Abstract:
An electronic apparatus having a display function is able to alter the orientation of an image displayed on a display means for displaying images between a first orientation and a second orientation different from the first orientation. A plurality of operating means are provided at positions symmetrical between disposal positions which take the first orientation as a standard orientation and disposal positions which take the second orientation as a standard orientation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/905,956, filed Oct. 5, 2007, now issued as U.S. Pat. No. 8,102,458 on Jan. 24, 2012, which is a divisional application of abandoned U.S. patent application Ser. No. 10/169,248, filed Oct. 3, 2002. U.S. patent application Ser. No. 10/169,248 is a national stage of PCT/JP99/07392, filed Dec. 28, 1999, the entire contents of all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic apparatus having a display function, and particularly to an electronic apparatus having a display function capable of altering the orientation of images displayed on a display means. 
     2. Description of the Related Art 
     Conventional electronic apparatuses having a display function are able to display and edit input data on a display surface. 
     A plurality of buttons for instructing the movement of a cursor are provided on the outer left hand side of the display surface in this electronic apparatus having a display function, and data is input using a data input pen. 
     However, in the above electronic apparatus having a display function, the aforementioned buttons are provided on the outer left hand side of the display screen so that a right handed person may use the apparatus. Specifically, a right handed person can hold the pen in their right hand and instruct the movement of the cursor by operating the buttons with their left hand. Furthermore, in the above type of electronic apparatus having a display function, when the buttons are provided at the outer left hand side of the display surface and the pen is being held in the right hand of the user, images are displayed with an orientation which makes them easily seen by a right handed person. 
     Consequently, if the electronic apparatus having a display function is inverted in order to make it easier for a left handed person to operate the buttons with their right hand and input data using the pen in their left hand, images are also displayed upside down making them difficult to discern. Moreover, if the electronic apparatus having a display function is inverted, the positions of the plurality of buttons relative to each other are switched after the inversion from the positions before the inversion. Accordingly, the operability of the plurality of buttons is changed. 
     SUMMARY OF THE INVENTION 
     The present invention was developed in view of the above, and it is an objective thereof to provide an electronic apparatus having a display function in which the operability of a plurality of operating means can be improved. 
     In order to achieve the above aim, the first aspect of the present invention is an electronic apparatus having a display function comprising: display means for displaying an image; a plurality of operating means; and control means for controlling the display means so that an orientation of an image displayed on the display means is altered between a first orientation and a second orientation which is different from the first orientation, wherein the operating means is disposed at a position which is symmetrical between a disposal position which takes the first orientation as a standard orientation and a disposal position which takes the second orientation as a standard orientation. 
     Namely, the electronic apparatus having a display function according to the first aspect is able to switch the orientation of an image displayed on the display means between a first orientation and a second orientation which is different from the first orientation. This allows the orientation of an image to be matched with the orientation of the electronic apparatus having a display function when the orientation of the electronic apparatus having a display function is altered, thus preventing images from becoming difficult to discern. 
     The plurality of operating means of the electronic apparatus having a display function is disposed at a position symmetrical to a disposal position which takes the first orientation as the standard orientation and a disposal position which takes the second orientation as the standard orientation. Consequently, even if the orientation of the electronic apparatus having a display means is altered thereby altering the orientation of an image to the first orientation or the second orientation, the operability of the plurality of operating means can be kept the same. Thus the operability of the plurality of operating means is improved. 
     Note that the operating means may be a cursor movement instructing means for instructing the movement of a cursor displayed on a display means. In this case, the control means controls the display means so that the cursor moves in accordance with a cursor movement instruction from the cursor movement instructing means. 
     Furthermore, the operating means may also be an orientation alteration instructing means for giving an instruction for the orientation of the image to be switched between a first orientation and a second orientation. In this case, the control means controls the display means so that the orientation of an image is switched between a first orientation and a second orientation in accordance with an image orientation alteration instruction from the orientation alteration instructing means. 
     The second aspect of the present invention is an electronic apparatus having a display function comprising: display means for displaying an image; orientation alteration instructing means for giving an instruction for an orientation of an image displayed on the display means to be altered between a first orientation and a second orientation which is different from the first orientation; and control means for controlling the display means so that the orientation of the image is altered between the first orientation and the second orientation in accordance with an image orientation alteration instruction from the orientation alteration instructing means, wherein the electronic apparatus having a display function further comprises a plurality of cursor movement instructing means for instructing a movement of a cursor displayed on the display means, and wherein when a movement of the cursor is instructed by the cursor movement instructing means, the control means controls the display means so that the orientation of an image displayed at the time the instruction is given is set as standard, and the cursor moves in directions which correspond to a position at which the cursor movement instructing means is disposed. 
     In the same way as in the first aspect, in the electronic apparatus having a display function according to the second aspect of the present invention, the orientation of the image displayed on the display means is able to be switched between a first orientation and a second orientation which is different from the first orientation. Moreover, the electronic apparatus having a display function is further provided with a plurality of cursor movement instructing means for instructing the movement of the cursor displayed on the display means. In addition, when a movement of the cursor is instructed by the cursor movement instructing means, the control means controls the display means so that the orientation of the image displayed at the time the instruction is given is set as standard, and the cursor moves in directions which correspond to the position at which the cursor movement instructing means is disposed. Because the orientation of the image displayed at the time the instruction was given by the cursor movement instructing means has been set as the standard orientation and the cursor moves in directions which accord with this orientation, the cursor movement instructing means may be operated in accordance with the orientation of the image. Moreover, even if the orientation of the image is altered, the operability of the cursor movement instructing means can be kept the same and the operability of the plurality of cursor movement instructing means can be improved. 
     The third aspect of the present invention is an electronic apparatus having a display function comprising: display means for displaying an image; orientation alteration instructing means for giving an instruction that an orientation of an image displayed on the display means be altered between a first orientation and a second orientation which is different from the first orientation; and control means for controlling the display means so that the orientation of the image is altered between the first orientation and the second orientation in accordance with an image orientation alteration instruction from the orientation alteration instructing means, wherein the electronic display apparatus having a display function further comprises a plurality of cursor movement instructing means including a first cursor movement instructing means and a second cursor movement instructing means for instructing a movement of a cursor displayed on the display means, and wherein when a movement of the cursor is instructed by the first cursor movement instructing means, the control means controls the display means so that the cursor is moved in a first direction when the image has the first orientation and in a second direction different from the first direction when the image has the second orientation, and when a movement of the cursor is instructed by the second cursor movement instructing means, the control means controls the display means so that the cursor is moved in the second direction when the image has the first orientation and in the first direction when the image has the second orientation. 
     In the same way as in the first and second aspects of the present invention, in the electronic apparatus having a display function according to the third aspect of the present invention, the orientation of the image displayed on the display means can be switched between a first orientation and a second orientation which is different from the first orientation. Furthermore, the electronic apparatus having a display function is further provided with a plurality of cursor movement instructing means including a first cursor movement instructing means and a second cursor movement instructing means for instructing the movement of a cursor displayed on the display means. In addition, when an instruction to move the cursor is given by the first cursor movement instructing means, the control means controls the display means so that the cursor is moved in a first direction when the image has the first orientation and in a second direction which is different from the first direction when the image has the second orientation, and when a movement of the cursor is instructed by the second cursor movement instructing means, the control means controls the display means so that the cursor is moved in the second direction when the image has the first orientation and in the first direction when the image has the second orientation. In this way, because the direction in which the cursor moves when instructed by the first cursor movement instructing means and the direction in which the cursor moves when instructed by the second cursor movement instructing means are the reverse of each other both when the image has the first orientation and when the image has the second orientation, the first cursor movement instructing means and the second cursor movement instructing means may be selectively operated in accordance with the orientation of the image. Consequently, even if the orientation of the image is altered, the operability of the cursor movement instructing means can be kept the same and the operability of the plurality of cursor movement instructing means by a left handed person can be improved. Note that, in this case, the first direction and the second direction may be set so as to be the reverse of each other. 
     Note also that in the above first through third embodiments, the first orientation and the second orientation may be set so as to be opposite to each other. 
     The fourth aspect of the present invention is an electronic apparatus having a display function comprising: display means for displaying an image; orientation alteration instructing means for giving an instruction that an orientation of an image displayed on the display means be altered; a plurality of cursor movement instructing means for instructing a movement of a cursor displayed on the display means; and control means for controlling the display means in such a way that the orientation of the image is altered when an instruction to alter the orientation of the image is given by the orientation alteration instructing means and for controlling the display means in such a way that the cursor is moved when an instruction to move the cursor is given by the cursor movement instructing means, wherein the control means controls a movement direction in which the cursor is moved when an instruction to move the cursor is given by the cursor movement instructing means so that the movement direction is a direction determined in advance to correspond to the relative positions at which each of the plurality of movement instructing means are disposed, regardless of the orientation of the image which has been altered in accordance with the instruction from the orientation alteration instructing means. 
     Namely, in the electronic apparatus having a display function according the fourth aspect of the present invention, the orientation of an image is altered in accordance with an instruction to alter the orientation of the image, and the cursor is moved in accordance with an instruction to move the cursor. In addition, the control means controls the movement directions in which the cursor is moved when instructions to move the cursor are given by the cursor movement instructing means so that the movement directions are directions determined in advance to correspond to the positions relative to each other at which each of the plurality of movement instructing means are disposed, regardless of the orientation of the image which has been altered in accordance with an instruction from the orientation alteration instructing means. In this way, because the directions in which the cursor is moved are set so as to be directions determined in advance to correspond to the relative positions at which each of the plurality of movement instructing means are disposed regardless of the orientation of the image, even if the orientation of the image is altered, the operability of the cursor movement instructing means can be kept the same and the operability of the plurality of cursor movement instructing means can be improved. 
     The first through fourth aspects of the present invention may also be structured according to the following descriptions. 
     Namely, the orientation alteration instructing means comprises a tilt direction detecting sensor for detecting a direction of a tilt of a body of an electronic apparatus having a display function, and the control means controls the display means so that an orientation of the image matches a direction set in advance relative to the tilt direction detected by the tilt direction detecting sensor. 
     Moreover, the electronic apparatus having a display function is structured so that photographing means for photographing an object can be mounted in a plurality of directions relative to the body of the electronic apparatus having a display function, and the control means controls the display means so that an image obtained by photography using the photographing means is displayed and an orientation of the image matches a direction determined in advance relative to a direction in which the photographing means is mounted. Note that, in this case, the electronic apparatus having a display function may be structured so that the photographing means may be mounted at a single location or at least at any one location in each of a plurality of directions relative to the body of the electronic apparatus having a display function. 
     Moreover, the control means controls the display means so that, when a process execution instruction image for giving an instruction to execute a predetermined process is displayed at the same time as an instruction is given by the orientation alteration instructing means to alter the orientation of an image, the orientation of the image including the process execution instruction image is altered by the display means. 
     Moreover, the electronic apparatus having a display function is a portable electronic apparatus. 
     Furthermore, the orientation alteration instructing means is a menu item displayed on the display means. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a portable display apparatus according to the first embodiment of the present invention. 
         FIG. 2  is a block diagram showing a control system of the portable display apparatus according to the present embodiment. 
         FIG. 3  is a flow chart showing a screen inversion process routine. 
         FIGS. 4A to 4C  show results of a screen determining process. 
         FIGS. 5A and 5B  show states where the apparatus body and screen have been inverted. 
         FIG. 6  is a flow chart showing a cursor movement process routine. 
         FIGS. 7A and 7B  show results of a cursor movement process. 
         FIG. 8  is a perspective view showing an apparatus in a state where a camera unit has been mounted thereon. 
         FIG. 9  is a flow chart showing a screen direction adjustment process routine when a camera unit is mounted on the apparatus. 
         FIG. 10  shows a result of a screen direction adjustment process. 
         FIG. 11  shows another result of a screen direction adjustment process. 
         FIG. 12  shows another example (the display apparatus is not shown) of a camera unit mounted on an apparatus body. 
         FIG. 13  is a block diagram of a portable display apparatus according to a variant example. 
         FIG. 14  is a flow chart showing a routine for a screen direction adjustment process which starts when the software for each application is started. 
         FIG. 15  is a flow chart showing a routine for an enlarged display process according to the variant example. 
         FIG. 16  shows the displayed screen for enlarged display mode setting. 
         FIGS. 17A and 17B  show the contents of an enlarged display of a split image. 
         FIG. 18  is a flow chart showing a split image movement process routine. 
         FIGS. 19A to 19C  are views explaining the fine adjustment of the movement of a split image. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of the present invention will now be explained in detail with reference to the drawings. A portable display apparatus (PDA) according to an electronic apparatus having a display function of the present embodiment is shown in  FIG. 1 . As is shown in  FIG. 1 , the portable display apparatus is provided with a display device  12  comprising a liquid crystal display or the like for displaying images. The portable display apparatus is further provided with a first screen inversion instruction button  14  for giving an instruction for the screen of the display device  12  to be inverted (described below) and a second screen inversion instruction button  16 . The portable display apparatus is further provided with movement instruction buttons  18 ,  20 ,  22 , and  24  for giving instructions for the cursor displayed on the display device  12  to be moved (described below). Note that the first screen inversion instruction button  14 , the second screen inversion instruction button  16 , and the movement instruction buttons  18 ,  20 ,  22 , and  24  are all disposed at symmetrical positions relative to each of the orientations to which an image can be altered. Note also that one side of the body of the portable display apparatus houses a touch pen  13  for inputting data by touching the screen of the display device  12 . Note further that a touch sensor  11 , as shown in  FIG. 2 , for detecting the position on the screen of the display device  12  touched by the touch pen  13  is provided at the screen of the display device  12 . 
     Next, the control system of the portable display apparatus according to the present embodiment will be described. As is shown in  FIG. 2 , this control system is provided with a microcomputer  24 . The microcomputer  24  is provided with a CPU  26 , ROM  28 , RAM  30 , and an input/output (I/O) port  32 . These are all structured so as to be connectable to each other via a bus  34 . The display device  12  (described below), the first screen inversion instruction button  14 , the second screen inversion instruction button  16 , the movement instruction buttons  18  to  24 , and the touch sensor  11  are connected to the input/output port  32 . 
     The screen inversion process routine which starts when either the first screen inversion instruction button  14  or the second inversion instruction button  16  is activated is shown in  FIG. 3 . In step  102  of  FIG. 3 , a determination is made as to whether or not the activation of the first screen inversion instruction button  14  or the second screen inversion instruction button  16  which allows the screen inversion process routine to start has been terminated. If the activation has been terminated, then, in step  104 , a determination is made as to whether or not the activation time T, which is the time the screen inversion instruction button has been operated in an activated state (the time from when the present routine started until the time the determination in step  102  is affirmative), is longer than a predetermined time t (e.g. 1 second). 
     Note that in the present embodiment, as is shown in  FIG. 4A , a plurality of icons  111  and menus  112 , for example, are displayed on the screen  110  of the display device  12  and the cursor is displayed on one of the menu bars from one of the icons  111  and menus  112 . A selection can then be made as to whether to instruct the screen to be inverted or whether to instruct normal processing in accordance with the length of time the screen inversion instruction button  14  or  16  is activated. 
     Namely, if the activation time T is determined in step  104  to be greater than the time t, then, in step  106 , the screen is inverted. Namely, the screen  110  shown in  FIG. 4A  is inverted, as is shown in  FIG. 4B . The menu  112  is also inverted at this time. If, however, the activation time T is not determined in step  104  to be greater than the time t, then, in step  108 , normal processing is performed. Namely, as is shown in  FIG. 4A , if the cursor is displayed on an icon representing schedule application software, then, as is shown in  FIG. 4C , the schedule application software, which includes a menu  114 , is run. Note that the orientation of the screen shown in  FIG. 4C  is the same as the orientation of the screen shown in  FIG. 4A , while the orientation of the screen shown in  FIG. 4B  is the reverse of the orientation of the screen shown in  FIG. 4A . 
     If the orientation of the screen can be altered in this way, then the following effect can be obtained. Namely, a right handed person holds the touch pen in their right hand and inputs data using the pen while operating the buttons with their left hand in order to move the cursor (data input mode). Therefore, the orientation of the screen when looking at the screen is desirably such that the various buttons are positioned at the left hand side, as seen in  FIG. 5A  (refer to the arrows indicating up and down in  FIG. 5A ). However, if the orientation of the screen when looking at the screen is such that the various buttons are positioned at the right hand side, as seen in  FIG. 5B  (refer to the arrows indicating up and down in  FIG. 5B ), then operations in which data has to be input with the right hand using the touch pen while the buttons are operated also with the right hand are extremely cumbersome. In this case, if the orientation of the portable display apparatus as seen from the screen side is altered so that the various buttons are positioned at the left hand side, then the screen ends up being inverted (the reverse of the orientation shown in  FIG. 5A ). Therefore, by inverting the screen by activating a screen inversion instruction button for a predetermined time or longer in the state shown in  FIG. 5B , the orientation of the screen can be altered to that shown in  FIG. 5A . The above also applies in the case of a left handed person. Namely, a left handed person holds the touch pen in their left hand and inputs data using the pen while operating the buttons to move the cursor with their right hand (data input mode). Therefore, the orientation of the screen when looked at from the screen side is desirably such that the various buttons are positioned at the right hand side, as seen in  FIG. 5B  (refer to the arrows indicating up and down in  FIG. 5A ). Therefore, as explained above, in the present embodiment, because the orientation of the screen can be altered independently of the apparatus body, the screen can be adjusted to an orientation which meets the needs of both a left handed person and a right handed person, thus improving the operability of the apparatus. 
     Moreover, because the orientation of the screen can be adjusted independently of the apparatus body, when the orientation of the screen is altered in this way, if the directions of movement of the cursor are also altered relatively together with the alteration of the screen orientation, operating the cursor buttons is difficult. Namely, when the orientation of the screen when looking at the screen is such that the various buttons are positioned at the left hand side, as shown in  FIG. 7A , then the cursor  120 , which is positioned at icon A, moves to the icon D, the icon E, the icon C, and the icon B when the movement instructing buttons  18 ,  20 ,  22 , and  22  respectively are activated. When the screen is inverted, as is shown in  FIG. 7B , if the cursor  120 , which is positioned at icon A, moves to the icon D, the icon E, the icon C, and the icon B when the movement instructing buttons  18 ,  20 ,  22 , and  22  respectively are activated, then the direction in which the user presumes the cursor will move when the movement instructing buttons are operated is the direct opposite to the direction in which the cursor actually does move, causing a feeling of confusion in the user. 
     Therefore, in the present embodiment, regardless of the orientation of the screen, absolute directions which use the orientation of the body of the portable display apparatus as a reference are designated as the directions in which the cursor is moved by each of the movement instructing buttons. 
     Namely, a cursor movement process routine which starts when one of the movement instructing buttons  18  to  24  is activated is shown in  FIG. 6 . In step  116  of  FIG. 6 , the activated movement instructing button is detected. In step  118 , the cursor is moved in a predetermined direction (an absolute direction which uses the orientation of the body of the portable display apparatus as a reference) which corresponds to the detected movement instructing button. 
     For example, when the orientation of the screen when looking at the screen is such that the various buttons are positioned at the left hand side of the apparatus body, as shown in  FIG. 7A , if the movement instructing buttons  18 ,  20 ,  22 , and  24  are activated, the cursor, which was positioned over the icon A, moves respectively over the icons D, E, C, and B. While in this state, if the screen is then inverted, as is shown in  FIG. 7B , if the movement instructing buttons  18 ,  20 ,  22 , and  24  are activated, the cursor, which was positioned over the icon A, moves respectively over the icons B, C, E, and D. 
     Furthermore, the present embodiment may be structured such that a camera unit  122  housing a camera  124  for photographing objects which can be rotated by adjusting a knob  126  may be mounted in a plurality of directions relative to the body of the portable display apparatus, as shown in  FIG. 8 . Namely, in this variant example, as shown in  FIGS. 10 and 11 , a screw  140  is provided inside the camera unit  122 . Screw holes are formed in both one edge and another edge of the portable display apparatus to receive the screw  140 . The camera unit  122  is thus formed so as to be mountable on either one edge or the other edge of the portable display apparatus body. Note that, when a camera unit  124  is mounted on the portable display apparatus body, the camera control system is connected to the portable display apparatus control system via an unillustrated terminal. 
     As is shown in  FIG. 10 , when the camera unit  122  is mounted so that the various buttons may be operated using the right hand of the user, it is desirable that the orientation of the screen is such that the top of the screen is closest to the edge on which the camera unit  122  is mounted (view mode). Moreover, as is shown in  FIG. 11 , when the camera unit  122  is mounted so that the various buttons may be operated using the left hand of the user, it is again desirable that the orientation of the screen is such that the top of the screen is closest to the edge on which the camera unit  122  is mounted (view mode). In this way, if the camera unit  122  is formed so as to be mountable in various directions relative to the body of the portable display apparatus, then if the orientation of an image is fixed relative to the apparatus body regardless of the direction in which the camera is mounted, screen viewability is poor. 
     Therefore, in the present embodiment, when the camera unit  122  is mounted, the orientation of the screen can be made to match directions determined in advance for each of the directions in which the camera unit  122  can be mounted. Namely, the screen direction adjustment process shown in  FIG. 9  is started when a camera unit  122  is mounted. In step  132 , the direction in which the camera unit  122  is mounted relative to the apparatus body is detected. Namely, in the present embodiment, a detection is made as to whether the camera unit  122  is mounted so that the various buttons can be operated with the right hand of the user, as shown in  FIG. 10 , or whether the camera unit  122  is mounted so that the various buttons can be operated with the left hand of the user, as shown in  FIG. 11 . 
     In step  134 , the direction of the screen is adjusted to an orientation which corresponds to the direction in which the camera unit  122  has been mounted. Namely, if a determination is made that the camera unit  122  has been mounted in the state shown in  FIG. 10 , the orientation of the screen is set such that the top of the screen is closest to the edge on which the camera unit  122  is mounted. If a determination is made that the camera unit  122  has been mounted in the state shown in  FIG. 11 , the orientation of the screen is set such that the top of the screen is closest to the edge on which the camera unit  122  is mounted. 
     In the example described above, the camera unit  122 , depicted in  FIG. 12 , was formed so as to be mountable at two locations on the apparatus body, however, the present invention is not limited to this and the camera unit  122  may be made mountable to the rear surface of the portable display apparatus by a screw  142  provided at a position on the camera unit  122  which corresponds to the rear surface of the portable display apparatus. 
     Note that it is rare for the portable display apparatus to be operated when the body thereof is horizontal and instead it is usually operated when the body is tilted. In this case, the orientation of the apparatus body when a right handed person is operating the portable display apparatus is the opposite to that when a left handed person is operating the portable display apparatus. Consequently, detecting the direction of the tilt of the portable display apparatus can provide the knowledge as to which direction the screen should be oriented. 
     Therefore, it is also possible to control the orientation of the screen in accordance with the direction of the tilt of the portable display apparatus. In this case, as is shown in  FIG. 13 , a tilt sensor  150  is provided for detecting the direction of the tilt of the portable display apparatus and the screen direction adjustment process routine shown in  FIG. 14  is executed. This routine is started when the software for each application is run. Namely, in step  152 , the direction of the tilt of the portable display apparatus is detected. In step  154 , the direction of the screen is adjusted to an orientation which corresponds to the tilt direction. Namely, when the data input mode application software is run, when the tilt is such that the various buttons are positioned on the left hand side of the screen, the orientation of the screen is adjusted to one for when the buttons are positioned to the left of the screen. In contrast, when the tilt is such that the various buttons are positioned on the right hand side of the screen, the orientation of the screen is adjusted to one for when the buttons are positioned to the right of the screen. If the view mode application software is run, when the tilt is such that the various buttons are positioned on the right hand side of the screen, the orientation of the screen is adjusted to one for when the buttons are positioned to the right of the screen. In contrast, when the tilt is such that the various buttons are positioned on the left hand side of the screen, the orientation of the screen is adjusted to one for when the buttons are positioned to the left of the screen. 
     In the example described above, the screen inversion is carried out on the basis of the operation of the screen inversion instruction buttons, the result of the detection by the tilt sensor, and the direction in which the camera unit is mounted, however, the present invention is not limited to this. For example, a menu bar for inverting the screen may be displayed on the screen and an instruction to invert the screen may be given by touching the menu bar with a touch pen. 
     Furthermore, in the above described embodiment, the orientation of the screen was altered by 180 degrees, however, the present invention is not limited to this, and the screen may be altered by another angle, for example, 90 degrees. In this case, the screen may be inverted in sequence by 90 degrees each time the screen inversion instruction button is activated for a predetermined length of time or more. 
     Furthermore, the following processings may also be performed in the present portable display apparatus. 
     An enlarged display processing routine which starts when either of the above first screen inversion instruction button  14  and second screen inversion instruction button  16  is activated is shown in  FIG. 15 . In step  42  of  FIG. 15 , a determination is made as to whether or not enlarged display mode is set for the application software being executed to display the current image on the display device  12 . An enlarged display mode setting screen  64  for setting an enlarged display mode for each application software is shown in  FIG. 16 . This enlarged display setting screen is displayed when an environment setting button  62  set in an unillustrated initial screen is activated. As is shown in  FIG. 16 , an area  68  for making a setting in the menus  66  of each application software such that that particular application software is only displayed in standard mode, and an area  70  for making a setting so as to make it possible for a partial image which is described below to be displayed in enlarged display mode at a predetermined magnification (400% in the present embodiment) are correspondingly provided on the enlarged display mode setting screen  64 . By selecting the area  68  or  70  selectively for each application, the user can make a setting so that the application is only displayed in standard mode or so that the application can be displayed in enlarged display mode. In the present embodiment, an example is described in which the software of a scheduling application is set so as to be displayable in enlarged display mode. 
     In the next step  44 , a variable C is increased by an increment of one. The variable C is separately determined for each application and is reset each time the software of an application is executed (C=0). Each time the variable C is incremented by one, a partial image, formed by splitting the image displayed on the display device  12  into a predetermined number of portions (four in the present embodiment), is identified as being, in sequence, a top left partial image  74 , a top right partial image  76 , a bottom left partial image  78 , and a bottom right partial image  80 , as is shown in  FIG. 17A . 
     In step  46 , a determination is made as to whether or not the variable C is equal to or less than the sum C 0  (four in the present embodiment) of the partial images. If the variable C≦C 0 , the partial image identified by the variable C in step  48  is displayed in enlarged display mode. Namely, in step  48 , the partial image identified by the variable C (for example, the top left partial image  74  when C=1) is displayed at the aforementioned enlarged magnification (400%), as is shown in  FIG. 17B . 
     If, however, the determination in step  46  is that C&gt;C 0 , after each of the partial images have been displayed in enlarged display mode, because one of the screen inversion buttons  14  and  16  is activated, the display is set to standard mode in step  50  and, in step  52 , the variable is reset to 0. 
     As has been explained above, because the user merely has to activate one of the screen inversion buttons  14  and  16  when altering a partial image, the alteration of a partial image can be easily performed. 
     A partial image movement processing routine executed when one of the movement instruction buttons  18  to  24  is activated is shown in  FIG. 18 . In step  82  of  FIG. 18 , a determination is made as to whether or not an image is being displayed in enlarged display mode on the display device  12 . If the result of the determination is that the image is being displayed in enlarged display mode, then, in step  84 , whether or not one of the movement instruction buttons  18  to  24  has been activated is detected. In the next step  86 , the partial image is moved by a predetermined number of dots D 0  in a direction determined in advance corresponding to the detected movement instruction button  18  to  24 . 
     Namely, in the present embodiment, the movement instruction button  18  is determined in advance to instruct the partial image to be moved upwards; the movement instruction button  20  is determined in advance to instruct the partial image to be moved towards the right; the movement instruction button  22  is determined in advance to instruct the partial image to be moved towards the left; and the movement instruction button  24  is determined in advance to instruct the partial image to be moved downwards. Furthermore, in the present embodiment, the partial image is set in advance to be moved by a predetermined number of dots D 0  (for example, 12 dots) when one of the movement instruction buttons  18  to  24  is activated, as is shown in  FIG. 19A . As a result, in the above described example, namely, when the movement instruction button  20  is activated to instruct a movement to the right while the top left partial image  74  is being displayed in enlarged display mode, the partial image is altered to a partial image whose left and right sides are moved further to the right by the predetermined number of dots D 0 . Accordingly, compared to the top left partial image  74  displayed in enlargement before the movement instruction button  20  is activated, as shown in  FIG. 19B , the partial image displayed in enlargement when the movement instruction button  20  has been activated is moved towards the right by the predetermined number of dots D 0 , as shown in  FIG. 19C . 
     In the above described embodiment, the partial image is moved by a predetermined number of dots each time one of the movement instruction buttons  18  to  24  is activated, however, the present invention is not limited to this. For example, the speed of movement of the partial image may be controlled so as to increase the longer the movement instruction button is activated. Moreover, in the above described embodiment, the movement of the position of the partial image is instructed by a movement instruction button, however, the present invention is not limited to this. For example, if a touch pen is used, then the movement of the partial image may be instructed by touching the display screen of the display device  12  with the touch pen. In this case, the partial image may be moved in a direction towards the position on the screen touched by the touch pen from the center of the display screen of the display device  12 . Furthermore, the speed of movement of the partial image may be controlled so as to increase the further the distance from the center of the display screen of the display device  12  to the position touched by the touch pen. 
     Note that, in the above describe embodiment, display enlargement was instructed using the screen inversion buttons and movement of the partial image was instructed using the movement instruction buttons, however, the present invention is not limited to this. For example, these instructions may be given using a menu bar provided on the display screen. Namely, the above instructions may be given by touching the menu bar with the touch pen. 
     Moreover, in the present embodiment, an image was split into four portions, however, the present invention is not limited to this. For example, the image may be split into a plurality of portions other than four. It is also possible to set the number of portions into which an image is split depending on the aforementioned application software. 
     Further, in the present embodiment, the magnification of the enlargement when a partial image was displayed in enlargement was fixed to correspond to the software of each application, however, the present invention is not limited to this. For example, it is possible to optionally set the magnification of the enlargement when a partial image is displayed in enlargement for each application. 
     Note also that, in the above example, the reason why the image was split into four and the enlargement magnification was set to 400% was in order to correspond the area of the enlarged partial image to the area for displaying an image on the display device  12 . Accordingly, the enlargement magnification when an image is split into a plurality of portions other than four is a magnification at which the area of the enlarged partial image corresponds to the area for displaying an image on the display device  12 . Note that, in the present invention, the above described enlargement magnification is not necessarily a magnification at which the area of the enlarged partial image corresponds to the area for displaying an image on the display device  12 , and it is sufficient if the enlargement magnification is such that the area of the enlarged partial image is at least equal to or less than the area for displaying an image on the display device  12 . Note further that, in this case, it is possible to display the enlarged partial image by superposing the enlarged partial image over the image before enlarging the image. 
     In the above described embodiments, a portable display apparatus was used in the examples described, however, the present invention is not limited to this. The present invention may also be applied to other electronic devices such as, for example, a personal computer and a digital camera.