Abstract:
Disclosed is an image forming apparatus having a memory recall function and a serial number printing function. In a case where a user selects the both function after printing of a specific print job, a controller of the image forming apparatus automatically calculates a starting serial number which is to be added to a first sets of prints of the next job.

Description:
This application is based on application No. HEI 09-312138 filed in Japan, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to an image forming apparatus and its controller, and more particularly, to (i) an image forming apparatus that forms one or more sets of images while saving data for one set of images in memory and that forms one or more sets of images using the stored image data, and (ii) a controller that is used in said image forming apparatus. 
     2. Description of the Related Art 
     Various technologies have conventionally been added to image forming apparatuses to enable the user to efficiently print or make copies of images and make it easy for the user to manage the printed images. 
     Using the technology disclosed in Japanese Laid-Open Patent Application HEI 5-122477, the image data for which printing has been completed is saved in an image memory, and this image data is read and printing is performed once again through a prescribed operation. This technology pertains to a function to (i) record and save image data for an image for which printing has been completed and (ii) perform printing once again by reading this image data. (In the present specification, this function and a mode using this function are hereinafter termed the memory recall function and the memory recall mode, respectively). 
     Separate from the technology introduced above, an image forming apparatus having a function to allocate a management number to each set of copies when a set of images is printed in one print job is also known. (In the present specification, this function and a mode using this function are hereinafter termed the serial number printing function and the serial number printing mode, respectively.) Using this serial number printing function, the user can easily determine the number of sets of images printed. 
     However, there are situations in which the user wishes to allocate, while using the memory recall function, a number to a set of copies that is sequential to the last number that was allocated to the prior set of printed images previously printed. An image forming apparatus having the memory recall function and the serial number printing function is already known. However, in the conventional image forming apparatus having these functions, the user must manually input a management number that is sequential to the last management number of the previous job so that the input management number will be the starting control number for the current job, after confirming the number of sets of images that were previously printed with control numbers. 
     This type of manual operation is inconvenient for the user, and moreover, when manual inputting is performed, there is a possibility that an image having the same management number may be printed due to mistaken operation by the user, and accurate management may not be achieved. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to resolve these problems. Its object is to provide an image forming apparatus and a controller for an image forming apparatus that (i) eliminate the need for an operation that is inconvenient for the user and (ii) can accurately manage the number of images formed. 
     For example, the present invention pertains to a controller for an image forming apparatus, which comprises a processor which automatically determines a starting serial number which is to be given to the first set of prints of a first print job in a case where a memory recall function and a serial number printing function are set, the starting serial number being sequential to the last serial number given to a second print job previously executed. 
     Image forming apparatus to which the controller having the above mentioned construction is applied may be a printer which makes printed materials based on image data inputted from external host computer, or may be a copier which reads document images, generates image data of the document images, and makes printed materials based on image data of documents. 
     In the image forming apparatus in which the controller having the above mentioned construction is applied, the user need not manually input the starting serial number when performing serial number printing for a job using the memory recall function. In addition, since the starting serial number is automatically determined, the number of sets of printed images can be accurately managed. 
     In the image forming apparatus in which the controller having this construction is applied, the serial numbers used in the serial number printing mode may be printed on the first page only of each set of printed images. 
     These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings which illustrate a specific embodiment of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view showing the construction of the digital copying machine of a first embodiment of the present invention; 
     FIG. 2 is a plan view of the operation panel of the digital copying machine shown in FIG. 1; 
     FIG. 3 is a first block diagram showing the construction of the controller  100  of the copying machine; 
     FIG. 4 is a second block diagram showing the construction of the controller  100  of the copying machine; 
     FIG. 5 is a block diagram of the image reader IR and the image signal processor  20 ; 
     FIG. 6 is a block diagram of the memory unit  30 ; 
     FIG. 7 is a first drawing showing the relationship between the management table MT 1  and the number memory unit  306 ; 
     FIG. 8 is a second drawing showing the relationship between the management table MT 1  and the number memory unit  306 ; 
     FIG. 9 is a drawing showing the sequence of the memory write operation in a simplified fashion; 
     FIG. 10 is a drawing showing the sequence of the memory read operation in a simplified fashion; 
     FIG. 11 is a main flow chart for the CPU  1  that controls the operation panel; 
     FIG. 12 is a main flow chart for the CPU  3  that controls the memory unit  30 ; 
     FIG. 13 is a main flow chart for the CPU  4  that controls the printer P; 
     FIG. 14 is a main flow chart for the CPU  5  that governs the control of the copying machine; 
     FIG. 15 is a flow chart showing the sequence of the processes of the key input subroutine in step # 13  of FIG. 11; 
     FIG. 16 is a flow chart showing the sequence of the processes of the serial number printing mode checking subroutine in step # 14  of FIG. 11; 
     FIGS.  17 ( a-c ) is a drawing to explain the display on the liquid crystal touch panel  201  when serial number printing is performed in the digital copying machine using memory recall; and 
     FIGS.  18 ( a-c ) is a drawing to explain the printing of images for which serial numbers are allocated by the digital copying machine using memory recall. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A digital copying machine, employing one embodiment of the present invention, is explained below with reference to the drawings. 
     FIG. 1 is a cross-sectional view showing the construction of the digital copying machine in which a first embodiment of the present invention is applied. With reference to FIG. 1, the digital copying machine comprises a scanning system  10  that reads the original document and converts it into image signals, an image signal processing unit  20  that processes the image signals sent from the scanning system  10 , a memory unit  30  that stores the image data input from the image signal processor  20  and outputs it to the printing processor, a printing processing unit  40  that drives the semiconductor laser  61  based on the image data output from the memory unit  30 , a laser optical system  60  that leads the laser beam from the semiconductor laser  61  to the exposure position on the photoreceptor drum  71 , an image forming system  70  that develops the latent image formed by the exposure, transfers it onto a sheet of recording paper and fuses it to the paper to form an image, an operation panel (not shown in FIG. 1) located on the top surface of the digital copying machine, and an original document feeding unit  500  that feeds the original document and flips it over where necessary. 
     The scanning system  10  and the image signal processing unit  20  comprise the image reading unit IR, and the print processing unit  40 , the laser optical system  60  and the image forming system  70  comprise the printing unit P. 
     The image reading unit IR reads the image of the original document placed on the platen glass  19  and generates image data that correspond to each pixel of the image of the original document. The first scanner  11  having an exposure lamp  12  and a first mirror  13   a  and the second scanner  14  having a second mirror  13   b  and a third mirror  13   c  move in the directions of the arrows b and b′ (the second scanning directions) by means of the driving by the scan motor M 2 . 
     The light from the exposure lamp  12  is reflected by the original document on the platen glass  19  and irradiates the line sensor (CCD)  17  via the mirrors  13   a ,  13   b  and  13   c  and the lens  15 . The line sensor  17  comprises a large number of photoelectric conversion elements aligned such that they are perpendicular to the sheet of paper on which FIG. 1 is printed (the main scanning directions). It reads the image at 400 dpi, for example, and outputs image data for each pixel. 
     When the first scanner  11  moves in the directions of the arrows b and b′, as described above, the line sensor  17  can perform secondary scanning of the original document image. The sensor SE 3  is a sensor to detect that the first scanner  11  is at the home position. 
     The image data output from the line sensor  17  is processed by the image signal processing unit  20  and is then sent to the memory unit  30 . The memory unit  30  compresses the image data received from the image signal processing unit  20  and saves it. It then expands the data and sends it to the printing unit P. When this is done, rotation editing, etc., are performed where necessary. 
     The memory unit  30  has an external device interface explained below, and is connected to an external device via an external device connector  90  and an external cable  91 . The image signal processing unit  20  and the memory unit  30  are explained in more detail below. 
     The printing unit P will now be explained. The print processing unit  40  controls the laser optical system  60  based on the image data received from the memory unit  30 . The laser optical system  60  has a semiconductor laser  61  that emits a laser beam that is modulated (ON/OFF control) by the print processing unit  40 , a polygon mirror  62  to cause the laser beam emitted from the semiconductor laser  61  to scan the photoreceptor drum  71 , an fθ lens  63 , and mirrors  64   a  and  64   b.    
     Around the photoreceptor drum  71  that is rotated are located, in the direction of the path of rotation, a charger  72 , a developing device  73 , a transfer charger  74 , a separation charger  75 , a cleaner  76  and an eraser lamp  77 . The photoreceptor drum  71  forms a toner image using the well-known electrophotographic process, and transfers it onto a sheet of paper. The paper is supplied from the paper supply cassette  81   a  or the paper supply cassette  81   b  by means of the paper supply rollers  82   a  or  82   b , and is sent to the position of the transfer charger  74  through the paper conveyance path  83  by means of the timing rollers  84 . The paper onto which the toner image has been transferred at the position of the transfer charger  74  is ejected toward the paper resupply unit  600  via the conveyance belt  85 , the fuser  86  and the paper eject rollers  87 . 
     The various rollers of the image forming system  70  and the photoreceptor drum  71  are driven by the main motor M 1 . Paper size detection sensors SE 1  and SE 2  are located in the vicinity of the paper supply cassettes  81   a  and  81   b , respectively, to detect the size of the paper housed in each cassette. 
     The original document feeding unit  500  automatically feeds the original document set on the original document feeding tray  510  and ejects the original document that was read by the scanning system  10  onto the original document ejection tray  511 . 
     In the normal mode, the user sets the original document, which comprises one or more sheets, on the original document feeding tray  510  such that the side to be read faces up, and adjusts the side regulator plate to the width of the original document. When the operation starts, the original document thus set is fed and conveyed sheet by sheet by means of the paper supply roller  501 , starting with the bottom sheet, after being flattened by the flattening roller  502  and the flattening pad  503 . The original document sheet being conveyed passes the intermediate rollers  504 , and its size is detected by the resist sensor SE 51  and the width sensor SE 53 . Any misalignment of the sheet is subsequently corrected by a resist roller  505 . Immediately after the trailing edge of the original document sheet has passed the left end of the original document scale  512 , the original document conveyance belt  506  travels backward slightly and then stops. As a result, the right end of the original document comes to contact with the edge of the original document scale  512 , such that the original document is set at the proper position on the platen glass  19 . When this is achieved, the leading edge of the next original document sheet is already located at the resist roller  505  so that the conveyance time for the next original document sheet may be reduced. 
     When the original document is set at the proper reading position on the platen glass  19 , reading of the original document by the scanning system  10  is performed. When the reading of the original document is completed, the original document sheet is conveyed to the left by means of the original document conveyance belt  506 , the direction of conveyance of the original document sheet is changed by the flipping roller  507 , and the original document sheet is ejected onto the original document ejection tray  511  after passing over the switching claw  508 . 
     Where the original document is two-sided, when the reading of the first side is completed, the original document is conveyed to the left by the original document conveyance belt  506 , and after the direction of conveyance is changed by means of the flipping roller  507 , it is sent onto the platen glass  19  again by means of the switching claw  508 , so that the second side of the original document is set at the reading position. 
     When the reading of the second side is completed, the original document sheet is conveyed to the left by the original document conveyance belt  506 , and ejected onto the original document ejection tray  511  via the flipping roller  507 , the switching claw  508  and the eject roller  509 . 
     The paper resupply unit  600  is mounted to one side of the printer as an additional device to automate two-sided copying. It has the function of housing the sheet of paper ejected from the main unit by means of the paper ejection rollers  87  and returning it to the printer main unit via switch-back conveyance. 
     In the single-sided copying mode, the sheet of paper passes through the paper resupply unit  600  and is ejected onto the paper ejection tray  621 . On the other hand, in the two-sided copying mode, the left end of the switching claw  601  moves upward by means of a solenoid not shown in the drawing, such that the sheet of paper ejected through the paper eject rollers  87  reaches the flipping rollers  603  via the conveyance rollers  602 . 
     When the trailing edge of the paper reaches the paper sensor SE 61 , the flipping rollers  603  rotate backward. This returns the paper to the printing unit P. The sheet of paper thus returned is sent to the timing rollers  84  via the horizontal conveyance rollers  88   a ,  88   b  and  88   c , whereupon it waits in standby status. 
     Where multiple sheets of paper are continuously supplied, the sheets are sequentially conveyed at certain intervals such that they do not overlap, and are then sent to the paper resupply unit  600 . Since the length of the paper conveyance path is unchanged, the number of sheets traveling in one cycle from the paper resupply unit  600  to the horizontal conveyance rollers  88   a  through  88   c  (the maximum number of cycling sheets) depends on the paper size. 
     FIG. 2 is a plan view of the operation panel of the digital copying machine shown in FIG.  1 . On the operation panel are located a liquid crystal touch panel  201  to display the status and to set various modes, a numeric keypad  202  to input the numerical copying conditions (the number of copies and the magnification), a clear key  203  to return the numerical settings to their default values, a panel reset key  204  to initialize the copy modes, a stop key  205  to instruct the apparatus to discontinue the copying operation, a start key  206  to instruct the apparatus to commence copying, an original document designation key  209  to designate whether the original document is one-sided or two-sided, a copy mode key  210  to alternate between two-sided copying and one-sided copying, and an interrupt key  208  to input interrupt activation and recovery. An ID card insertion slit  211  to insert an ID card  212  is also located on the operation panel. 
     This digital copying machine further has a memory recall function to save in the image memory the image data for the image for which printing has been completed and perform printing once again by reading this image data. It also has a serial number printing function to allocate a control number to each of multiple sets of printed images. The operator can select these functions by operating the prescribed touch keys displayed on the liquid crystal touch panel  201  (not shown in FIG.  2 ). 
     FIGS. 3 and 4 are block diagrams showing the construction of the controlling unit  100  of the copying machine. 
     With reference to FIGS. 3 and 4, the controlling unit  100  comprises mainly seven CPUs  1  through  7 . These CPUs  1  through  7  each have ROMs  111  through  117  in which programs are stored and RAMs  121  through  127  used as work areas for the execution of programs. The CPU  3  is located inside the memory unit  30 . 
     The CPU  1  performs control regarding the input of signals from the various operation keys on the operation panel as well as control regarding the display on the liquid crystal touch panel  201 . The CPU  2  performs control regarding the components of the image signal processing unit  20  and the driving of the scanning system  10 . The CPU  4  performs control regarding the print processing unit  40 , the laser optical system  60 , and the image forming system  70 . It also performs control regarding the main motor M 1 . The CPU  5  performs overall timing adjustment for the controlling unit  100  and processing for the setting of operation modes. 
     The CPU  3  controls the memory unit  30  and stores the image data read in the memory (the image memory unit  304  in FIG.  6 ). It then reads the data out and sends it to the print processing unit  40 . The memory unit  30  has a function to interface with an external device. The transfer of image data and control data is carried out via the memory unit  30 . 
     The signals from the paper size detection sensors SE 1  and SE 2  are input to the I/O unit controlled by the CPU  4 . The size of the copy paper is controlled by the CPU  4 . 
     The CPU  6  performs control regarding the conveyance of original documents by the original document feeding unit  500 . The CPU  7  performs control regarding the paper resupply unit  600 . 
     FIG. 5 is a block diagram of the image reading unit IR and the image signal processing unit  20 . In this drawing, the CPU  2 , the ROM  112 , the RAM  122  and the line sensor (CCD)  17  are those shown in FIG.  3 . With reference to FIG. 5, image read synchronization signals are supplied to each block by the timing controlling unit  21 . The CCD (line sensor)  17  performs photoelectric conversion of the original document information and generates electric signals. These signals are amplified by the amplifier (AMP)  23  and converted into 8-bit digital signals by the A/D converter  25 . These signals are processed by the shading correcting unit  26  such that distortion due to the optical system or the CCD is eliminated. Processing to convert the reflection data into density data, as well as gamma correction, are performed by the density converting unit  27 . 
     The signals output from the density converting unit  27  are input to the electric magnifying unit  28 , where electric magnification is carried out with regard to the main scanning directions based on the existing magnification information. Thereafter, the image data edited by the editing unit  29  is supplied to the printing unit P or the memory unit  30 . 
     The image monitor memory  24  saves image data for one line based on instructions from the CPU  2 . The CPU  2  performs overall control regarding the image reading unit IR, including the setting of parameters to the units  26  through  29 , scan control through the driving of the scanner motor M 2  and communication of the timing controller with the CPU  5  (the host CPU). 
     FIG. 6 is a block diagram of the memory unit  30 . With reference to FIG. 6, the memory unit  30  comprises a bus switching unit  301  that alternates the route for the image data among the image signal processing unit  20 , the print processing unit  40  and the interface unit  310 , an area determining unit  303  that determines binary areas from half-tone areas of the input image data, a binary processing unit  302  that generates binary image data based on the parameter settings from the CPU  3 , an image memory  304  having a capacity for two pages, a code processing unit  305  having a compressing unit  311  and an expanding unit  312  that can operate independently of each other, a multi-port code memory  306  having a capacity for large number of pages, an editing processing unit  307  that performs rotation, magnification and relocation, a multi-value processing unit  308  that generates multi-value image data from binary data stored in image memory  304  based on the parameter settings from the CPU  3 , a smoothing processing unit  309  that performs smoothing, and a CPU  3  that performs overall control regarding these components. 
     The bus switching unit  301  can transmit and receive image data to and from an external device via the interface unit  310 . Transmission of image data between the code memory  306  and the interface unit  310  can take place at the same time as the copying process taking place in the main unit. When that is done, the image data is compressed or expanded by the code processing unit  305  if necessary. 
     When copying is performed in the memory mode in which the image read via the scanning of the original document or the image input via the interface unit  310  from an external device is saved before it is used, 8-bit multi-value image data is input to the binary processing unit  302  of the memory unit  30  from the image signal processing unit  20  via the bus switching unit  301  and the area determining unit  303 . The binary processing unit  302  performs processing to convert the multi-value image data into binary image data to the recoverable extent possible using the error dispersion method or the dithering method. The binarized image data is written to the image memory  304 . 
     When the image data is written in the image memory  304 , the code processing unit  305  reads the data and compresses it to generate code data (compressed data). The code processing unit  305  then writes the code data in the code memory  306 . The code processing  305  also reads the code data, which is the object of printing, from the code memory  306  and expands it. It then writes the image data thus obtained in the image memory  304 . The compressing unit  311  and the expanding unit  312  can operate simultaneously and independently of each other in order to increase the copying speed. Data is transmitted between these devices and the code memory  306  using DMA transfer by means of a DMA controller not shown in the drawings. 
     When expanded image data is transmitted to the image memory  304 , editing of the expanded image data, such as rotation and/or magnification, is performed if necessary by the editing processing unit  307 . Where the serial number printing mode is selected, the editing processing unit  307  synthesizes image data that corresponds to the serial number to be allocated to the expanded image data. 
     When image data for one page is reproduced through expansion and editing, the data is read from the image memory  304 . The data thus read is recovered as multi-value data by the multi-value processing unit  308  and the smoothing processing unit  309 , depending on the mode present, and undergoes smoothing if necessary. This multi-value image data is transmitted to the print processing unit  40  or to an external device via the interface unit  310 . 
     When the original document image is temporarily saved in this way, the code memory  306  is managed using the management table MT 1  stored in the RAM  123 . 
     FIGS. 7 and 8 show the relationship between the management table MT 1  and the code memory  306 . The code memory  306  is divided into 32K memory areas. In order to make simultaneous writing (when an image is read) and reading (when printing is performed) possible, each area houses code data for each page. 
     Stored in the management table MT 1  are the number that indicates the area in the code memory  306 , the page number PN for the image data, which is provided in the order of writing (the order of the scanning of the sheets of the original document), the number of the associated area, and various additional information necessary for the compression and expansion processes, such as the method of compression and the data size. The code memory  306  is actively managed based on this information. 
     The ‘front connection’ in FIG. 7 indicates the relationship to the previous 32K area for page data. Where it is ‘00’, it means that the area is the first storage area for one-page data. The ‘rear connection’ similarly indicates the relationship to the next 32K area for page data. Where it is ‘FF’, it indicates that the area is the last area and where it is something other than ‘FF’, it indicates the number of the subsequent area. 
     When the compressing unit  311  reads image data from the image memory  304  and compresses it, the CPU  3  controls the compressing unit  311  with reference to the information in the management table MT 1  and stores the image data in the code memory  306 . When the image data is output, the code data is read from the code memory  306  via a reverse operation. 
     The operation sequence of this digital copying machine will now be explained with a focus on the request commands (Q) and the reports (A) that are sent and received between the CPUs, or the data flow. FIG. 9 shows the sequence of the memory write operation in a simplified fashion. In the write operation, image data is transmitted from the image signal processing unit  20  to the image memory  304 . 
     With reference to FIG. 9, the CPU  5 , which controls the overall sequence, first sends a memory preparation request to the CPU  3 . Upon receiving the request, the CPU  3  sets in the internal hardware components the bus connection to transmit the image data from the image signal processing unit  20  to the image memory  304 , the mode for binarization, and the first write area address in the image memory  304  and XY length information. 
     When these settings are made and preparation is completed, the CPU  3  notifies the CPU  5  of the completion of the memory preparation. 
     When the CPU  5  sends a read request to the CPU  3  and the CPU  2 , the CPU  2  sends a scan request to the internal original document scanning unit. 
     When the original document scanning unit begins scanning and the first scanner  11  reaches the image area, the read data (the image data) is transmitted from the image signal processing unit  20  to the memory unit  30  depending on the image processing mode set by the CPU  2 . 
     When the scanning is completed and the CPU  2  and the CPU  3  notify the CPU  5  of the completion of reading, the CPU  5  sends a data compression request to the CPU  3 . Upon receiving this request, the CPU  3  sets the read address from the image memory  304 , the XY length information, the write address in the code memory  306 , and the compressing unit  311  mode (such as arithmetic encoding method or MH method, for example), and activates various components. In this way, compression takes place and code data is saved in the code memory  306 . 
     When the compression process is completed, the CPU  3  notifies the CPU  5  of the completion of compression. If the code memory  306  is full when the notification is made, a compression completed report including a parameter indicating compression disabled is sent to the CPU  5 . As a result, the CPU  5  learns that the code memory  306  is full. 
     FIG. 10 shows the sequence of the memory read operation in a simplified fashion. In the memory read operation, image data is read from the image memory  304  and a copy image is printed on the sheet of paper based on the image data. To describe it in more detail, with reference to FIG. 10, the CPU  5  sends a data expansion request to the CPU  3 . The CPU  3  sets the read address from the code memory  306 , the data size, the write address in the image memory  304 , the XY length information, the expanding unit  312  mode (such as arithmetic encoding method or MH method, for example), and the editing mode such as rotation, and activates various components. In this way, expansion takes place and the image data is saved in the image memory  304 . 
     When the expansion process is completed, a completion report is sent from the CPU  3  to the CPU  5 . The CPU  5  then outputs to the CPU  3  a memory preparation request to read the image data from the image memory  304 . Upon receiving this request, the CPU  3  sets in the internal hardware components the bus connection to transmit the image data from the image memory  304  to the print processing unit  40 , the first read area address in the image memory  304  and the XY length information. 
     When setting of these parameters is completed and the CPU  5  is notified of the completion, the CPU  5  sends a print request to the CPU  3  and the print processing unit  40 . 
     A paper supply report regarding the paper conveyance is sent from the print processing unit  40  to the CPU  5 , and then the image data read from the image memory  304  is output to the print processing unit  40 , whereupon printing is carried out. 
     When printing is completed, the CPU  3  and the print processing unit  40  send a print completed report and an eject completed report to the CPU  5 . Upon receiving these reports, the CPU  5  sends a memory clear request to the CPU  3  if necessary. 
     The control by the CPU  1  and the CPUs  3  through  5  pertaining to the present invention will now be explained with reference to FIGS. 11 through 16. FIG. 11 is a main flow chart for the CPU  1  that performs control regarding the operation panel. 
     When power is turned ON, the CPU  1  first performs initialization to initialize the RAM, registers, etc. (step # 11 ). It then sets the internal timer that regulates the length of one routine (step # 12 ) and repeats the key input routine in which key operations are accepted (step # 13 ), the serial number printing mode checking routine in which it is determined whether the serial number printing mode is selected (step # 14 ), the panel display routine in which display in response to the operation is performed (step # 15 ), other routines (# 16 ), and the waiting for the internal timer to come to an end (step # 17 ). It also communicates with other CPUs in the form of an interrupt routine where necessary. 
     The key input routine (step # 13 ) and the serial number printing mode checking routine (step # 14 ) will be explained in detail below. 
     FIG. 12 is a main flow chart for the CPU  3  that performs control regarding the memory unit  30 . After performing initialization (step # 31 ), the CPU  3  determines whether or not the memory recall key flag F is ‘1’. The memory recall key flag F is set to ‘1’ when the memory recall mode is selected in the key input routine shown in FIG. 15, and is set to ‘0’ when the memory recall mode is not selected. 
     Where the memory recall key flag F is 0, (NO in step # 32 ), the command receive routine (step # 33 ), the status report transmission routine (step # 34 ), the image memory write routine (step # 35 ), and the compression control routine (step # 36 ) are performed, followed by the expansion control routine (step # 37 ), the image memory read routine (step # 38 ) and other routines (step # 39 ). 
     On the other hand, where the memory recall key flag F is ‘1’ (YES in step # 32 ), the command acceptance routine (step # 33 A) and the status report transmission routine (step # 34 A) are performed, followed by the expansion control routine (step # 37 ), the image memory read routine (step # 38 ) and the other routines (step # 39 ). 
     The difference in processing regarding the memory unit  30  between when the memory recall mode is selected and when it is not selected is that, in the memory recall mode, the image data is stored in the memory and the image is formed directly using this image data, and the routine to write the image in the memory (step # 35 ) and the routine to compress the image (step # 36 ) are not necessary. 
     FIG. 13 is a main flow chart for the CPU  4  that performs control regarding the printing unit P. After performing initialization (step # 41 ), the CPU  4  repeats the setting of the internal timer (step # 42 ), the control regarding the developing and transfer systems (step # 43 ), the control regarding the conveyance system (step # 44 ), the control regarding the fusing system (step # 45 ), the control regarding the print processing unit (step # 46 ), other routines (step # 47 ) and the waiting for the internal timer to come to an end (step # 48 ). 
     FIG. 14 is a main flow chart for the CPU  5  that oversees the control regarding the copying machine. After performing initialization (step # 51 ), the CPU  5  repeats the setting of the internal timer (step # 52 ), the input data analysis routine in which the data input from other CPUs is checked (step # 53 ), the mode setting routine in which the operation mode is determined depending on the parameters set (step # 54 ), the interrupt switching routine (step # 55 ), the command setting routine in accordance with the mode (step # 56 ), the output data setting in which a command is placed standing-by in the communication port (step # 57 ), the other routines (step # 58 ) and the waiting for the internal timer to come to an end (step # 59 ). 
     The key input subroutine in step # 13  and the serial number printing mode checking subroutine in step # 14  of FIG. 11 will now be explained. 
     FIG. 15 is a flow chart showing the sequence of the processes of the key input subroutine in step # 13  of FIG.  11 . When the display shown in FIG. 17 ( c ) is shown on the liquid crystal touch panel  201 , it is determined in the key input routine whether or not the ‘memory recall’ key  2011 , which is a touch key, has been pressed in step # 61 . Where the ‘memory recall’ key  2011  has been pressed (YES in step # 61 ), the memory recall key flag F is set to ‘1’ in step # 62 . Where the ‘memory recall’ key  2011  has not been pressed (NO in step # 61 ), the memory recall key flag F is set to ‘0’ in step # 63 . The other routines are performed in step # 64 . When these processes are performed, this key input routine comes to an end. The status of the memory recall key flag F is communicated to the CPU  3  via the CPU  5  in the transmission process included in the other routines of step # 64 . 
     FIG. 16 is a flow chart showing the sequence of processes of the serial number printing mode checking subroutine in step # 14  of FIG.  11 . In the serial number printing mode checking routine, it is first determined in step # 71  whether or not the memory recall key flag F is ‘1’. Where the memory recall key flag F is ‘1’ (YES in step # 71 ), it is determined in step # 72  whether or not the serial number printing mode is selected. The selection of the serial number printing mode is carried out by pressing the ‘serial number print’ key  2012 , which is a touch key, when the display shown in FIG. 17 ( d ) is shown on the liquid crystal touch panel  201 . If the memory recall key flag F is ‘1’ (i.e., the memory recall mode is selected) and the serial number printing mode is selected (YES in step # 72 ), a number comprising the last management number allocated to the immediately prior print job plus one is set as the starting serial number (the first serial number that starts the set of serial numbers allocated to the print job to manage the number of sets of printed images) in step # 73 , and this number is communicated to the CPU  3  via the CPU  5 . 
     On the other hand, where the memory recall flag F is ‘0’ (NO in step # 71 ), it is determined in step # 74  whether the serial number printing mode is selected. If the memory recall key flag F is ‘0’ (i.e., if the memory recall mode is not selected) and the serial number printing mode is selected (YES in step # 74 ),  1  is set as the starting serial number in step # 75  and this number is communicated to the CPU  3  via the CPU  5 . 
     After these processes, the memory recall key flag F is set to ‘0’ in step # 76 , whereupon this serial number printing mode checking routine comes to an end. 
     In this digital copying machine, the control described above entails displays on the liquid crystal touch panel  201  that are shown in FIGS.  17 ( a )- 17 ( d ), and printing of images that is explained with reference to FIGS.  18 ( a )- 18 ( c ) is performed through this control. 
     FIGS.  17 ( a )- 17 ( d ) are drawings to explain the display on the liquid crystal touch panel  201  when serial number printing is performed using the memory recall function in this digital copying machine. It is displayed on the liquid crystal touch panel  201  of this digital copying machine that the user has input ‘ 4 ’ as the number of copies to make, as shown in FIG.  17 ( a ), and when copying is started by the pressing of the start key  206 , it is displayed that copying is underway, as shown in FIG.  17 ( b ). 
     When the copying is completed, ‘The previous images may be printed again. Please press the memory recall key’ is displayed on the liquid crystal touch panel  201 , as shown in FIG.  17 ( c ), indicating that the memory recall mode is available. If the user presses the ‘memory recall’ key  2011  at this point, the memory recall mode is selected and the display of FIG.  17 ( d ) appears. 
     In the display shown in FIG.  17 ( d ), the number of copies that the user is to make is input as ‘3’. The ‘serial number printing’ key  2012  is also displayed, indicating that the serial number printing mode is available. When the user presses the ‘serial number printing’ key  2012 , and then the start key  206  in response to the display ‘Starting printing. Please press the start key’, serial number printing as shown in FIGS.  18 ( a )- 18 ( c ) is performed. 
     FIGS.  18 ( a )- 18 ( c ) are drawings to explain the printing of images with serial numbers when the memory recall function is used in this digital copying machine. In this digital copying machine, when four copies of an image are printed using the procedure explained with reference to FIGS.  17 ( a ) and  17 ( b ), and three more copies of the same image are printed using the memory recall function and the serial number printing function via the procedure explained with reference to FIGS.  17 ( c ) and  17 ( d ), management numbers  5 ,  6  and  7  are allocated to each of the printed images as shown in FIG.  18 ( a ). 
     It is possible to allocate the same number to multiple different printed images that comprise one set of printed images, as shown in FIG.  18 ( b ), or to allocate the number to a specific image among multiple different printed images comprising a set of printed images, i.e., the printed image that is ejected as the first page of the set of printed images, for example, as shown in FIG.  18 ( c ). 
     In the digital copying machine of this embodiment, the starting serial number is automatically determined based on the numbers (serial numbers) used in the previous print job, but it is also acceptable if the construction is such that the user can set any number. 
     Using the digital copying machine of this embodiment explained above, when using stored image data and allocating a number to each set of printed images, the operation by the user is simpler and an operation inconvenient for the user is not necessary, while the number of sets of formed images is accurately managed. 
     Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.