Patent Publication Number: US-2009219246-A1

Title: Terminal device, terminal system and computer-readable recording medium recording program

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based on and claims the benefit of priority from Japanese Patent Application No. 2008-050859 filed on Feb. 29, 2008; the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present invention relates to a terminal device, and more particularly to a terminal device which includes a display part having a display region whose long-side length and a short-side length differ from each other, and an operation part which is arranged along at least one side of the display region. 
     2. Description of the Related Art 
     Conventionally, there has been known a terminal device which includes a display part for displaying an image, an operation part which is operable by a user, and a control part which controls displaying of an image on the display part in response to an operation of the operation part. Particularly, a portable terminal device such as a mobile phone or a PDA (Personal Digital Assistant) is popularly used because of handiness thereof. 
     In such a terminal device, an operation button switch is arranged in the vicinity of a display region of a display part in general. However, recently, a terminal device having a display region formed of a touch panel has been developed. 
     To enhance the operability of such a terminal device having the display region formed of the touch panel, for example, JP-A-8-221365 discloses a terminal device capable of setting a dominant hand. In such a terminal device, in inputting instructions with a pen using a right hand, a scroll bar is displayed on a right side of the terminal device, while in inputting instructions with a pen using a left hand, the scroll bar is displayed on a left side of the terminal device so that the position of the operation is changed depending on the dominant hand of a user thus enhancing operability of the terminal device. 
     SUMMARY 
     In the above-mentioned terminal device, a user is requested to change a holding mode depending on whether an image to be displayed is a longitudinally elongated image or a laterally elongated image or depending on whether the terminal device is held in the longitudinal direction or in the lateral direction. In such a case, there exists possibility that the scroll bar or the like is displayed in the direction different from a user&#39;s side depending on the dominant hand of the user and hence, it is difficult for the user to operate the terminal device, and this difficulty in operation may cause an erroneous operation. 
     The present invention has been made to overcome the above-mentioned drawbacks, and it is an object of the present invention to provide a terminal device, a terminal system and a recording medium which records programs of the computer which can enhance operability of an operation part corresponding to an operation mode such as set dominant hand information or image-kind information indicative of a kind of an image to be displayed. 
     To achieve the above-mentioned object, according to one aspect of the present invention, there is provided a terminal device which includes: a housing; an image data memory part which is configured to store image data; a display part which is mounted on the housing and has a display region whose long-side length and short-side length differ from each other; a display control part which is configured to perform a control of displaying an image on the display region based on the image data in the image data memory part; and an operation part which is mounted on at least one end of the housing, is arranged along at least one side of the display region, and is configured to be operable by a user, wherein the operation part includes an operation mode setting part which is configured to set either one of a right-hand operation mode in which the operation part is operated by a right hand of the user and a left-hand operation mode in which the operation part is operated by a left hand of the user, the image data memory part is configured to store, as image kind information, either one of first-kind image information which allows the user to observe the image in a holding mode in which the operation part is positioned on either one of left and right sides of the housing and second-kind image information which allows the user to observe the image in a holding mode in which the operation part is positioned on a deep side of the housing corresponding to the respective image data; the display control part is, in a state in which the image kind information which corresponds to the image data of an image to be displayed on the display region is the first-kind image information and the right-hand operation mode is set by the operation mode setting part, configured to perform a control of displaying the image at an angle which allows the user to observe the image in the holding mode in which the operation part is positioned on a right side of the housing, the display control part is, in a state in which the image kind information which corresponds to the image data of an image to be displayed on the display region is the first-kind image information and the left-hand operation mode is set by the operation mode setting part, configured to perform a control of displaying the image at an angle which allows the user to observe the image in the holding mode in which the operation part is positioned on a left side of the housing, and the display control part is, in a state in which the image kind information which corresponds to the image data of an image to be displayed on the display region is the second-kind image information and either one of the left-hand operation mode and the right-hand operation mode is set by the operation mode setting part, configured to perform a control of displaying the image at an angle which allows the user to observe the image in the holding mode in which the operation part is positioned on a user&#39;s side of the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory view showing a terminal device according to one embodiment of the present invention; 
         FIG. 2  is an explanatory view showing a terminal device according to one embodiment of the present invention; 
         FIG. 3  is an explanatory view showing a terminal device according to one embodiment of the present invention; 
         FIG. 4  is an explanatory view showing a terminal device according to one embodiment of the present invention; 
         FIG. 5  is a block diagram showing a terminal device according to one embodiment of the present invention; 
         FIG. 6  is a functional block diagram showing the terminal device and a personal computer according to one embodiment of the present invention; 
         FIG. 7  is an explanatory view showing a set data table in the terminal device according to one embodiment of the present invention; 
         FIG. 8  is an explanatory view showing a raster data setting table in the terminal device according to one embodiment of the present invention; 
         FIG. 9  is an explanatory view showing a key assignment setting table in the terminal device according to one embodiment of the present invention; 
         FIG. 10  is a flowchart showing control processing executed in the terminal device according to one embodiment of the present invention; 
         FIG. 11  is a flowchart showing control processing executed in the terminal device according to one embodiment of the present invention; 
         FIG. 12  is a flowchart showing control processing executed in the terminal device according to one embodiment of the present invention; 
         FIG. 13  is an explanatory view showing the terminal device according to one embodiment of the present invention; 
         FIG. 14  is an explanatory view showing a key assignment setting table in the terminal device according to one embodiment of the present invention; 
         FIG. 15  is a flowchart showing control processing executed in the terminal device according to one embodiment of the present invention; 
         FIG. 16  is an explanatory view showing a terminal device according to one embodiment of the present invention; 
         FIG. 17  is an explanatory view showing a terminal device according to one embodiment of the present invention; 
         FIG. 18  is an explanatory view showing a key assignment setting table in the terminal device according to one embodiment of the present invention; 
         FIG. 19  is a flowchart showing control processing executed in the terminal device according to one embodiment of the present invention; and 
         FIG. 20  is an explanatory view showing a terminal device according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Preferred embodiments of the present invention are explained hereinafter in conjunction with attached drawings. 
     [1. Constitution or the Like of Terminal Device] 
     First of all, the schematic constitution or the like of a terminal device  10  is explained in conjunction with  FIG. 1 . 
       FIG. 1  is a view showing an example of the schematic constitution of the terminal device  10  according to this embodiment. As shown in  FIG. 1(A) , the terminal device  10  according to this embodiment is a device which exhibits high portability, and also is a device which displays raster data such as various image data. Further, the terminal device  10  is constituted of a housing  12 , a display device  14  and a cross button switch  16 . 
     The housing  12  is formed in a rectangular shape, and the display device  14  is arranged at the center of the housing  12 . Further, the cross button switch  16  is arranged at one end of the housing  12 . 
     The display device  14  is arranged at the center of the housing  12 . The display device  14  has a rectangular display region  14   a  where a longitudinal length and a lateral length differ from each other. That is, the display device  14  which constitutes a display part is mounted on the housing  12 , and has the display region  14   a  where a length of long sides and the length of short sides differ from each other. 
     The cross button switch  16  constitutes an operation part which is operable by a user. The cross button switch  16  is arranged at least one end of the housing  12  and, at the same time, the cross button switch  16  is arranged along at least one side of the display region  14   a  of the display device  14 . The cross button switch  16  is a cross operation part which is operable in upper, lower, left and right directions (crosswise directions) The cross button switch  16  is, as shown in  FIG. 1(B) , constituted of a left button switch portion  16   a , an upper button switch portion  16   b , a right button switch portion  16   c  and a lower button switch portion  16   d . The cross button switch  16  is capable of performing plural kinds of operations corresponding to operation modes of the user. Although the cross button switch  16  is arranged along one long side of the display region  14   a  in this embodiment, the present invention is not limited to such an arrangement of the cross button switch  16 . 
     The display modes and the operation modes controlled by the above-mentioned terminal device  10  are explained hereinafter in conjunction with  FIG. 2  to  FIG. 4 . 
     Further, with respect to this terminal device  10 , by rotating the housing  12  in conformity with a direction of an image, the terminal device  10  is arranged in a direction which allows a user to easily observe the image. Further, it is possible to set the dominant hand setting to a right hand or a left hand of the user. The direction of the image may also be changed by such setting. Still further, the direction of the image is also changed depending on whether the direction of the image is for portrait or landscape. “Portrait” is a longitudinally-elongated image, and “landscape” is a laterally-elongated image. 
     To be more specific, when the left-hand operation is set and the image to be displayed is the portrait image, as shown in  FIG. 2(A) , the image is displayed to allow the user to observe the image from a user&#39;s side in a holding mode in which the cross button switch  16  is arranged on a left side of the housing  12 . 
     Further, when the right-hand operation is set and the image to be displayed is the portrait image, as shown in  FIG. 2(B) , the image is displayed to allow the user to observe the image from a user&#39;s side in a holding mode in which the cross button switch  16  is arranged on a right side of the housing  12 . 
     Further, when the image to be displayed is the landscape image, irrespective of setting of a dominant hand, as shown in  FIG. 2(C) , the image is displayed in a direction (at an angle) which allows the user to observe the image in a holding mode in which the cross button switch  16  is positioned on a user&#39;s side of the housing  12 . 
     By displaying the image in such a manner, the image is displayed at the angle corresponding to the operation mode. This angle is determined based on the operation mode indicative of the dominant hand or the like and the orientation information (image kind information) of the image having different longitudinal and lateral lengths. Particularly, this angle is an angle at which the operation part is positioned on either one of left and right sides or the user&#39;s side. Due to such constitution, it is possible to prevent the operation part from being positioned on a deep side of the display region thus enhancing the operability of the terminal device  10 . 
     Further, the cross button switch  16  is provided with a key assignment function which allocates the respective button switch portions corresponding to operations. The key assignment function of the cross button switch  16  is changed depending on setting of the dominant hand and a kind (portrait, landscape) of the image. 
     To be more specific, when the right-hand operation is set and the image to be displayed is the portrait image, as shown in  FIG. 3(A) , a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d . Then, when the cross button switch  16  is operated in the left direction (the left direction as viewed from a user&#39;s side, expressed in the same manner hereinafter also with respect to the upper direction, the right direction and the lower direction) by the user, the previous page is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the right direction by the user, the next page is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next document is displayed. 
     Then, when the setting of operation is changed from the right-hand operation to the left-hand operation, as shown in  FIG. 3(B) , the image per se is rotated by 180 degrees. Further, the next page is assigned to the left button switch portion  16   a , the next document is assigned to the upper button switch portion  16   b , the previous page is assigned to the right button switch portion  16   c , and the previous document is assigned to the lower button switch portion  16   d . Due to such operations, to allow the user to observe the image, as shown in  FIG. 3(C) , the housing  12  is rotated by 180 degrees. Further, the terminal device  10  assumes a holding mode in which the cross button switch  16  is positioned on a left side of the housing  12 . Then, when the cross button switch  16  is operated in the left direction by the user, the previous page is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the right direction by the user, the next page is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next document is displayed. 
     Further, in case the right-hand operation is set and the image to be displayed is the landscape image, as shown in  FIG. 3(D) , when the cross button switch  16  is operated in the left direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous page is displayed, when the cross button switch  16  is operated in the right direction by the user, the next document is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next page is displayed. Further, when the left-hand operation is set and the image to be displayed is the landscape image, as shown in  FIG. 3(E) , a key assignment function equal to the key assignment function set at the time of performing the right-hand operation is given to the cross button switch  16 . 
     Further, when the left-hand operation is set and the image to be displayed is the portrait image, as shown in  FIG. 4(A) , the next page is assigned to the left button switch portion  16   a , the next document is assigned to the upper button switch portion  16   b , the previous page is assigned to the right button switch portion  16   c , and the previous document is assigned to the lower button switch portion  16   d . Then, when the cross button switch  16  is operated in the left direction by the user, the previous page is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the right direction by the user, the next page is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next document is displayed. 
     Then, when the image to be displayed is changed to the landscape, as shown in  FIG. 4(B) , the image per se is rotated by 90 degrees. Further, the previous page is assigned to the left button switch portion  16   a , and the next page is assigned to the right button switch portion  16   c . Due to such operations, to allow the user to observe the image, as shown in  FIG. 4(C) , the housing  12  is rotated by −90 degrees. Further, the terminal device  10  assumes a holding mode in which the cross button switch  16  is positioned on a user&#39;s side of the housing  12 . Then, when the cross button switch  16  is operated in the left direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous page is displayed, when the cross button switch  16  is operated in the right direction by the user, the next document is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next page is displayed. 
     Further, when the right-hand operation is set and the image to be displayed is the portrait image, as shown in  FIG. 4(D) , the previous page is assigned to the left button switch portion  16   a , the previous document is assigned to the upper button switch portion  16   b , the next page is assigned to the right button switch portion  16   c , and the next document is assigned to the lower button switch portion  16   d . Then, when the cross button switch  16  is operated in the left direction by the user, the previous page is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the right direction by the user, the next page is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next document is displayed. 
     Then, when the image to be displayed is changed to the landscape, as shown in  FIG. 4(E) , the image per se is rotated by −90 degrees. Further, the next document is assigned to the upper button switch portion  16   b , and the previous document is assigned to the lower button switch portion  16   d . Due to such operations, to allow the user to observe the image, as shown in  FIG. 4(F) , the housing  12  is rotated by 90 degrees. Further, the terminal device  10  assumes a holding mode in which the cross button switch  16  is positioned on a user&#39;s side of the housing  12 . Then, when the cross button switch  16  is operated in the left direction by the user, the previous document is displayed, when the cross button switch  16  is operated in the upper direction by the user, the previous page is displayed, when the cross button switch  16  is operated in the right direction by the user, the next document is displayed and when the cross button switch  16  is operated in the lower direction by the user, the next page is displayed. 
     By changing the key assignment in this manner, it is possible to perform the assignment of control contents corresponding to kinds of images (image kind information such as portrait, landscape and the like) and the operation modes and hence, the control of the terminal device  10  can be simplified. Further, the user can operate the terminal device  10  without being conscious of the holding mode and hence, the operability of the terminal device  10  can be enhanced. 
     [2. Explanation of Constitution or the Like of Terminal Device  10 ] 
     Next, the constitution and the manner of operation of the terminal device  10  are explained in conjunction with  FIG. 5 . 
       FIG. 5  shows an example of the schematic constitution of the terminal device  10  of this embodiment. A general-type portable computer is applicable to the terminal device  10  and, as shown in  FIG. 5 , the terminal device  10  is constituted of a CPU (Central Processing Unit)  20 , a ROM (Read Only Memory)  21 , a RAM (Random Access Memory)  22 , an EEPROM (Electrically Erasable and Programmable Read Only Memory)  23 , an inputting part  24 , a display part  25 , a communication part  26  and a memory card interface (a memory card I/F)  27 . These respective constitutional elements are connected with each other via a system bus. 
     The CPU  20  functions as various units in accordance with various programs and controls the terminal device  10 . Various programs and the like are recorded (stored) in the ROM  21 . The RAM  22  is a storage medium which temporarily stores various data and the like. The EEPROM  23  is a storage medium which can store data and, at the same time, can electrically erase the stored data. The inputting part  24  controls an inputting unit such as the cross button switch  16  capable of inputting predetermined information. The display part  25  is constituted of the display device  14  and the like which displays an image. The communication part  26  performs communication between the terminal device  10  and other devices such as a personal computer (PC in the drawing)  31  and a printer  32 . The memory card interface  27  performs communication between the terminal device  10  and a memory card  33 . 
       FIG. 6  is a functional block diagram for forming an image using the terminal device  10  of this embodiment and the personal computer  31 . 
     The personal computer  31  includes, as shown in  FIG. 6 , a control part  40  which is constituted of a CPU, a ROM, a RAM and the like. Further, the control part  40  outputs rendered image data to an output device  44  in accordance with application program  41 , a GDI (Graphics Device Interface)  42  and a printer driver program  43 . In this embodiment, the terminal device  10  includes the output device  44 . Here, the printer driver program  43  is stored in the RAM of the personal computer  31  via a storage medium drive of the personal computer  31  not shown in the drawing. 
     The control part  40 , upon receiving display instruction of raster data based on the application program  41 , receives printing setting, printing data, orientation information and the like from the application program  41  via the GDI  42 . Then, the control part  40  renders the printing data in accordance with the printer driver program  43  and forms image data. Then, the control part  40  outputs image data to the output device  44  in association with the orientation information indicative of kind of image in accordance with the printer driver program  43 . 
     In this manner, the personal computer  31  outputs the orientation information (image kind information) indicative of kinds of images to the terminal device  10  in a form that the orientation information is added to the image data. Accordingly, by merely outputting the image data to the terminal device  10  from the personal computer  31 , it is possible to easily form the image data to be used in the terminal device  10 . 
     (Set Data Table) 
     The set data table which is stored in the EEPROM  23  of the terminal device  10  having the above-mentioned constitution is explained in conjunction with  FIG. 7 . Even when the set data table explained hereinafter is not stored in the EEPROM  23 , it is sufficient that data and program having such functions are stored in the EEPROM  23 . 
     The set data table stored in the EEPROM  23  is the table which stores set data relating to raster data to be displayed or set data relating to a dominant hand. In the set data table, as shown in  FIG. 7 , a page ID and a document ID of raster data to be displayed and setting of the dominant hand are stored in a correlated manner. 
     By referencing such a set data table, the document and the page to be displayed and setting of the dominant hand to be set can be recognized. 
     (Raster Data Setting Table) 
     The raster data setting table stored in the EEPROM  23  of the terminal device  10  having the above-mentioned constitution is explained in conjunction with  FIG. 8 . Even when the raster data setting table explained hereinafter is not stored in the EEPROM  23 , it is sufficient that data and programs having such functions are stored in the EEPROM  23 . 
     The raster data setting table stored in the EEPROM  23  is a table in which data relating to a displayable raster data is set. In the raster data setting table, as shown in  FIG. 8 , a document ID, a page ID, raster data and orientation information (for example, portrait, landscape or the like) are correlated to each other. The document ID is information which enables identification of a document on raster data. The page ID is information which enables identification of a page of raster data in such a document ID. Further, raster data includes file names indicative of raster data, addresses and the like, and raster data per se is also stored in the EEPROM  23  per se. Further, orientation information is information which enables the identification whether the raster data is data on the longitudinally-elongated portrait image or data on the laterally-elongated landscape image. 
     By referencing this raster data setting table, it is possible to recognize the raster data per se or the orientation information of the raster data or the like. The EEPROM  23  functions as an image data memory part. That is, in the EEPROM  23 , either one of the portrait image and the landscape image is stored as the orientation information (image kind information) corresponding to each image data. Further, the portrait image (longitudinally-elongated image data, the first kind image information) is an image which is observed by the user in a holding mode in which the cross button switch  16  (operation part, cross operation part) is positioned on a left or right side of the housing  12 . On the other hand, the landscape image (laterally-elongated image data, the second kind image information) is an image which is observed by the user in a holding mode in which the cross button switch  16  is positioned on a deep side of the housing  12 . 
     (Key Assignment Setting Table) 
     The key assignment setting table stored in the EEPROM  23  of the terminal device  10  having the above-mentioned constitution is explained in conjunction with  FIG. 9 . Even when the key assignment setting table explained hereinafter is not stored in the EEPROM  23 , it is sufficient that data and programs having such functions are stored in the EEPROM  23 . 
     The key assignment setting table stored in the EEPROM  23  is a table which shows key assignment in using the cross button switch  16 . In the key assignment setting table, as shown in  FIG. 9 , the orientation information, dominant hand setting and kinds of keys are stored in a correlated manner. 
     To be more specific, when the orientation information is portrait and dominant hand setting is set as a right hand, a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d . On the other hand, when the orientation information is portrait and dominant hand setting is set as a left hand, a next page is assigned to the left button switch portion  16   a , a next document is assigned to the upper button switch portion  16   b , a previous page is assigned to the right button switch portion  16   c , and a previous document is assigned to the lower button switch portion  16   d . When the orientation information is a landscape, irrespective of whether the dominant hand setting is set as the right hand or the left hand, a next page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a previous page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d.    
     In this manner, the assignment of control contents corresponding to the operation directions of the cross button switch  16  (cross operation part) is performed based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Accordingly, the assignment of control contents corresponding to the image kind information and the operation mode can be performed thus simplifying the operation of the terminal device  10 . Further, when the orientation information (image kind information) corresponding to the image data of an image to be displayed on the display region  14   a  is a portrait, irrespective of dominant hand setting (operation mode), the control content corresponding to the operation direction of the cross button switch  16  (cross operation part) becomes the same. Accordingly, the user can operate the terminal device  10  without being conscious of the holding mode of the terminal device  10  and hence, the operability of the terminal device  10  can be enhanced. 
     [3. Operation of Terminal Device  10 ] 
     The detailed operation of the terminal device  10  is further specifically explained hereinafter using flowcharts. 
     (Explanation of Main Processing Flow of Terminal Device  10 ) 
     First of all, the further specific operations of the terminal device  10  are explained in conjunction with  FIG. 10 .  FIG. 10  is a flowchart showing the entire processing of the terminal device  10 . 
     First of all, as shown in  FIG. 10 , when a power source of the terminal device  10  is turned on, the CPU  20  executes initial setting processing such as the permission of access to the ROM  21 , the RAM  22  and the EEPROM  23 , initializing of working areas and the like. Thereafter, the CPU  20  sets “1” to a document ID which is positioned in a predetermined area of the EEPROM  23  and also sets “1” to a page ID indicative of a page to be displayed which is positioned in a predetermined area of the EEPROM  23  and, at the same time, the dominant hand setting is set as the right hand (step S 91 ). That is, the CPU  20  functions as the operation mode setting part and sets either one of the right-hand operation mode in which the cross button switch  16  is operated by a right hand of a user and the left-hand operation mode in which the cross button switch  16  is operated by a left hand of the user. When the processing in step S 91  is finished, the processing advances to step S 92 . 
     In step S 92 , the CPU  20  determines whether or not the display updating is required. In this processing, the CPU  20  determines whether or not the display updating is required based on whether or not any one of a first condition that the initial setting processing is performed, a second condition that the page is turned over and a third condition that dominant hand setting is changed is satisfied. When the CPU  20  determines that the display updating is required (step S 92 : Yes), although explained in detail later in conjunction with  FIG. 11 , the CPU  20  executes the display updating processing for updating the display (step S 93 ), and the processing advances to step S 101 . On the other hand, when the CPU  20  determines that the display updating is not required (step S 92 : No), the processing advances to step S 101  without executing processing in step S 93 . 
     In step S 101 , the CPU  20  determines whether or not the next page operation is performed. In this processing, the CPU  20  references the set data table positioned in the predetermined region of the EEPROM  23  (see  FIG. 7 ) and the raster data setting table (see  FIG. 8 ), and reads out the orientation information on raster data corresponding to a current document ID and a current page ID and data on dominant hand setting. Then, the CPU  20  references the key assignment setting table (see  FIG. 9 ) positioned in a predetermined area of the EEPROM  23  and reads out the key assignment information corresponding to the orientation information and the dominant hand setting. Then, the CPU  20  determines whether or not the next page operation is performed based on whether or not the key corresponding to the next page in the key assignment is operated. Further, also in step S 106 , step S 111 , step S 116  described in detail later, the CPU  20  references the table in the same manner. Then, the CPU  20  reads out the key assignment information corresponding to the orientation information and the dominant hand setting, and performs various determinations corresponding to the key assignment. 
     When the CPU  20  determines that the next page operation is performed (step S 101 : YES), the CPU  20  determines whether or not the raster data currently displayed on the display region  14   a  is of a last page in the same document (step S 102 ). When the CPU  20  determines that the raster data is not of the last page (step S 102 : NO), the page ID is incremented by “1” (step S 103 ). Further, when the CPU  20  determines that the raster data is of the last page (step S 102 : YES), the processing advances to step S 130  without executing processing in step S 103 . On the other hand, when the CPU  20  determines that the next page operation is not performed (step S 101 : NO), the processing advances to step S 106 . 
     In step S 106 , the CPU  20  determines whether or not the previous page operation is performed. In this processing, the CPU  20  reads out the key assignment information corresponding to the orientation information and the dominant hand setting. Then, the CPU  20  determines whether or not the previous page operation is performed based on whether or not the key corresponding to the previous page in the key assignment is operated. When the CPU  20  determines that the previous page operation is performed (step S 106 : YES), the CPU  20  determines whether or not the raster data currently displayed on the display region  14   a  is of a first page in the same document (step S 107 ). When the CPU  20  determines that the raster data is not of the first page (step S 107 : NO), the page ID is decremented by “1” (step S 108 ). Further, when the CPU  20  determines that the raster data is of the first page (step S 107 : YES), the processing advances to step S 130  without executing processing in step S 108 . On the other hand, when the CPU  20  determines that the previous page operation is not performed (step S 106 : NO), the processing advances to step S 111 . 
     In step S 111 , the CPU  20  determines whether or not the next document operation is performed. In this processing, the CPU  20  reads out the key assignment information corresponding to the orientation information and the dominant hand setting. Then, the CPU  20  determines whether or not the next document operation is performed based on whether or not the key corresponding to the next document in the key assignment is operated. When the CPU  20  determines that the next document operation is performed (step S 111 : YES), the CPU  20  determines whether or not the raster data currently displayed on the display region  14   a  is of a last document in a document list (step S 112 ). Further, when the CPU  20  determines that the raster data is not of the last document in the document list (step S 112 : NO), the document ID is incremented by “1” and, at the same time, the page ID is set to “1” (step S 113 ). When the CPU  20  determines that the raster data is of the last document in the document list (step S 112 : YES), the processing advances to step S 130  without executing processing in step S 113 . On the other hand, when the CPU  20  determines that the next document operation is not performed (step S 111 : NO), the processing advances to step S 116 . 
     In step S 116 , the CPU  20  determines whether or not the previous document operation is performed. In this processing, the CPU  20  reads out the key assignment information corresponding to the orientation information and the dominant hand setting. Then, the CPU  20  determines whether or not the previous document operation is performed based on whether or not the key corresponding to the previous document in the key assignment is operated. When the CPU  20  determines that the previous document operation is performed (step S 116 : YES), the CPU  20  determines whether or not the raster data currently displayed on the display region  14   a  is of a head document in a document list (step S 117 ). When the CPU  20  determines that the raster data is not of the head document in the document list (step S 117 : NO), the document ID is decremented by “1” and, at the same time, the page ID is set to “1” (step S 118 ). When the CPU  20  determines that the raster data is of the head document in the document list (step S 117 : YES), the processing advances to step S 130  without executing processing in step S 118 . On the other hand, when the CPU  20  determines that the head document operation is not performed (step S 116 : NO), the processing advances to step S 121 . 
     In step S 121 , the CPU  20  determines whether or not a dominant hand setting change operation is performed. In this processing, when the CPU  20  determines that the dominant hand setting change operation is performed (step S 121 : YES), the CPU  20  determines whether or not the current dominant hand setting is set as the right hand (step S 122 ). When the CPU  20  determines that the current dominant hand setting is set as the right hand (step S 122 : YES), the dominant hand setting is changed to the left hand (step S 124 ). Further, when the CPU  20  determines that the current dominant hand setting is the left hand (step S 122 : NO), the dominant hand setting is changed to the right hand (step S 123 ), and the processing advances to step S 130 . The CPU  20  functions as an operation mode setting part. That is, the CPU  20  sets either one of the right-hand operation mode in which the cross button switch  16  is operated by a right hand of a user and the left-hand operation mode in which the cross button switch  16  is operated by a left hand of the user. On the other hand, when the CPU  20  determines that the dominant hand setting change operation is not performed (step S 121 : NO), the processing advances to step S 130  without executing processing in step S 122  to step S 124 . 
     In step S 130 , the CPU  20  determines whether or not the power source is turned off. In this processing, when the CPU  20  determines that the power source is turned off (step S 130 : YES), the main processing is finished. On the other hand, when the CPU  20  determines that the power source is not turned off (step S 130 : NO), the processing advances to step S 101 . 
     (Explanation of Display Updating Processing Flow of Terminal Device  10 ) 
     A subroutine executed in step S 93  shown in  FIG. 10  is explained in conjunction with  FIG. 11 . 
     Firstly, as shown in  FIG. 11 , the CPU  20  determines whether or not the orientation information corresponding to the current page is of a portrait (step S 151 ). In this processing, the CPU  20  references the raster data setting table (see  FIG. 8 ), and reads out the orientation information stored corresponding to the raster data which is to be subject to display updating. Then, the CPU  20  determines whether or not the orientation information corresponding to the current page is of the portrait. When the CPU  20  determines that the orientation information corresponding to the current page is of the portrait (step S 151 : YES), the processing advances to step S 152 . On the other hand, when the CPU  20  determines that the orientation information corresponding to the current page is of a landscape (step S 151 : NO), the processing advances to step S 153 . 
     In step S 152 , the CPU  20  determines whether or not dominant hand setting is set as the right hand. In this processing, the CPU  20  references the set data table (see  FIG. 7 ), and reads out dominant hand setting, and determines whether or not dominant hand setting is set as the right hand. 
     When the CPU  20  determines that dominant hand setting is set as the right hand (step S 152 : YES), the CPU  20  performs setting of button switches such that a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d  (step S 161 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs the assignment of control contents corresponding to operation directions of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Further, the CPU  20  performs a control of keeping display of raster data on a predetermined page in a designated document (step S 162 ), and the main subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a portrait (first kind image information), when the dominant hand setting is set as the right hand (the right-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a right side of the housing  12 . 
     On the other hand, when the CPU  20  determines that dominant hand setting is set as the left hand (step S 152 : NO), the CPU  20  performs setting of button switches such that a next page is assigned to the left button switch portion  16   a , a next document is assigned to the upper button switch portion  16   b , a previous page is assigned to the right button switch portion  16   c , and a previous document is assigned to the lower button switch portion  16   d  (step S 163 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs the assignment of control contents corresponding to operation directions of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Further, the CPU  20  performs a control of displaying of raster data on a predetermined page of a designated document by rotating 180 degrees (step S 164 ), and the main subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a portrait (first kind image information), when the dominant hand setting is set as the left hand (the left-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a left side of the housing  12 . 
     Further, in step S 153 , the CPU  20 , in the same manner as the above-mentioned step S 152 , determines whether or not dominant hand setting is set as the right hand. 
     When the CPU  20  determines that dominant hand setting is set as the right hand (step S 153 : YES), the CPU  20  performs setting of button switches such that a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d  (step S 165 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs the assignment of control contents corresponding to operation directions of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Further, the CPU  20  performs a control of keeping display of raster data on a predetermined page in a designated document (step S 166 ), and the main subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a landscape (second kind image information), when the dominant hand setting is set as the right hand (the right-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part, cross operation part) is positioned on a user&#39;s side of the housing  12 . 
     On the other hand, when the CPU  20  determines that dominant hand setting is set as the left hand (step S 153 : NO), the CPU  20  performs setting of button switches such that a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d  (step S 167 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs the assignment of control contents corresponding to operation directions of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Further, the CPU  20  performs a control of keeping display of raster data on a predetermined page in a designated document (step S 166 ), and the main subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a landscape (second kind image information), when the dominant hand setting is set as the left hand (the left-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a left side of the housing  12 . 
     In this manner, by displaying the image at the angle which makes the operation part positioned on a left or right side or a user&#39;s side corresponding to the operation mode based on the operation mode indicative of the dominant hand or the like and the image kind information of the image which displays an image having different longitudinal and lateral lengths or the like, it is possible to prevent the operation part from being positioned on a deep side of the display region thus enhancing the operability of the terminal device  10 . Further, by assigning the control contents corresponding to the image kind information and the operation modes, the operation of the terminal device  10  can be simplified. 
     (Explanation of Processing Flow in Accordance with Printer Driver Program  43  in Personal Computer  31 ) 
     Processing in accordance with a printer driver program  43  in the personal computer  31  is explained hereinafter in conjunction with  FIG. 12 . 
     Firstly, as shown in  FIG. 12 , the control part  40  which performs a control in accordance with the printer driver program  43  receives printing setting, printing data and the orientation information from the GDI  42  (step S 201 ). Then, the control part  40  renders the printing data with received resolution at a starting position (step S 202 ), and outputs the rendered raster data to the output device (step S 203 ). Subsequently, the control part  40  reads out the orientation information corresponding to the raster data, and determines whether or not the orientation information is a portrait (step S 204 ). When the control part  40  determines that the orientation information is the portrait (step S 204 : YES), the control part  40  outputs data in a form that the data outputted from the output device is associated with the portrait (step S 205 ). When the control part  40  determines that the orientation information is a landscape (step S 204 : NO), the control part  40  outputs the data in a form that the landscape is associated with the data outputted from the output device (step S 206 ). Then, this processing is finished. 
     In this manner, the personal computer  31  outputs the image data (raster image data) of the image to be displayed on the display region  14   a  of the terminal device  10  to the terminal device  10  in a form that the image kind information (orientation information) is added to the image data (raster data). Accordingly, by merely outputting the image data to the terminal device  10  from the personal computer  31 , it is possible to easily form the image data used by the terminal device  10 . 
     In the above-mentioned embodiment, when the orientation information is the portrait, the key assignment is performed such that the control contents corresponding to the operation direction of the cross button switch  16  become the same between a case in which the dominant hand setting is set as the right hand and the terminal device  10  is held such that the cross button switch  16  is positioned on a right side of the housing  12  and a case in which the dominant hand setting is set as the left hand and the terminal device  10  is held such that the cross button switch  16  is positioned on a left side of the housing  12 . However, the present invention is not limited to such key assignment. For example, when the orientation information is the landscape, the key assignment may be performed such that the control contents corresponding to the operation direction of the cross button switch  16  become the same between a case in which the dominant hand setting is set as the right hand and the terminal device  10  is held such that the cross button switch  16  is positioned on a user&#39;s side of the housing  12  and a case in which the dominant hand setting is set as the left hand and the terminal device  10  is held such that the cross button switch  16  is positioned on a user&#39;s side of a housing  12 . 
     Second Embodiment 
     One specific embodiment of the terminal device  10  is explained hereinafter in conjunction with  FIG. 13  to  FIG. 15 . For facilitating the understanding of the invention, technical features different from the above-mentioned embodiment are explained in detail and the explanation of the same technical features is omitted. 
     When a left-hand operation is set and an image to be displayed is a portrait image, as shown in  FIG. 13(A) , a next page is assigned to the left button switch portion  16   a , a next document is assigned to the upper button switch portion  16   b , a previous page is assigned to the right button switch portion  16   c , and a previous document is assigned to the lower button switch portion  16   d . Further, the previous page is displayed when the user operates the cross button switch  16  in the left direction, the previous document is displayed when the user operates the cross button switch  16  in the upper direction, the next page is displayed when the user operates the cross button switch  16  in the right direction, and the next document is displayed when the user operates the cross button switch  16  in the lower direction. 
     Then, when the image to be displayed is changed to a landscape, as shown in  FIG. 13(B) , the image per se is rotated by 90 degrees. Further, a previous document is assigned to the left button switch portion  16   a , a next page is assigned to the upper button switch portion  16   b , a next document is assigned to the right button switch portion  16   c , and a previous page is assigned to the lower button switch portion  16   d . Accordingly, when the housing  12  is rotated by −90 degrees as shown in  FIG. 13(C)  for allowing a user to observe the image, the terminal device  10  assumes a holding mode in which the cross button switch  16  is positioned on a user&#39;s side of the housing  12 . Then, the previous page is displayed when the user operates the cross button switch  16  in the left direction, the previous document is displayed when the user operates the cross button switch  16  in the upper direction, the next page is displayed when the user operates the cross button switch  16  in the right direction, and the next document is displayed when the user operates the cross button switch  16  in the lower direction. 
     Further, when a right-hand operation is set and an image to be displayed is a portrait image, as shown in  FIG. 13(D) , a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d . Further, the previous page is displayed when the user operates the cross button switch  16  in the left direction, the previous document is displayed when the user operates the cross button switch  16  in the upper direction, the next page is displayed when the user operates the cross button switch  16  in the right direction, and the next document is displayed when the user operates the cross button switch  16  in the lower direction. 
     Then, when the image to be displayed is changed to a landscape, as shown in  FIG. 13(E) , the image per se is rotated by −90 degrees. Further, a previous document is assigned to the left button switch portion  16   a , a next page is assigned to the upper button switch portion  16   b , a next document is assigned to the right button switch portion  16   c , and a previous page is assigned to the lower button switch portion  16   d . Accordingly, when the housing  12  is rotated by 90 degrees as shown in  FIG. 13(F)  for allowing a user to observe the image, the terminal device  10  assumes a holding mode in which the cross button switch  16  is positioned on a user&#39;s side of the housing  12 . Then, the previous page is displayed when the user operates the cross button switch  16  in the left direction, the previous document is displayed when the user operates the cross button switch  16  in the upper direction, the next page is displayed when the user operates the cross button switch  16  in the right direction, and the next document is displayed when the user operates the cross button switch  16  in the lower direction. 
     (Key Assignment Setting Table) 
     Further, in the above-mentioned key assignment setting table, as shown in  FIG. 14 , when the orientation information is a portrait and a dominant hand setting is set as a right hand, a previous page is assigned to the left button switch portion  16   a , a previous document is assigned to the upper button switch portion  16   b , a next page is assigned to the right button switch portion  16   c , and a next document is assigned to the lower button switch portion  16   d . Further, when the orientation information is a portrait and a dominant hand setting is set as a left hand, a next page is assigned to the left button switch portion  16   a , a next document is assigned to the upper button switch portion  16   b , a previous page is assigned to the right button switch portion  16   c , and a previous document is assigned to the lower button switch portion  16   d . When the orientation information is a landscape, irrespective of whether the dominant hand setting is set as the right hand or the left hand, a previous document is assigned to the left button switch portion  16   a , a next page is assigned to the upper button switch portion  16   b , a next document is assigned to the right button switch portion  16   c , and a previous page is assigned to the lower button switch portion  16   d.    
     (Explanation of Display Updating Processing Flow of Terminal Device  10 ) 
     A subroutine executed in step S 93  shown in  FIG. 10  is explained in conjunction with  FIG. 15 . 
     As shown in  FIG. 15 , when the CPU  20  determines that the orientation information corresponding to the current page is a landscape (step S 151 : NO) and the dominant hand setting is set as the right hand (step S 153 : YES), button switch setting is performed such that a previous document is assigned to the left button switch portion  16   a , a next page is assigned to the upper button switch portion  16   b , a next document is assigned to the right button switch portion  16   c , and a previous page is assigned to the lower button switch portion  16   d  (step S 175 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs assignment of control contents corresponding to the operation direction of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Then, the CPU  20  performs a control of keeping display of raster data on a predetermined page of a designated document (step S 176 ), and this subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a landscape (second kind image information), when the dominant hand setting is set as the right hand (the right-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a user&#39;s side of the housing  12 . 
     Further, when the CPU  20  determines that the orientation information corresponding to the current page is a landscape (step S 151 : NO) and the dominant hand setting is set as the left hand (step S 153 : NO), button switch setting is performed such that a previous document is assigned to the left button switch portion  16   a , a next page is assigned to the upper button switch portion  16   b , a next document is assigned to the right button switch portion  16   c , and a previous page is assigned to the lower button switch portion  16   d  (step S 177 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs assignment of control contents corresponding to the operation direction of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Then, the CPU  20  performs a control of keeping display of raster data on a predetermined page of a designated document (step S 178 ), and this subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a landscape (second kind image information), when the dominant hand setting is set as the left hand (the left-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a user&#39;s side of the housing  12 . 
     By changing the key assignment in this manner, the CPU  20  can perform the assignment of control content corresponding to the kind of the image (image kind information such as portrait or landscape) and the operation mode thus simplifying the control of the terminal device  10 . Further, the user can operate the terminal device  10  without being conscious of the holding mode and hence, operability of the terminal device  10  can be enhanced. Further, the control contents corresponding to the operation direction of the cross button switch  16  become the same between the case in which the orientation information (image kind information) corresponding to the image data of the image to be displayed in the display region  14   a  is the portrait (first kind image) and the terminal device  10  is held in a holding mode in which the cross button switch  16  is positioned on a right side of the housing  12 , and a case in which the orientation information (image kind information) corresponding to the image data of the image to be displayed in the display region  14   a  is the landscape (second kind image) and the terminal device  10  is held in a holding mode in which the cross button switch  16  is positioned on a user&#39;s side of the housing  12 . Accordingly, the user can operate the terminal device  10  without being conscious of the holding mode of the cross button switch  16  and hence, the operability of the terminal device  10  can be enhanced. 
     Further, in the above-mentioned embodiment, the cross button switch  16  is arranged along the long side of the display region  14   a . However, the present invention is not limited to such an arrangement. For example, as shown in  FIG. 16 , the cross button switch  66  may be arranged along a short side of the display region  64   a.    
     Third Embodiment 
     One specific embodiment of the terminal device  10  is explained hereinafter in conjunction with  FIG. 16  to  FIG. 19 . For facilitating the understanding of the invention, technical features different from the above-mentioned embodiment are explained in detail and the explanation of the same technical features is omitted. 
     The cross button switch  66  is mounted on at least one end of the housing  62  and, at the same time, is arranged along a short side of the display region  64   a  of the display part  64 . The cross button switch  66  is a button switch which is operable in the upper, lower, left and right directions, and is constituted of, as shown in  FIG. 16B , a left button switch portion  66   a , an upper button switch portion  66   b , a right button switch portion  66   c  and a lower button switch portion  66   d.    
     Further, when a left-hand operation is set and an image to be displayed is a landscape image, as shown in  FIG. 17(A) , a previous document is assigned to the left button switch portion  66   a , a next page is assigned to the upper button switch portion  66   b , a next document is assigned to the right button switch portion  66   c , and a previous page is assigned to the lower button switch portion  66   d . Further, the previous page is displayed when the user operates the cross button switch  66  in the left direction, the previous document is displayed when the user operates the cross button switch  66  in the upper direction, the next page is displayed when the user operates the cross button switch  66  in the right direction, and the next document is displayed when the user operates the cross button switch  66  in the lower direction. 
     Then, when the image to be displayed is changed to a portrait, as shown in  FIG. 17(B) , the image per se is rotated by 90 degrees. Further, a previous page is assigned to the left button switch portion  66   a , a previous document is assigned to the upper button switch portion  66   b , a next page is assigned to the right button switch portion  66   c , and a next document is assigned to the lower button switch portion  66   d . Accordingly, when the housing  62  is rotated by −90 degrees as shown in  FIG. 17(C)  for allowing a user to observe the image, the terminal device  10  assumes a holding mode in which the cross button switch  66  is positioned on a user&#39;s side of the housing  62 . Then, the previous page is displayed when the user operates the cross button switch  66  in the left direction, the previous document is displayed when the user operates the cross button switch  66  in the upper direction, the next page is displayed when the user operates the cross button switch  66  in the right direction, and the next document is displayed when the user operates the cross button switch  66  in the lower direction. 
     Further, when a right-hand operation is set and an image to be displayed is a landscape image, as shown in  FIG. 17(D) , a next document is assigned to the left button switch portion  66   a , a previous page is assigned to the upper button switch portion  66   b , a previous document is assigned to the right button switch portion  66   c , and a next page is assigned to the lower button switch portion  66   d . Further, the previous page is displayed when the user operates the cross button switch  66  in the left direction, the previous document is displayed when the user operates the cross button switch  66  in the upper direction, the next page is displayed when the user operates the cross button switch  66  in the right direction, and the next document is displayed when the user operates the cross button switch  66  in the lower direction. 
     Then, when the image to be displayed is changed to a portrait, as shown in  FIG. 17(E) , the image per se is rotated by −90 degrees. Further, a previous page is assigned to the left button switch portion  66   a , a previous document is assigned to the upper button switch portion  66   b , a next page is assigned to the right button switch portion  66   c , and a next document is assigned to the lower button switch portion  66   d . Accordingly, when the housing  62  is rotated by 90 degrees as shown in  FIG. 17(F)  for allowing a user to observe the image, the terminal device  10  assumes a holding mode in which the cross button switch  66  is positioned on a user&#39;s side of the housing  62 . Then, the previous page is displayed when the user operates the cross button switch  66  in the left direction, the previous document is displayed when the user operates the cross button switch  66  in the upper direction, the next page is displayed when the user operates the cross button switch  66  in the right direction, and the next document is displayed when the user operates the cross button switch  66  in the lower direction. 
     (Key Assignment Setting Table) 
     Further, in the above-mentioned key assignment setting table, as shown in  FIG. 18 , when the orientation information is a portrait, irrespective of whether the dominant hand setting is set as the right hand or the left hand, a previous page is assigned to the left button switch portion  66   a , a previous document is assigned to the upper button switch portion  66   b , a next page is assigned to the right button switch portion  66   c , and a next document is assigned to the lower button switch portion  66   d . Further, when the orientation information is a landscape and the dominant hand setting is set as the right hand, a next document is assigned to the left button switch portion  66   a , a previous page is assigned to the upper button switch portion  66   b , a previous document is assigned to the right button switch portion  66   c , and a next document is assigned to the lower button switch portion  66   d . When the orientation information is a landscape and the dominant hand setting is set as the left hand, a previous document is assigned to the left button switch portion  66   a , a next page is assigned to the upper button switch portion  66   b , a next document is assigned to the right button switch portion  66   c , and a previous page is assigned to the lower button switch portion  66   d.    
     Further, by referencing this raster data setting table, it is possible to recognize the raster data per se, the orientation information of the raster data or the like. The EEPROM  23  functions as an image data memory part. That is, in the EEPROM  23 , either one of the portrait image (longitudinally-elongated image data, the second kind image information) which is observed by the user in a holding mode in which the cross button switch  16  (operation part, cross operation part) is positioned on either one of left and right sides of the housing  12 , and the landscape image (laterally-elongated image data, the first kind image information) which is observed by the user in a holding mode in which the cross button switch  16  is positioned on a deep side of the housing  12  is stored as the orientation information (image kind information) corresponding to each image data. 
     (Explanation of Display Updating Processing Flow of Terminal Device  10 ) 
     A subroutine executed in step S 93  shown in  FIG. 10  is explained in conjunction with  FIG. 19 . 
     As shown in  FIG. 19 , when the CPU  20  determines that the orientation information corresponding to the current page is a portrait (step S 151 : YES) and the dominant hand setting is set as the left hand (step S 152 : NO), button switch setting is performed such that a previous page is assigned to a left button switch portion  66   a , a previous document is assigned to an upper button switch portion  66   b , a next page is assigned to the right button switch portion  66   c , and a next document is assigned to the lower button switch portion  66   d  (step S 183 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs assignment of control contents corresponding to the operation direction of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on a display region  14   a  and dominant hand setting (operation mode) which is already set. Then, the CPU  20  performs a control of keeping display of raster data on a predetermined page of a designated document (step S 184 ), and this subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a portrait (second kind image information), when the dominant hand setting is set as the left hand (left hand operation mode), the CPU  20  performs a control of displaying an image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation portion) is positioned on a left side of the housing  12 . 
     When the CPU  20  determines that the orientation information corresponding to the current page is a landscape (step S 151 : NO) and the dominant hand setting is set as the right hand (step S 153 : YES), button switch setting is performed such that a next document is assigned to the left button switch portion  66   a , a previous page is assigned to the upper button switch portion  66   b , a previous document is assigned to the right button switch portion  66   c , and a next page is assigned to the lower button switch portion  66   d  (step S 185 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs assignment of control contents corresponding to the operation direction of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Then, the CPU  20  performs a control of displaying raster data on a predetermined page of a designated document by rotating 180 degrees (step S 186 ), and this subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a landscape (first kind image information), when the dominant hand setting is set as the right hand (the right-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a right side of the housing  12 . 
     Further, when the CPU  20  determines that the orientation information corresponding to the current page is a landscape (step S 151 : NO) and the dominant hand setting is set as the left hand (step S 153 : NO), button switch setting is performed such that a previous document is assigned to the left button switch portion  66   a , a next page is assigned to the upper button switch portion  66   b , a next document is assigned to the right button switch portion  66   c , and a previous page is assigned to the lower button switch portion  66   d  (step S 187 ). The CPU  20  functions as an operation assignment control part. That is, the CPU  20  performs assignment of control contents corresponding to the operation direction of the cross button switch  16  (cross operation part) based on the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  and dominant hand setting (operation mode) which is already set. Then, the CPU  20  performs a control of keeping display of raster data on a predetermined page of a designated document (step S 188 ), and this subroutine is finished. The CPU  20  functions as a display control part. That is, in case the orientation information (image kind information) corresponding to image data of an image to be displayed on the display region  14   a  is a landscape (first kind image information), when the dominant hand setting is set as the left hand (the left-hand operation mode), the CPU  20  can perform a control of displaying the image at an angle which allows a user to observe the display region in a holding mode in which the cross button switch  16  (operation part) is positioned on a left side of the housing  12 . 
     Further, although the above-mentioned embodiments adopt the terminal device  10  which includes the cross button switch  16 , the present invention is not limited to such constitution. For example, as shown in  FIG. 20A , the terminal device  10  may include a button switch  76  which is operable in the lateral direction (or vertical direction). Further, in the above-mentioned embodiments, both of the housing  12  and the display region  14   a  of the display device  14  have a rectangular shape. However, the present invention is not limited to such a shape. For example, as shown in  FIG. 20B , in case a display region  84   a  of a display device  84  is formed in a rectangular shape, the housing  82  per se may be formed in a circular shape in place of a rectangular shape.