Abstract:
This invention is directed to an image printing apparatus including an image printing unit which prints an image on the basis of image data, a storage unit which stores information concerning details of a message for operating the image printing apparatus, and a display unit which displays the message and, when a message for which the information concerning the details of the message is stored in the storage unit is displayed, also displays identification information which indicates that the details of the message can be displayed. The image printing apparatus further includes a control unit which causes the display unit to display a message, and an operating unit which allows the user to perform input operation through a help key for selecting a help function. When causing the display unit to display a message, the control unit recognizes whether or not information concerning the details of the message is stored in the storage unit. Upon recognizing that the information is stored, the control unit causes the display unit to display identification information together with the message.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an image printing apparatus which prints an image on a sheet by, for example, electrophotography and a display control method for the apparatus. 
   2. Description of the Prior Art 
   An electrophotographic image printing apparatus such as a digital copying machine is known well, which forms a latent image by exposing the uniformly charged photosensitive layer of a photosensitive body to light, develops the latent image by making toner adhere to the photosensitive layer, and transfers the image onto a sheet, thus performing image printing. 
   Such an image printing apparatus has recently become increasingly multifunctional. Accordingly, the operation method and the like have become complicated, and so the user cannot memorize all the functions and sometimes needs to check an operation method or the like. 
   As an image printing apparatus becomes multifunctional, a so-called instruction manual, manual, or the like becomes large in volume. As a consequence, the user cannot easily consult the instruction manual. It is also very difficult for the user to find out necessary information. 
   In addition, when the user operates the image printing apparatus while looking at such a manual, the possibility of making an error in the operation of the apparatus increases because of, for example, difficulty in consulting the manual. 
   The invention disclosed in Japanese Unexamined Patent Publication No. 62-3260 has been made under such circumstances, and is designed to display an operation method in text form on the operation panel of an image printing apparatus, thereby allowing the user to reliably perform his/her desired operation without any confusion. 
   It is known that in a conventional image printing apparatus, a help function of explaining operation in the apparatus when a help key is pressed is provided for an operating unit having both the function of a display unit which displays information to a user and the function of an input unit which receives an input from the user. The help function of the conventional image printing apparatus will be described below with reference to  FIGS. 1A and 1B  and  FIGS. 2A and 2B . 
     FIGS. 1A and 1B  are views showing display examples on the operation panel of the conventional image printing apparatus.  FIG. 1A  is a view showing a display window before pressing of the help key.  FIG. 1B  is a view showing a display window after pressing of the help key. 
     FIGS. 2A and 2B  are views showing display examples on the operation panel of the conventional image printing apparatus.  FIG. 2A  is a view showing another example of the display window after pressing of the help key.  FIG. 2B  is a view showing an example of the display window displayed when a hard key is selected in the display window shown in  FIG. 2A . 
   Referring to  FIGS. 1A and 1B  and  FIGS. 2A and 2B , reference numeral  200  denotes a display window. Referring to  FIGS. 2A and 2B , reference numeral  201  denotes a button for selecting display of an explanation of the hard key provided in the image printing apparatus. 
     FIG. 1A  shows a window for setting reading conditions for the operation of making the image printing apparatus read an original image. If the items displayed in the window  200  include any unclear item which demands an explanation, the user presses a help key (not shown). 
   When the help key is pressed while the window  200  in  FIG. 1A  is displayed, the window  200  switches to the window  200  which displays explanations of the respective items displayed in the window  200  in  FIG. 1A . 
   Alternatively, when the user presses the help key, a help menu like the one shown in  FIG. 2A  can be displayed. 
   When the user presses a button assigned to one of the items in the window  200  of the help menu in  FIG. 2A  which corresponds contents which the user wants to know, the window  200  switches to the window  200  which displays an explanation of the item, as shown in  FIG. 2B .  FIG. 2B  shows the display window  200  displayed when the user presses the button  201 . 
   The following problems arise in the conventional image printing apparatus described above. 
   In the conventional image printing apparatus, when the user presses the help key, an explanation can be displayed to the user. However, since it is difficult for the user to specify information which he/she wants to know, information including explanations of various items like those shown in.  FIG. 1B  is displayed. That is, information which the user wants to know is not timely displayed. In addition, since explanations of various items are displayed in this manner, when such information is displayed within a limited display area, a sufficient explanation cannot be displayed. 
   Furthermore, in the prior art, as shown in  FIGS. 2A and 2B , although explanations of buttons, functions, and the like which are provided in advance are displayed, no explanation is given to the user concerning the state of the image printing apparatus which changes with the progress of operation, i.e., the state in which no copying operation can be done even when the copy start button is pressed to copy an original. This leads to poor operability. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in consideration of the above problems in the prior art, and has as its first object to provide an image printing apparatus which achieves an improvement in usability for a user. It is the second object of the present invention to provide an image printing apparatus which achieves an improvement in usability by providing a help for the user in accordance with the operation state of the apparatus. It is the third object of the present invention to provide an image printing apparatus which can shorten the time required to reach information which the user wants to know. 
   In order to achieve the above objects, according to the first aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on the basis of image data, a storage unit which stores information concerning details of a message for operating the image printing apparatus, and a display unit which displays the message and, when a message for which the information concerning the details of the message is stored in the storage unit is displayed, displays identification information which indicates that the details of the message can be displayed. 
   According to the second aspect of the present invention, the image printing apparatus of the first aspect further comprises a control unit which causes the display unit to display the message, the storage unit stores the information concerning the details of the message in correspondence with information concerning the message, and the control unit recognizes whether or not information concerning the details of the message is stored in the storage unit, when causing the display unit to display the message, and causes the display unit to display identification information together with the message, when recognizing that the information is stored. 
   According to the third aspect of the present invention, in the image printing apparatus of the second aspect, the storage unit stores corresponding information which indicates that the information concerning the details of the message is stored in correspondence with the information concerning the message, and the control unit recognizes on the basis of the corresponding information whether or not the information concerning the details of the message is stored in the storage unit. 
   According to the fourth aspect of the present invention, the image printing apparatus of the second aspect further comprises an operating unit having a help key which is operated by a user to instruct the display unit to display a help message, the control unit changes display contents on the display unit when the operating unit is operated, and the identification information is information for identifying each of a plurality of messages displayed by the designating unit as a message for which whether or not the information concerning the details of the message can be displayed on the display unit. 
   According to the fifth aspect of the present invention, in the image printing apparatus of the fourth aspect, the control unit causes the display unit to display the details of the message on the basis of the information concerning the details of the message when the help key is operated while the identification information is displayed on the display unit together with the message. 
   According to the sixth aspect of the present invention, in the image printing apparatus of the fourth aspects the message is displayed on the display unit together with a setting window for setting a condition for formation of the image, and the control unit causes the display unit to display details of the message on the basis of information concerning the details of the message when the help key is operated while the identification information is displayed, and causes the display unit to display the details of the setting window when the help key is operated while the identification information is not displayed on the display unit together with the message. 
   According to the seventh aspect of the present invention, in the image printing apparatus of the fourth aspect, the message is displayed on the display unit together with a setting window for setting a condition for formation of the image, and the control unit causes the display unit to display information concerning details of the message when the help key is operated while the identification information is displayed, and causes the display unit to display detailed information concerning the setting window when the help key is operated while the identification information is not displayed on the display unit, and the detailed information concerning the setting window is stored in the storage unit. 
   According to the eighth aspect of the present invention, in the image printing apparatus of the seventh aspect, the storage unit stores the detailed information concerning the setting window in correspondence with the information concerning the setting window, and the control unit determines whether or not the detailed information concerning the setting window is stored in the storage unit, when the help key is operated while the identification information is not displayed on the display unit, and causes the display unit to display the setting window, when determining that the detailed information is stored in the storage unit. 
   According to the ninth aspect of the present invention, in the image printing apparatus of the fifth aspect, the message and the details of the message are an operation instruction for the user and details of the operation instruction, respectively, and the control unit causes the display unit to display the details of the operation instruction when the help key is operated while the identification information is displayed on the display unit together with the operation instruction for the user. 
   According to the 10th aspect of the present invention, in the image printing apparatus of the fifth aspect, the message and the details of the message are a message stating that image printing cannot be started and details indicating that image printing cannot be started, respectively, and the control unit causes the display unit to display details indicating that the image printing cannot be started, when the help key is operated while the identification information is displayed on the display unit together with the message stating that the image printing cannot be started. 
   According to the 11th aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on the basis of image data, an operating unit operated by a user, a display unit which changes display contents when the operating unit is operated, and a control unit which controls the display unit, wherein the operating unit includes a help key for selecting a help function, and the control unit causes the display unit to display details indicating that image printing cannot be started, when the help key is operated while a message stating that image printing cannot be started is displayed on the display unit. 
   According to the 12th aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on the basis of image data, an operating unit operated by a user, a display unit which changes display contents when the operating unit is operated, and a control unit which controls the display unit, wherein the operating unit includes a help key for selecting a help function, and the control unit causes the display unit to display details of an instruction operation for the user, when the help key is operated while message indicating the operation instruction for the user is displayed on the display unit. 
   According to the 13th aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on the basis of image data, an operating unit operated by a user, a display unit which displays a setting window for setting a condition for formation of the image together with a message, a storage unit which stores information concerning details of the message, and a control unit which controls the display unit, wherein the operating unit includes a help key for selecting a help function, and the control unit causes the display unit to display the details of the message, if information concerning the details of the message corresponding to the message displayed on the display unit is stored in the storage unit when the help key is operated, and causes the display unit to display details of the setting window if information concerning the details of the message corresponding to the message displayed on the display unit is not stored in the storage unit. 
   According to the 14th aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on a sheet on the basis of image data, a control unit which controls operation of the image printing apparatus, an operating unit which allows the user to perform input operation, and an display unit which changes a display window in accordance with a key input, wherein the operating unit includes a help key for allowing the user to select a help function, and the control unit controls the display unit to display details indicating that image printing cannot be started, when the help function is selected by the help key while the display unit is displaying information indicating that the image printing cannot be started. 
   According to the 15th aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on a sheet on the basis of image data, a control unit which controls operation of the image printing apparatus, an operating unit which allows the user to perform input operation, and a display unit which changes a display window in accordance with a key input, wherein the operating unit includes a help key for allowing the user to select a help function, and the control unit controls the display unit to display details of an operation instruction for the user, when the help function is selected by the help key while the display unit is displaying information for the operation instruction for the user. 
   According to the 16th aspect of the present invention, there is provided an image printing apparatus comprising an image printing unit which prints an image on a sheet on the basis of image data, a control unit which controls operation of the image printing apparatus, an operating unit which allows the user to perform input operation, and a display unit which changes a display window in accordance with a key input, wherein the operating unit includes a help key for allowing the user to select a help function, and the control unit controls the display unit to display identification information for allowing the user to identify each of a plurality of messages displayed on the display unit as a message for which whether or not details of the message can be displayed through the help function. 
   According to the 17th aspect of the present invention, there is provided a display control method for an image printing apparatus including an image printing unit which prints an image on a sheet on the basis of image data, a control unit which controls operation of the image printing apparatus, an operating unit which allows the user to perform input operation, and a display unit which changes a display window in accordance with a key input, the operating unit including a help key for allowing the user to select a help function, comprising, when the help function is selected by the help key while the display unit is displaying information indicating that image printing cannot be started is displayed, controlling the display unit to display details indicating that the image printing cannot be started. 
   According to the 18th aspect of the present invention, there is provided a display control method for an image printing apparatus including an image printing unit which prints an image on a sheet on the basis of image data, a control unit which controls operation of the image printing apparatus, an operating unit which allows the user to perform input operation, and a display unit which changes a display window in accordance with a key input, the operating unit including a help key for allowing the user to select a help function, comprising, when the help function is selected by the help key while the display unit is displaying an operation instruction for the user, controlling the display unit to display details of an operation instruction for the user. 
   According to the 19th aspect of the present invention, there is provided a display control method for an image printing apparatus including an image printing unit which prints an image on a sheet on the basis of image data, a control unit which controls operation of the image printing apparatus, an operating unit which allows the user to perform input operation, and a display unit which changes a display window in accordance with a key input, the operating unit including a help key for allowing the user to select a help function, comprising controlling the display unit to display identification information for allowing the user to identify each of a plurality of messages displayed by the display unit as a message for which whether or not details of the message can be displayed through the help function. 
   As is obvious from the respective aspects described above, according to the present invention, when a message for which information concerning the details of the message is stored in the storage unit is to be displayed, identification information indicating that the details of the message can be displayed is displayed. This makes it possible to provide an image printing apparatus which has achieved an improvement in usability for the user. 
   When the help key is operated while a message stating that image printing cannot be started is displayed, the details of the message are displayed. This makes it possible to provide an image printing apparatus which has achieved an improvement in usability by providing the user with a help corresponding to the operation state of the image printing apparatus. 
   When the help key is operated while a message indicating an operation instruction is displayed to the user, the details of the operation instruction are displayed to the user. This makes it possible to provide an image printing apparatus which can shorten the time required to reach information which the user wants to know. 
   The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which a preferred embodiment incorporating the principle of the present invention is shown by way of illustrative examples. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  show display examples on the operation panel of a conventional image printing apparatus, in which  FIG. 1A  is a view showing an example of the display window displayed before the help key is pressed, and  FIG. 1B  is a view showing an example of the display window displayed after the help key is pressed; 
       FIGS. 2A and 2B  show display examples on the operation panel of the conventional image printing apparatus, in which  FIG. 2A  is a view showing another example of the display window displayed after the help key is pressed, and  FIG. 2B  is an example of the display window displayed when a hard key is selected in the display window shown in  FIG. 2A ; 
       FIG. 3  is a schematic sectional view showing the arrangement of an electrophotographic copying machine as an embodiment of an embodiment of the present invention; 
       FIG. 4  is a block diagram showing constituent elements which controls the image printing apparatus shown in  FIG. 3 ; 
       FIG. 5  is a flow chart showing an example of an operation sequence for help function processing in the image printing apparatus shown in  FIG. 3 ; 
       FIG. 6  is a flow chart showing another example of the operation sequence for the help function processing in the image printing apparatus shown in  FIG. 3 ; 
       FIG. 7  is a flow chart showing still another example of the operation sequence for the help function processing in the image printing apparatus shown in  FIG. 3 ; 
       FIG. 8  is a view showing a display window for designating a stapling position as an example of display contents on an operation panel included in the operating unit of the image printing apparatus shown in  FIG. 3 ; 
       FIG. 9  is a view showing a display window for designating a binding direction in double-sided printing as an example of display contents on the operation panel included in the operating unit of the image printing apparatus shown in  FIG. 3 ; 
       FIG. 10  is a view showing a display window to be displayed when the operation shown in  FIGS. 8  or  9  is performed as an example of display contents on an operation panel included in the operating unit of the image printing apparatus shown in  FIG. 3 ; 
       FIG. 11  is a view showing a display window to be displayed when the help key is pressed in the state in  FIG. 10  as an example of display contents on an operation panel included in the operating unit of the image printing apparatus shown in  FIG. 3 ; 
       FIG. 12  is a view showing a display window to be displayed when the help key is pressed in the state in  FIG. 10  as an example of display contents on an operation panel included in the operating unit of the image printing apparatus shown in  FIG. 3 ; and 
       FIG. 13  is a view showing a display window concerning the detailed information of a currently displayed setting window when a message for which no help window is prepared is displayed. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. 
     FIG. 3  is a schematic sectional view showing the arrangement of an image printing apparatus according to an embodiment of the present invention. An electrophotographic copying machine will be described as the image printing apparatus according to the embodiment of the present invention. 
   The arrangement and basic operation of an image printing apparatus  100  according to this embodiment will be described with reference to  FIG. 3 . 
   Although an image printing apparatus capable of printing color images will be described in this embodiment, it is obvious that the present invention is not limited to this, and can be applied to an image printing apparatus capable of printing only monochrome images. 
   The image printing apparatus  100  includes a plurality of document writing units  153 Y,  153 M, and  153 C for a color image printing unit, and a document writing unit  154 K for a monochrome image printing unit. The document writing unit  153 Y can form yellow images; the document writing unit  153 M, magenta images; the document writing unit  153 C, cyan images, and the document writing unit  154 K, black images. 
   This apparatus includes photosensitive bodies  6 Y,  6 M,  6 C, and  6 K, charging units  7 Y,  7 M,  7 C, and  7 K, and developing units  8 Y,  8 M,  8 C, and  8 K in correspondence with the document writing units  153 Y,  153 M,  153 C, and  154 K. The apparatus also includes an intermediate transfer unit  9  common to the above color image printing unit and monochrome image printing unit. The intermediate transfer unit  9  includes an intermediate transfer body  9   a  in the form of an endless belt which is wound around a plurality of rollers and is so placed as to be able to come into contact with the photosensitive bodies  6 Y,  6 M,  6 C, and  6 K, and primary transfer units  9 Y,  9 M,  9 C, and  9 K which make the intermediate transfer body  9   a  come into contact with the photosensitive bodies  6 Y,  6 M,  6 C, and  6 K to transfer images. 
   Other components will be described next. An original reading unit  1  functioning as a scanner unit is mounted on the upper portion side of the image printing apparatus  100 . An original is set on a glass surface as a platen. The original reading unit  1  then reads the original. The original reading unit  1  incorporates a CCD  131  to which reflected light obtained by the above scanning operation is input. Although not shown in  FIG. 3 , the original reading unit may include an ADF (Automatic Document Feeder). 
   Paper trays  2 ,  3 , and  4  are arranged in the lower portion of the image printing apparatus  100 , and paper feed units  2   a,    3   a,  and  4   a  are respectively provided for the paper trays. A manual paper tray  5  is provided in an outer side wall portion of the image printing apparatus  100 . A paper feed unit  5   a  is provided for the manual paper tray  5 . Since a plurality of types of paper trays and manual paper tray are provided in this manner, a plurality of types of sheets having different sizes can be used. 
   Registration rollers  15  are arranged ahead of the paper feed side of the paper feed units  2   a  to  5   a . A secondary transfer roller  16  which can press a sheet against the intermediate transfer body  9   a  is placed ahead of the registration rollers  15 . A fixing unit  17  is placed ahead of the secondary transfer roller  16 . Delivery rollers  18  are provided ahead of the fixing unit  17 . 
   In the image printing apparatus  100 , in accordance with an image printing command, when color printing is performed, the images formed as needed by the document writing units  153 Y,  153 M,  153 C, and  154 K are transferred onto the intermediate transfer body  9   a  by the photosensitive bodies  6 Y,  6 M,  6 C, and  6 K, charging units  7 Y,  7 M,  7 C, and  7 K, developing units  8 Y,  8 M,  8 C, and  8 K, and primary transfer units  9 Y,  9 M,  9 C, and  9 K. When monochrome printing is performed, the image formed by the document writing unit  154 K is transferred onto the intermediate transfer body  9   a  by the photosensitive body  6 K, charging unit  7 K, developing unit  8 K, and primary transfer unit  9 K. 
   A sheet necessary for image printing is fed from one of the paper trays  2 ,  3 , and  4  or the manual paper tray  5  in accordance with the paper size or the like by a corresponding one of the paper feed units  2   a ,  3   a ,  4   a , and  5   a . The sheet then reaches the secondary transfer roller  16  through the registration rollers  15 . The sheet is pressed against the intermediate transfer body  9   a  by the secondary transfer roller  16 , and the image on the intermediate transfer body  9   a  is transferred onto the sheet. The fixing unit  17  fixes the transferred image on the sheet. The sheet is then delivered out of the image printing apparatus  100  through the delivery rollers  18 . 
     FIG. 4  is a block diagram showing an arrangement for control on the image printing apparatus  100  in  FIG. 3 . 
   As shown in  FIG. 4 , the image printing apparatus  100  is comprised of a control unit  101  which performs overall control on the image printing apparatus  100 , an image reading unit  105  which has the original reading unit  1  and reads an image from an original, an image printing unit  106  which has the document writing units  153 Y,  153 M,  153 C, and  154 K and prints images on image printing sheets like a paper sheet, a storage unit  102  which stores the image data and the like read by the image reading unit  105 , the programs to be executed by the control unit  101 , parameters necessary for the operation of the image printing apparatus  100 , and the like, an operating unit  103  which displays information from the image printing apparatus  100  to the user and allows the user to input operations, instructions, and the like to the image printing apparatus  100 , and a postprocessing device  110  which, for examples, staples sheets on which images are printed and forms holes for filing. 
   The operating unit  103  is comprised of, for example, a touch panel type operation panel  115  (to be described later) and a fixed button type operating unit (not shown). In this embodiment, a help key (not shown) which is used by the user to select a help function is provided on the fixed button type operating unit. However, a help key may be provided on the operation panel  115 . 
   The operating unit  103  may include a display panel unit such as a CRT, liquid crystal display, or EL display and an input device unit such as a touch panel or mouse which detects a coordinate position corresponding to a button position on the display panel. 
   The operation of this embodiment will be described in detail next with reference to the accompanying drawings. 
     FIG. 5  is a flow chart showing an example of the processing operation of the help function in the image printing apparatus  100  shown in  FIG. 3 . 
   The control unit  101  of the image printing apparatus  100  detects that the help key is pressed by the user on the operating unit  103  (A- 1 ). 
   Upon detecting that the help key is pressed by the user, the control unit  101  checks the message currently displayed on the operation panel  115  of the operating unit  103  (A- 2 ). 
   The control unit  101  then checks whether or not the currently displayed message is a “start disable message”, e.g., a message stating that copying operation cannot be started is displayed even when the user has issued an instruction to start copying operation by using the operating unit  103 , or a message stating that image printing cannot be started is displayed (A- 3 ). 
   If the “start disable message” is currently displayed, a help window as an explanation of the currently displayed “start disable message” is displayed on the operating unit  103  (A- 4 ). The contents to be displayed may be stored in the storage unit  102  in advance to be read out as needed. 
   If it is determined in step (A- 3 ) that the “start disable message” is not currently displayed, a help window as an explanation of the currently displayed window is displayed on the operating unit  103  (A- 5 ). The contents to be displayed in this step may also be stored in the storage unit  102  in advance to be read out as needed. 
   The operation processing in this embodiment in a situation different from that shown in  FIG. 5  will be described next. 
     FIG. 6  is a flow chart showing an example of the processing sequence of the help function in the image printing apparatus  100  in this embodiment shown in  FIG. 3 , which is different from the example shown in  FIG. 5 . 
   The control unit  101  of the image printing apparatus  100  detects that the help key is pressed by the user on the operating unit  103  (B- 1 ). 
   Upon detecting that the help key is pressed by the user, the control unit  101  checks the message currently displayed on the operation panel  115  of the operating unit  103  (B- 2 ) 
   The control unit  101  then checks whether the currently displayed message is a “operation instruction message to user”, i.e., whether a message for operation instruction is currently displayed, e.g., a message instructing the user to open/close the door of the image printing apparatus  100  because of paper jam or the like, a message notifying the user of an operation sequence, or a message prompting the user to change the operation (B- 3 ) Note that this determination is made by, for example, checking whether or not a help window is stored in advance in correspondence with the currently displayed message. 
   If the “operation instruction message to user” is currently displayed, a help window which is an explanation of the currently displayed “operation instruction message to user” and is information concerning the details of the message is displayed on the operating unit  103  (B- 4 ). The information concerning the details of the message may be stored in the storage unit  102  in advance in correspondence with the message to be read out as needed. 
   If it is determined in step (B- 3 ) that the “operation instruction message to user” is not currently displayed, i.e., a message for which no help function is prepared is currently displayed, a help window as an explanation of the currently displayed window is displayed on the operating unit  103  (B- 5 ). The help window as the explanation of the currently displayed window may be stored in the storage unit  102  in advance in correspondence with the information concerning the currently displayed set window to be read out as needed. 
   The operation of this embodiment in a situation still different from those shown in  FIGS. 5 and 6  will be described next. 
     FIG. 7  is a flow chart showing an example of the operation sequence of help function processing in the image printing apparatus  100  according to the embodiment shown in  FIG. 3 , which is an example still different from those shown in  FIGS. 5 and 6 . 
   The control unit  101  of the image printing apparatus  100  detects that the help key is pressed by the user on the operating unit  103  (C- 1 ). 
   Upon detecting that the help key is pressed by the user, the control unit  101  checks the message currently displayed on the operation panel  115  of the operating unit  103  (C- 2 ). 
   The control unit  101  checks whether the currently displayed message is a “help function effective message”, i.e., whether a message for which a help window is stored in the storage unit  102  of the image printing apparatus  100  in advance in correspondence with the message is currently displayed (C- 3 ). 
   If the “help function effective message” is currently displayed, a help window as an explanation of the currently displayed “help function effective message” is displayed on the operating unit  103  (C- 4 ). The contents to be displayed may be stored in the storage unit  102  in advance to be read out as needed. 
   If the “help function effective message” is not currently displayed, a help window as an explanation of the currently displayed window is displayed on the operating unit  103  (C- 5 ). The contents to be displayed in this case may also be stored in the storage unit  102  in advance to be read out as needed. 
   Specific examples of the display windows to be displayed by the help function of the image printing apparatus  100  of the present invention will be described next with reference to the accompanying drawings. 
     FIG. 8  is a view showing an example of the contents displayed on the operation panel  115  included in the operating unit  103  of the image printing apparatus  100  in  FIG. 3  and a view showing a window for designating a stapling position. 
   The operation panel  115  shown in  FIG. 8  indicates an operation window for allowing the user to select a stapling position when he/she selects stapling processing by means of the postprocessing device  110  of the image printing apparatus  100 . 
   In this specific example, a case will be described, in which the user has selected the designation of “two left positions”, i.e., stapling documents at two left positions, by pressing a button  115   a  on the operation panel  115  in  FIG. 8 . 
     FIG. 9  is a view showing an example of the display contents on the operation panel  115  included in the operating unit  103  of the image printing apparatus  100  according to this embodiment shown in  FIG. 3 , and is a view showing a window for designating a binding direction in double-sided printing. 
   The operation panel  115  shown in  FIG. 9  indicates an operation window for setting/selecting a binding direction in double-sided printing to determine a printing direction on the reverse surface of a sheet in accordance with the binding direction of documents on which images have been printed, when double-sided printing is performed by the image printing apparatus  100 . 
   In this specific example, a case will be described, in which the user selects the designation of “upper binding”, i.e., binding documents at the upper side, by pressing a button  115   b  on the operation panel  115  in  FIG. 9  upon performing the operation in  FIG. 8 . 
   When the operations in  FIGS. 8 and 9  are performed in this manner, the image printing apparatus  100  displays information like that shown in  FIG. 10 . 
     FIG. 10  is a view showing an example of the display contents on the operation panel  115  included in the operating unit  103  of the image printing apparatus  100  according to this embodiment shown in  FIG. 3 , and is a view showing a window to be displayed when the operations shown in  FIGS. 8 and 9  are performed. 
   The message “Please change stapling position or binding direction” is displayed in a display area  115   c  on the operation panel  115  in  FIG. 10 . This is an example of a message for giving the user an operation instruction when image printing cannot be started because the designated stapling position does not match the designated binding direction. 
   With this display alone, the user may not understand the true meaning of the contents displayed in the display area  115   c  or may not know how to cope with the situation. In such a case, when the user presses the help key provided on the operating unit  103 , the window switches to a display window like that shown in  FIG. 11 , and help information corresponding to the message displayed in the display area  115   c  is displayed. 
     FIG. 11  is a view showing an example of the display contents on the operation panel  115  included in the operating unit  103  of the image printing apparatus  100  of the present invention shown in  FIG. 3 , and is a view showing the display window to be displayed when the help key is pressed in the state shown in  FIG. 10 . 
   In the image printing apparatus  100 , when “upper binding” is designated as shown in  FIG. 9 , an image is intentionally printed upside down on the reverse surface of each sheet so that the images on the obverse and reverse surfaces of each double-sided printed sheet can be easily read when the sheets are bound at the upper side. If, however, sheets are stapled at “two left positions” as in the case shown in  FIG. 8 , it is very difficult for the user to read the images printed on the obverse surfaces normally and printed on the reverse surfaces upside down. For this reason, the image printing apparatus  100  displays a message like the one displayed in the display area  115   c  shown in  FIG. 10 . 
   In such a situation, with the message in the display area  115   c  shown in  FIG. 10  alone, the user may be confused as to what to do. In this embodiment, therefore, when the user presses the help key, a window like the one shown in  FIG. 11  is displayed to give the user more detailed information. 
   As described above, according to this embodiment, the image printing apparatus  100  can display help information concerning a displayed message, thus providing more detailed information for the user. 
   If help windows are not prepared for all the display messages, it is preferable to allow the user to recognize a given message as a message for which a help window is prepared.  FIG. 12  shows such a case. 
   In the case shown in  FIG. 12 , “Please change stapling position or binding direction” is displayed in the display area  115   c,  and “see HELP” is additionally written in the display area  115   c  to inform the user that this message is a message for which a help window is prepared. This is an embodiment of the above “identification information allowing the user to identify each of a plurality of messages displayed by the operating unit as a message for which whether or not the details of the message can be displayed by the help function. This makes it possible to clearly inform the user of the presence/absence of a help window. 
   If a given message is a message for which no help window is prepared, the message can be displayed without adding “see HELP”, as shown in  FIG. 10 . When the help key is pressed while a message for which no help window is prepared is displayed, a help window as detailed information of the currently displayed setting window is preferably displayed, as shown in  FIG. 13 .