk 63 . at steps 140 and 150 , the total number of photographable frames and the state of use of the film cartridge ( an unused state , a partially used state or a used state ) are stored . the bar code disk 63 on the film cartridge is arranged such that , if the film cartridge has not been used in its initial stage after loading it on the camera , the initial code part 63a of the bar code disk 63 ( see fig2 ) is located at a first position relative to a reading part which is composed of a photo - coupler . in the case of a film cartridge in which all film frames have been used , i . e ., exposed , the initial code part 63a is located at a second position which differs from the first position relative to the reading part . further , if the film cartridge has its film rewound into it in a partially exposed state , i . e ., a partially used state , the initial code part 63a is located at a third position which differs from the first and second positions relative to the reading part in its initial stage after loading . such being the arrangement , the state of use of the film cartridge currently loaded into the camera can be found by detecting the initial position of the initial code part 63a by sensing the time required to detect the initial code part 63a in reading the information at the step 130 . at a step 160 , a driving action on the film transport motor 59 is brought to a stop . at a step 170 , a check is made for the state of use of the film cartridge currently loaded into the camera on the basis of information on the state of use of the film cartridge stored at the above - stated step 150 . if the film cartridge is found to be in the used state , the flow of operation proceeds from the step 170 to a step 180 . at the step 180 , the display circuit 65 is caused to provide a warning display , and the flow of operation comes to an end without winding the film . if the film cartridge is found to be in the unused state at the step 170 , the flow proceeds from the step 170 to a step 190 . at the step 190 , a film winding action begins by causing the film transport motor 59 to make a normal rotation . at the next step 200 , the output of the photo - reflector 7 is checked to find if the leader part of the film sent out from the film cartridge has passed the position of the photo - reflector 7 . if so , the flow proceeds to a step 210 . at the step 210 , the output of the photo - reflector 7 is checked to find if a perforation of the film has been detected . if so , the flow proceeds to a step 220 . at the step 220 , the driving action on the film transport motor 59 is brought to a stop . at a step 221 , a frame number is set at &# 34 ; 1 &# 34 ;. the value &# 34 ; 1 &# 34 ; is displayed by a display member such as an lcd of the camera . the flow then proceeds to a step 410 and subsequent steps shown in fig5 . as shown in fig1 , in the film to be used by the camera , two perforations are provided for each frame of the film . the flow of operation proceeds to the step 220 when a perforation &# 34 ; a &# 34 ; located at the leading point of a frame is detected at the step 210 . if the film cartridge is found at the step 170 to be in the partially used state , the flow proceeds from the step 170 to a step 230 . at the step 230 , the film winding action is allowed to begin by causing the film transport motor 59 to make a normal rotation . at a step 240 , the output of the photo - reflector 7 is checked to find if the leader part of the film sent out from the film cartridge has passed the position of the photo - reflector 7 . after that , the flow proceeds to a step 250 . at the step 250 , the magnetic head driving circuit 66 is caused to bring the magnetic head 8 into contact with the surface of the film . at a step 260 , the photo - reflector 7 is checked to find if the leading perforation &# 34 ; a &# 34 ; has been detected . if so , the flow proceeds to a step 265 to set the frame number at &# 34 ; 0 &# 34 ;. however , the frame number is not displayed at this point of time . at a step 270 , magnetic signals recorded on the film are reproduced . at a step 280 , the number of pulses of data , i . e ., the number of reproduced signals , are counted until the leading perforation &# 34 ; a &# 34 ; of the next frame is detected . when the next perforation &# 34 ; a &# 34 ; is detected , the flow proceeds to a step 290 . at the step 290 , the number of reproduced signals is read and the value thus read is set as n . at the next step 300 , the frame number is incremented by one and the new frame number is displayed . at a step 310 , a check is made to find if the frame number has reached the ( specified ) number of photographable frames read at the step 140 . if so , the flow proceeds to a step 635 , which is shown in fig6 and is provided for film rewinding . if the frame number is found not to have reached the specified ( maximum ) number of photographable frames at the step 310 , the flow of operation proceeds to a step 320 . at the step 320 , a check is made to find if the reproduced number of signals n is equal to or greater than a predetermined value t . if so , the frame is judged to be an exposed frame , and the flow returns to the step 270 . if not , the frame is judged to be an unexposed frame , and the flow proceeds to a step 330 . at the step 330 , the film transport motor 59 is brought to a stop to end film winding . the flow then proceeds to a step 340 which is shown in fig4 . at the step 340 , the film transport motor 59 is caused to make a reverse rotation to start transporting the film in the direction of rewinding . at a step 360 , a check is made for the next perforation ( a leading perforation &# 34 ; a &# 34 ; of a frame preceding the current frame by one frame portion of film ). upon detection of the next perforation , the flow proceeds to a step 370 to stop the motor 59 from rotating . in other words , the film is thus rewound here to the extent of one frame amount . at a step 390 , the information on the state of use of the film cartridge stored at the step 150 is checked to find if the film cartridge is in the partially used state . if so , the flow proceeds to a step 400 to store information on the number of exposed frames contained in the partially used film cartridge . a nonvolatile storage element such as an eeprom is used for storing it . the value stored at the step 400 is obtained by subtracting &# 34 ; 1 &# 34 ; from the count value obtained at the step 300 . if the film cartridge is found not to be in the partially used state , i . e ., it is in a totally unexposed state in this instance , the flow of operation skips the storing routine of the step 400 . after the step 390 or 400 , the flow proceeds to a step 410 which is shown in fig5 . referring to fig5 at the step 410 , a check is made to find if the manual rewinding start button ( m . rew ) 68 has been turned on . if so , the flow proceeds to a step 635 provided for a rewinding routine as shown in fig6 . if not , the flow proceeds to a step 510 . at the step 510 , a check is made for the state of the switch 52 ( sw1 ) to find if the switch 52 is turned on by the first stroke of the shutter release button of the camera . if so , the flow proceeds to a step 520 . at the step 520 , a light measuring action is performed for photographing . a shutter time value and an aperture value are decided according to light thus measured . at a step 530 , a distance measuring action is performed and automatic focus adjustment is carried out in a known manner . at a step 540 , a check is made for the state of the switch 53 ( sw2 ) to find if the switch 53 is turned on by the second stroke of the shutter release button . if so , the flow proceeds to a step 540 &# 39 ;. if not , the flow returns to the routine of the step 510 . at the step 540 &# 39 ;, the magnetic head 8 is retracted from the film surface , and the flow proceeds to a step 550 . at the step 550 , the film is exposed to light by controlling the shutter on the basis of the shutter time decided and by controlling a diaphragm on the basis of the aperture value decided as mentioned above . after completion of the exposure , the flow proceeds to a step 560 . at the step 560 , information on the photographing conditions for the current frame , such as the shutter time , the aperture value , the luminance of an object to be photographed , etc ., is stored in a nonvolatile storage element or the like together with the frame number , which is a count number obtained by a counter . at the next step 570 , film winding is caused to begin by causing the film transport motor 59 to make a normal rotation . at a step 590 , a check is made for detection by the photo - reflector 7 of the leading perforation &# 34 ; a &# 34 ; of the next frame . when the perforation is detected , the flow proceeds to a step 600 . at the step 600 , the process of film winding is brought to an end by stopping the film transport motor 59 from being driven . at the next step 620 , the frame number is incremented by one . at a step 630 , a check is made to find if the frame number counted has exceeded the specified number of photographable frames stored at the step 140 . if not , the flow proceeds to a step 633 to display the frame number , and then returns to the step 510 to carry on the photographing actions . if the frame number is found at the step 630 to have exceeded the specified number of photographable frames , the flow proceeds to a step 631 . at the step 631 , a check is made for the state of the film rewinding mode setting switch 67 to find if the current film rewinding mode is the automatic rewinding ( a . rew ) mode . if so , the flow proceeds to a step 635 which is shown in fig6 . in the event of the manual rewinding start mode , the flow proceeds to a step 632 to wait for turning - on of the m . rew switch 68 . when this switch 68 is turned on , the flow proceeds to the step 635 . at the step 635 , the film is caused to be transported in the direction of film rewinding by causing the film transport motor 59 to make a reverse rotation . at a step 636 , the magnetic head 8 is brought into contact with the film . at a step 636 &# 39 ;, the count value of the counter is decremented by one . the flow then proceeds to a step 637 . at the step 637 , a check is made , on the basis of information stored at the step 150 , to find if the film cartridge has been in the partially used state when the camera is loaded with it . if so , the flow proceeds to a step 638 . at the step 638 , a check is made to find if the current frame number ( the count value of the counter ) has reached the number of exposed frames stored at the step 400 . if not , the flow proceeds to a step 639 . at the step 639 , information which is stored at the step 560 for the frame of the frame number ( count value of the counter ) is written into the magnetic recording layer of the film in accordance with a predetermined format . if the film cartridge is found at the step 637 to have been in the totally unexposed state when it is loaded , the flow proceeds immediately to the step 639 to execute the magnetic writing process , skipping the check to be made at the step 638 . if the frame number is found at the step 638 to have reached the number of exposed frames , the flow proceeds to a step 650 without executing the magnetic writing step 639 . at the step 650 , a check is made for detection of the leading perforation &# 34 ; a &# 34 ; of each frame to find if one frame amount of the film has been transported . if so , the flow proceeds to a step 660 . at the step 660 , the count value of the counter is decremented by one and the value thus obtained is displayed . at the next step 670 , a check is made to find if the count value of the counter is &# 34 ; 0 &# 34 ;. if not , the flow returns to the step 637 . if so , the flow proceeds to a step 680 . at the step 680 , a timer of a predetermined time is set . this timer is provided for causing the flow to wait for a predetermined period of time necessary before the film is completely wound into the film cartridge . after the lapse of the predetermined time , the flow proceeds to a step 685 to have the magnetic head 8 retracted from the film . at the next step 690 , the initial code part 63a of the bar code disk 63 is set in a position according to the current state of use of the film cartridge , which is one of the three states including the unexposed ( unused ) state , the partially exposed ( partially used ) state and the totally exposed ( used ) state . at the next step 700 , the process of film rewinding is brought to an end by stopping the film transport motor 59 from rotating . at a step 710 , the film cartridge is taken out , and the sequence of processes described comes to an end . further , when the number of exposed frames is found to have reached the maximum number of frames at the step 310 , with a film cartridge loaded in the partially exposed state , or when the manual film rewinding start button 68 is found to be turned on at the step 410 , the flow of operation immediately enters into the film rewinding start routine of the step 635 . fig7 to 10 are flow charts showing flows of operation of a camera according to a second embodiment of the invention . in these flow charts , the steps which are to be executed in the same manner as the steps shown in fig3 to 6 are indicated by the same step numbers as in fig3 to 6 . the second embodiment is arranged in the same manner as the first embodiment described above , except in the following points . in the second embodiment , when the camera is loaded with a partially exposed film cartridge , information on the position of a leading frame of unexposed frames is stored at the step 401 of fig8 . in rewinding the film , a check is made at a step 638b of fig1 to find if the film frame rewinding position has passed the position of the leading unexposed frame and , if so , the control circuit 50 inhibits information writing . the film rewinding arrangement adapted for a case where the camera is loaded with a partially exposed film cartridge also differs from the arrangement of the first embodiment described above . the following description of the operation of the second embodiment covers mainly the points where the second embodiment differs from the first embodiment . referring to fig7 in a case where the camera is loaded with a partially exposed film cartridge , steps 110 to 170 and steps 230 to 260 are executed , so that the leading part of the first frame is thus fetched to a predetermined position by finding the leading perforation &# 34 ; a &# 34 ; of the first frame . at a step 266 , the frame number is set at &# 34 ; 1 &# 34 ; in the frame counter . at a step 267 , the frame number is displayed . after that , steps 270 to 290 are executed to reproduce the magnetic signals of the frame . then , with a one - frame winding action performed , the count value of the counter is incremented by one at the step 301 . steps 310 and 320 are executed to find if the frame for which the magnetic signals are reproduced is an exposed frame . if so , the flow proceeds to the step 267 to display the frame number of the frame currently wound up . during the flow of these processes , a leading unexposed frame is wound up , and , when the frame is judged to be an unexposed frame through the signals reproduced from the frame , the flow proceeds to the step 330 . in this instance , a frame located next to the leading unexposed frame is at the aperture position and the count value of the counter also represents the frame number of the next frame . however , since the step 267 for the frame number display is not executed when the leading unexposed frame is judged to be an unexposed frame , the frame number on display is a number less by one than the counted frame number and thus indicates the frame number of the leading unexposed frame . after that , steps 340 to 370 of fig8 are executed to rewind the film by one frame amount . the leading unexposed frame is thus moved to the aperture position . the frame number of the frame thus brought to the aperture position then comes to coincide with the frame number on display . at a step 401 , the frame number of the leading unexposed frame detected is stored . the frame number thus stored is a value less by one than the frame number counted by the counter immediately before the step 340 . at a step 402 , the count value of the counter is decremented by one to make it coincide with the frame number of the frame currently located in the aperture position . after the step 402 , the flow proceeds to execute steps 410 to 632 which are shown in fig9 . through these steps 410 to 632 , each frame is exposed to light and information relative to these frames are stored . after all frames are exposed to light , the flow comes to execute steps 635 to 710 which are shown in fig1 . in the case of the second embodiment , at a step 638b , the count value of the counter becomes less than the frame number of the leading unexposed frame , i . e ., a leader position of unexposed frames , stored at the step 401 . then , the stored information is magnetically recorded in rewinding each of frames until a leading frame among the unexposed frames comes to the aperture position . further , this embodiment is arranged to make the frame number display in the manner described above on the assumption that the camera is arranged to perform the magnetic writing at the time of film rewinding when the camera is loaded with a partially exposed film cartridge . however , the same method of making the frame number display according to the invention applies also to a camera arranged to perform the magnetic writing at the time of winding the film , instead of at the time of rewinding .