an embodiment according to the present invention will now be described in detail with reference to the drawings . fig1 is a block diagram illustrating a facsimile apparatus according to an embodiment of the present invention . as shown in fig1 the apparatus includes a main controller 1 comprising a single - chip microcomputer which includes a cpu la , a rom 1b for a program memory , and a ram 1c for a working memory . the main controller 1 administers overall control of the embodiment in accordance with a control program stored in the rom 1b and illustrated in fig3 . connected to the main controller 1 are a reader 2 comprising an image scanner or the like , which includes a ccd image sensor , an original - document conveyance mechanism , etc ., a recorder 3 constituted by a thermal printer , an ink - jet printer or a laser - beam printer , by way of example , a communication controller 4 comprising a modem , a network control unit ncu , etc ., a control panel 5 comprising a keyboard and the like , or a display unit 6 comprising an lcd or the like . a line 10 is connected at one end to the communication controller 4 and at its other end to another facsimile apparatus or the like via a public telephone network , etc . a control - data memory 20 comprises a ram or the like for storing various types of control data , described below , and an image - information memory 30 comprises a ram or the like for temporarily storing image information to be transmitted , or image information that has been received , under the control of the main controller 1 . the image - information 30 , which is constituted by a ram or the like , is one example of a storage medium having a high storage speed . also connected to the main controller 1 is a floppy - disk drive ( hereinafter referred to as an &# 34 ; fdd &# 34 ;) 40 for loading a floppy disk ( hereinafter referred to as an &# 34 ; fd &# 34 ;) 41 loaded and unloaded at will . the fd 41 functions as an external storage device in this embodiment and is one example of a storage medium having a low storage speed . the image - information memory 30 has a memory area which is partitioned into a plurality of memory blocks in storage units of the same size as that of the fd 41 , e . g ., in units 512 bytes . the stored image information is transferred , in block form , to the fd 41 every memory cycle by the main controller 1 . the control - data memory 20 includes a starting - address pointer sap which points out an address of the image - information memory 30 . the main controller 1 stores image information , which has arrived from the communication controller 4 , in the image - information memory 30 from the address designated by the pointer sap toward a higher - order address . at the end of storage of the image information , the address value of the beginning of the memory block following the last memory block in which the above - mentioned image information has been stored is stored in the starting - address pointer sap by the main controller 1 . in other words , the starting - address pointer sap always points toward the starting address of the starting memory block of the image - information memory at which the storage of the image information is to begin . in addition to having the starting - address pointer sap , the control - data memory 20 includes an end - address pointer eap , a transfer pointer tp , a storage pointer sp , a block pointer bp , and an error flag e - flag , etc . the most significant address of the image - information memory 30 at which image information is capable of being stored in the fd 41 currently loaded in the fdd 40 is stored in the end - address pointer eap by the main controller 1 . in other words , if a memory block of the image - information memory 30 is transferred to the fd 41 , which is currently loaded in the fdd 40 , beyond the address designated by the end - address pointer eap , the blank memory of fd 41 will run out and , as a result , an image - information storage error will be generated . the transfer pointer tp points to the beginning address of a memory block group in the process of being transferred , or awaiting such transfer , from the image - information memory 30 to the fd 41 . at the end of transfer of the memory block group , the beginning address of the least significant blank memory block is stored in the transfer pointer tp . the storage pointer sp , which is an address pointer used during image - information storage processing by the main controller 1 , points to the address of the image - information memory 30 at which the processing for storing image information is in progress . the block pointer bp , which is an address pointer used during image - information transfer processing by the main controller 1 , points to the address of the image - information memory 30 , at which the processing for transferring image information is in progress , by an offset address from the transfer pointer tp . the error flag e - flag is set / reset by the main controller 1 . the flag is set when processing for storing image information ends in an error , and is reset by the main controller 1 when error processing by the main controller 1 ends . fig2 is a diagram showing an example of the relationship between the arrangement of the image - information memory 30 and the address pointers . the image - information memory 30 shown in fig2 includes blocks 0 to 3 for which the transfer of image information to the fd 41 has already been completed , a block 4 from which image information is currently being transferred to the fd 41 , blocks 5 and 6 for which storage of image information has been completed , blocks 7 and 8 for which image information is currently being stored , and blocks 9 to n , which are blank memory blocks . blank memory size fs of fd41 is equal to the memory size of blocks 4 to n - 2 . in fig2 bs represents the memory block size of the image - information memory 30 , a31 the least significant address of the image - information memory 30 , and a39 the most significant address of the image - information memory 30 . in the description and drawings to follow , the beginning address of the least significant blank memory block of the image - information memory 30 is represented by a35 . the flow of processing for storing and transferring image information according to this embodiment will now be described . fig3 is a flowchart for describing the flow of processing performed by the main controller 1 . in particular , special emphasis is given to processing relating to the storage and transfer of image information by the main controller 1 . when the power supply is turned on , the main controller 1 clears the control - data memory 20 and initializes the pointers and flag at step s31 in fig3 . next , at step s32 , the main controller 1 investigates the signal from the communication controller 4 and determines whether communication with another facsimile apparatus has started . if the main controller 1 has determined that communication with another facsimile apparatus has started , the program proceeds to step s33 . otherwise , the program proceeds to step s39 . the main controller 1 determines at step s33 whether the communication that has started is for transmission or reception of image information . the program proceeds to step s34 in case of transmission or to step s35 in case of reception . step s34 is processing which the main controller 1 executes to transmit image information . since this is processing not directly related to the present invention , a detailed description thereof is omitted . when the main controller 1 finishes executing the processing of step s34 , the program returns to step s32 . when it is determined at steps s32 and s33 that communication has started and that image information is to be received , the main controller 1 executes image - information storage processing , the details of which are described below , at step s35 , and investigates the error flag e - flag at step s36 . if the e - flag is found to be &# 34 ; 1 &# 34 ;, the program proceeds to step s37 , where communication - suspension processing is executed to suspend communication . this is followed by step s38 , at which the e - flag is reset to &# 34 ; 0 &# 34 ;. when the main controller 1 finishes the processing of step s36 or step s38 , the program returns to step s32 . if it is found at step s32 that communication has not started , the main controller 1 executes image - information transfer processing , the details of which are described later , at step s39 . when the processing of step s39 ends , the program returns to step s32 . in this embodiment , the main controller 1 repeatedly executes the processing from step s32 onward until the power supply is turned off . the processing for storing image information according to this embodiment will now be described . fig4 is a flowchart illustrating the processing executed by the main controller 1 to store image information . in the drawing and description to follow , a . sub . ( sap ), by way of example , represents an address of the image - information memory 30 pointed to by the starting - address pointer sap . the same is true for the other pointers as well . at step s1 of fig4 the main controller 1 acquires the memory size fs of the blank memory area in the currently loaded fd 41 via the fdd 40 . if the fd 41 is a floppy disk formatted in the ms - dos ® operating system , by way of example , the blank memory size fs of fd 41 can be acquired from a file allocation table fat stored on the fd . next , at step s4 , the main controller 1 compares the storage - address pointer sp and the end - address pointer eap . it is confirmed through this processing that blank memory in the fd 41 will not run out if the image information to be stored from this point onward is transferred to the fd 41 . in other words , if sp ≦ eap holds , the main controller 1 judges that blank memory in the fd 41 will not run out , and the program proceeds to step s5 . if sp & gt ; eap holds , the main controller 1 judges that blank memory in the fd 41 will run out , and the program proceeds to step s11 . at this step , the error flag e - flag is set to &# 34 ; 1 &# 34 ;. then , at step s12 , an error warning is issued , after which the processing for storing the image information is terminated . at step s5 , the main controller 1 compares the storage address sp with the most significant address a39 of the image - information memory 30 , thereby confirming that blank memory in the image - information memory 30 will not run out owing to the image information to be stored from this point onward . that is , the main controller 1 causes the program to proceed to step s6 if sp ≦ a39 holds and to step s11 if sp & gt ; a39 holds . at step s11 , the error flag e - flag is set to &# 34 ; 1 &# 34 ;. the error warning is then issued at step s12 , after which the processing for storing the image information is terminated . at step s6 , the main controller 1 stores one byte of image information in the image - information 30 at an address a . sub . ( sp ) pointed to by the storage pointer sp . this is followed by step s7 , at which the storage pointer sp is incremented , and then by step s8 , at which it is determined whether there is still image information to be stored . the program returns to step s4 if there is still image information to be stored , or proceeds to step s9 if there is no further image information . in case of a g3 facsimile , for example , the determination as to whether or not there is image information to store is made by the main controller 1 based upon an eop ( end - of - procedures ) signal contained in post - message commands in accordance with ccitt recommendation t . 30 . in other words , when the eop signal is received , the main controller 1 judges that there is no longer any image information to be stored . until the eop signal is received , the main controller 1 judges that image information to be stored still remains . at step s9 , the main controller 1 stores , in the starting - address pointer sap , the beginning address of the memory block that follows the memory block which includes the address pointed to by the storage pointer sp . as a result , processing for storing image information is terminated after the starting - address pointer sap is updated . more specifically , in the above - described processing for storing image information , the main controller 1 successively determines whether the transfer of image information to the fd 41 and the storage of image information in the image - information memory 30 are possible . if these are possible , then the storage of image information in the image - information memory 30 is continued ; otherwise , the error flag e - flag is set and the storage of the image information is suspended . in the case where storage of the image information is suspended , the starting - address pointer sap is not updated but maintains the same value that prevailed when processing for storing the image information started . the error warning at step s12 is implemented as by displaying an error message on the display unit 6 . however , the error - message display can be combined with a warning tone produced by a buzzer or the like . fig5 is a flowchart illustrating processing which the main controller 1 executes to transfer image information . at step s21 in fig5 the main controller 1 acquires the memory size fs of the blank memory area in the currently loaded fd 41 via the fdd 40 . if the fd 41 has been ejected from the fdd 40 when the processing of step s21 is executed , then , by way of example , the fdd 40 sends back a signal indicative of fs = 0 to the main controller at step s21 . next , at step s22 , the main controller 1 compares the memory size fs obtained at step s21 with the memory block size bs , thereby confirming whether the blank memory area of the fd 41 is greater than the memory block size bs . in other words , the main controller 1 causes the program to proceed to step s23 if fs ≧ bs holds or to step s30 if fs & lt ; bs holds . an error warning is issued at step s30 , after which the processing for transferring the image information is terminated . the error warning at step s30 is implemented as by displaying an error message on the display unit 6 . however , the error - message display can be combined with a warning tone produced by a buzzer or the like . following step s22 , the main controller 1 initializes the block pointer bp to 0 at step s23 , transfers one byte of image information at address a . sub . ( tp + bp ) of the image - information memory 30 to fd 41 at step s24 , and increments the block pointer bp at step s25 . then , at step s26 , the main controller 1 compares the block pointer bp with the block size bs , thereby verifying whether the transfer of one memory block has ended or not . that is , the program causes the program to proceed to step s27 if bp ≧ bs holds or to return to step s24 , where transfer of the image information is continued , if bp & lt ; bs holds . the main controller 1 adds the memory block size bs to the value of the transfer pointer tp at step s27 , thereby updating the transfer pointer tp , and compares the transfer pointer tp with the starting - address pointer sap at step s28 if tp & lt ; sap is found to hold at step s28 , processing for transferring the image information is terminated . if tp ≧ sap holds , the program proceeds to step s29 . in other words , if tp ≧ sap holds at step s28 , the main controller 1 judges that all of the image information stored in the image - information memory 30 has been transferred to the fd 41 , stores the beginning address a35 of the least significant blank memory block of the image - information memory 30 in the transfer pointer tp and starting - address pointer sap , and terminates the image - information transfer processing after updating the transfer pointer tp and starting - address pointer sap . in the above description , and in fig2 it is explained that the processing operation for storing image information and the processing operation for transferring image information are executed alternately by the main controller 1 . however , if the main controller 1 used is capable of multi - task processing , then it will be possible for the image - information storage processing and the image - information transfer processing to be executed simultaneously . in accordance with the present invention , as described above , the blank memory of the fd 41 does not run out during the transfer of image information from the image - information memory 30 ( the first storage medium ) to the fd 41 ( the second storage medium ). as a result , the image information stored in the image - information memory 30 is transferred to the fd 41 with assurance . this enhances the reliability of the facsimile apparatus and provides the user with a sense of security . as many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof , it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims .