Patent Publication Number: US-6342894-B1

Title: Icon display method

Description:
This application is a continuation of application Ser. No. 07/855,087, filed Mar. 20, 1992 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to icon display for a data processing apparatus, and more particularly, to an icon display method which has an improved operability and workability. 
     2. Description of the Related Art 
     In recent years, user interfaces for personal computers or work stations have been proposed, which assure easy handling of computers and user friendly operation by displaying a plurality of icons on a display screen. Sometimes, the meaning of an icon may not be self-evident from its form. Therefore, a supplementary explanation of the meanings of the icons is given by a help function or the like in some computer systems. In other systems, to make the displayed icon&#39;s contents clear, a display area for the single icon is enlarged so that the icon can be displayed in a larger icon font in the enlarged icon display area. 
     However, where the display area for the single icon is enlarged, although the icon can be discriminated at a glance, the number of icons displayed on the screen is decreased. Furthermore, where the display area for the single icon is reduced so that many icons can be displayed on one screen, it may be difficult for the operator to know the functions of the icons at a glance. Therefore, the operator interrupts the operation to refer to an attached pamphlet, such as a quick reference guide, for explanation of icons. Consequently, operability deteriorates. 
     Where it is impossible to know the functions of the icons because they are displayed in the small display areas, explanation may be offered by other methods, such as the help function. However, in that case, the operator must interrupt the operation to display of the help guidance screen and must learn the operation of displaying the help guidance screen. Consequently, operability deteriorates. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned drawbacks of the conventional icon display method, an object of the present invention is to provide an icon display method in which a single object is explained using a plurality of icons rather than a single icon. 
     To achieve the above object, the present invention provides an icon display method for a data processing apparatus having an icon display function, which comprises registration means for registering a plurality of icons for a single object, display means for displaying the icons registered by the registration means, and instruction means for instructing display of an immediately subsequently registered icon relative to the icon displayed by the display means. 
     Another object of the present invention is to provide an icon display method which enables a plurality of icons registered for a single object to be displayed at predetermined time intervals. 
     To achieve the above object, the present invention provides an icon display method for data processing apparatus having an icon display function, which comprises registration means for registering a plurality of icons for a single object, display means for displaying the icons registered by the registration means, instruction means for instructing display of all the registered icons relative to the icon displayed by the display means, and counting means for counting the time intervals during which the icons instructed by the instruction means are displayed. All the registered icons are displayed at predetermined time intervals counted by the counting means. 
     Another object of the present invention is to provide an icon display method in which a single object is expressed by a plurality of icons, the presently displayed icon and the subsequently displayed icon having a relation similar to the two sides of a card so that display of the icons is switched over by turning over the presently displayed icon. 
     To achieve the above object, the present invention provides an icon display method for a data processing apparatus having an icon display function, which comprises registration means for registering a plurality of icons for a single object, display means for displaying the icons registered by the registration means, instruction means for instructing display of an immediately subsequently registered icon relative to the icon displayed by the display means, and control means for controlling display of the subsequent icon which is instructed by the instruction means. The presently displayed icon and the subsequently displayed icon have a relation similar to the two sides of a card, and the presently displayed icon is turned over to display the subsequent icon. 
     It is further object of the present invention to provide a display control method in which a plurality of icon fonts can be registered for a single object or function and in which the object or function can be explained using the plurality of icon patterns by switching between displays of the icons representing the object or function, and a display control apparatus therefor. 
     To achieve the further object, the present invention provides a display control apparatus in which a plurality of icons are displayed on a display screen and in which various types of functions can be executed by designating the corresponding icons. The display control apparatus includes a registration unit for registering a plurality of icon patterns for a single function, a store for storing the plurality of icon patterns registered by the registration unit according to the function, and a switch-over unit that switches over the presently displayed icon pattern to another icon pattern stored in the store. 
     With respect to the further object, the present invention also provides a display control method in which a plurality of icons are displayed on a display screen and in which various types of functions can be executed by designating the corresponding icons. The method includes registering a plurality of icon patterns for a single function, storing the plurality of registered icon patterns according to the function, and switching over display of the present icon pattern to that of a subsequent icon pattern when an instruction to switch over the presently displayed icon pattern to another icon pattern is given. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a personal computer showing an embodiment of the present invention; 
     FIG. 2 shows a hardware structure of the personal computer shown in FIG. 1; 
     FIG. 3 illustrates the structure of one unit in an icon display data table; 
     FIG. 4 illustrates the structure of one unit in a screen control data table; 
     FIG. 5 is a transition diagram showing the control operations of registering a plurality of icon fonts; 
     FIG. 6 is a transition diagram showing the control operations of displaying a subsequent icon font; 
     FIG. 7 illustrates an icon font registration parameter; 
     FIG. 8 is a flowchart showing the process of registering a plurality of icon fonts; 
     FIG. 9 is a flowchart showing the process of erasing a plurality of icon fonts; 
     FIG. 10 is a flowchart showing the process of displaying a subsequent icon font; 
     FIG. 11 illustrates another hardware structure of the personal computer shown in FIG. 1; 
     FIG. 12 is a view explaining the selection process carried out in still another embodiment of the present invention; 
     FIG. 13 illustrates control data used in the selection process; 
     FIG. 14 illustrates the starting addresses of an icon creating area; 
     FIG. 15 is a block diagram of a display control device, showing still another embodiment of the present invention; 
     FIG. 16 is a block diagram of a control unit of the display control device of FIG. 15; 
     FIG. 17 illustrates the format of icon data in an icon display data unit which manages a single object; 
     FIG. 18 illustrates the format of screen control data in a screen control data unit which manages a single object; 
     FIG. 19 is a transition diagram of the control operations when a plurality of icon fonts are registered; 
     FIG. 20 is a transition diagram of the control operations of displaying a subsequent icon font; 
     FIG. 21 illustrates the format of a memory in which the plurality of icon fonts are registered; 
     FIG. 22 is a flowchart showing the process of registering icon fonts; 
     FIG. 23 is a flowchart showing the process of erasing the icon fonts; 
     FIG. 24 is a flowchart showing the process of displaying a subsequent icon font; and 
     FIG. 25 is a flowchart showing the process of switching over an icon font display by scrolling when a subsequent icon font is displayed. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described below in detail with reference to the accompanying drawings. 
     FIG. 1 is a block diagram, illustrating the functions which are carried out on a data processing apparatus (a personal computer). In FIG. 1, a mouse (MS)  11  is a pointing device. A mouse control unit (MCONT)  12  controls the mouse  11  in terms of hardware. A mouse display control unit (MLCONT)  13  displays the operation of the mouse  11  on a screen. A display (DSP)  14  is a CRT in this embodiment. A display control unit (DCNT)  15  performs display control in terms of hardware. A screen display control unit (SCNT)  16  logically receives data whose display is requested and converts the received data into physical data. An icon display control unit (ICNT)  17  controls icon display, e.g., displays a subsequent icon among a plurality of registered icons or registers or deletes icons. An application program (APROG)  18  performs screen display requests, icon font registration and so on. 
     An icon display data table (IFNTBL)  19  stores font data for icon display and control data therefor. In this embodiment, 10 fonts are registered for each of 50 types of icons in the table  19 . The table  19  is managed by the icon display control unit  17 . A screen control data table (SCONTBL)  20  stores icon display control data including the screen display state. In this embodiment, data required to control display of 50 types of objects is registered in the table  20 . The table  20  is managed by the screen display control unit  16 . 
     FIG. 2 is a view illustrating the hardware of the block diagram of FIG.  1 . FIG. 2 shows a personal computer. In FIG. 2, a microprocessor (CPU) controls the entire personal computer according to the control procedures (programs) shown in FIGS. 8 through 10, which will be described later, and control data. A main memory (MM)  22  stores the mouse display control unit  13 , the screen display control unit  16 , the icon display control unit  17 , the application program  18 , the icon display data table  19 , the screen control data table  20 , the control procedures program and so on. A CPU bus  23  consists of an address bus, a data bus and control lines. 
     FIG. 3 shows one unit of the icon display data table  19 , that is, the icon display data format for one type of object. In FIG. 3, IFNTREC, the general term of the area in which one unit data is stored, consists of an area  31  for indicating the presently displayed icon number (CDNO), an area  32  in which a number of fonts (ITNO) currently registered for one type of object is stored, and an area  33  in which registered fonts (IFNTREG) are stored. Both the area  31  and the area  32  have 2 bytes, while the registered font area  33  has 5120 bytes which ensures that a maximum of 10 icon fonts, each having 512 bytes, can be registered. 
     FIG. 4 shows one unit of the screen control data table  20 , that is, the screen control data format for one type of object. SCONREC, the general term of the area in which one unit of data is stored, consists of an area  41  in which data (IOBJNO) identifying an object is stored, and areas  42  and  43  in which the left upper position (ILADR) and the right lower position (IRADR) of an icon, required when the icon is displayed by the display  14 , are respectively stored. The area  41  has 2 bytes, while both areas  42  and  43  have 4 bytes to allow the addresses on X and Y axes, each having two bytes, to be stored. 
     Registration, display and deletion of icons will be described below with reference to the related figures. 
     FIG. 5 is a control transition diagram illustrating the flow of control operations of registering and displaying a plurality of icon fonts for one object. 
     1) An icon font registration parameter (IFNTPRM), which will be described in detail later, is handed from the application program (APROG) to the icon display control unit (ICNT). 
     2) The icon display control unit (ICNT) processes the icon font registration parameter (IFNTPRM) and stores the processed data in the icon display data table (IFNTBL). The icon display control unit (ICNT) informs the application program (APROG) of the stored position as the object identifier (OBJNO). 
     3) The application program (APROG) transfers the left upper address of the icon font on the display (DSP) and the object identifier (OBJNO) to the screen display control unit (SCNT), and thereby requests an initial icon display of the registered object. 
     4) The screen display control unit (SCNT) stores the object identifier (OBJNO) and the display address in the screen control data table (SCONTBL), and then transfers the object identifier (OBJNO) to the icon display control unit (ICNT) and thereby requests the icon font address of the object. 
     5) The icon display control unit (ICNT) detects the font address corresponding to the object identifier (OBJNO) from the icon display data table (IFNTBL), and lets the screen display control unit (SCNT) know the detected font address. 
     6) The screen display control unit (SCNT) writes the icon font at the display address in the display control unit (DCNT) corresponding to the display address on the display (DSP), by which the icon is displayed on the display (DSP). 
     Prior to description of switching over of icon display which is achieved by the operation of a mouse, various operations of the mouse button and the corresponding functions will be described first. In this embodiment, a two-button mouse is used for the following operations. 
     1. One click of the left button: positive instruction 
     2. Two clicks of the left button: execution of the object 
     3. One click of the right button: negative instruction 
     4. Two clicks of the right button: display of a subsequent font of the icon 
     The operations of Items 1, 2 and 3, which are respectively processed by the mouse control unit (MCNT), the mouse display control unit (MLCNT) and the screen display control unit (SCNT) in this embodiment, have no direct relation to the present invention and a description of their operation is omitted. 
     The flow of control operations when the right button is clicked twice will be described below with reference to FIG.  6 . 
     1) When the operator (user) operates the mouse (MS), the mouse display control unit (MLCNT) detects the contents of that operation through the mouse control unit (MCNT). If the contents of the operation are to move the mouse, the mouse display control unit (MLCNT) writes the data on the movement of the mouse in the display control unit (DCNT) to sequentially display the icon representing the mouse on the display (DSP) according to the movement. 
     2) If the data from the mouse control unit (MCNT) indicates the button operation, the mouse display control unit (MLCNT) notifies both the physical address (X and Y coordinate values) of the mouse on the display (DSP) and the contents of the button operation (right/left button and one/two clicks) to the screen display control unit (SCNT). 
     3) The screen display control unit (SCNT) executes the process corresponding to the contents of the button operation. For example, if the right button is clicked twice, the screen display control unit, knowing that it indicates the request for display of a subsequent icon font, detects the SCONREC having the ILADR and IRADR corresponding to the X and Y coordinate values received from the mouse display control unit (MLCNT) by referring to the address (ILADR, IRADR) of the one unit (SCONREC) in the screen control data table (SCONTBL) to search for the object identifier (OBJNO). Next, the screen display control unit (SCNT) transfers the detected object identifier (OBJNO) to the icon display control unit (ICNT) and thereby requests the address of an icon font to be displayed subsequently. 
     4) Thereafter, the same operation as that described in 5) and 6) in connection with FIG. 5 is executed, by which a subsequent icon font is displayed on the display (DSP). 
     The process of registration and deletion of a plurality of icon fonts and that of display of a subsequent icon font will be described below with reference to FIGS. 7 through 10. 
     FIG. 7 illustrates the contents of the icon font registration parameter (IFNTPRM) when the application program (APROG) registers a plurality of icon fonts for a single object. As shown in FIG. 7, IFNTPRM is made up of a number of icon fonts (INO) and a font pattern (IFNTP). The number of icon fonts (INO) is an area in which the number of registered font patterns (IFNTP) is indicated, and has 2 bytes. In this embodiment, since the icon font is designed to have a bit pattern of 64×64 dots, the font pattern (IFNTP) of each font has 512 bytes. A maximum of 10 icon fonts can be defined per object. 
     FIG. 8 is a flowchart showing the process of registering icon fonts executed by CPU  21 . 
     First, in step S 81 , an area whose presently displayed icon no (CDNO) in the one unit (IFNTREC) of the icon display data table (IFNTBL) is FFFFh (h indicates a hexadecimal number) is searched for. The presently displayed icon no. (CDNO) having FFFFh indicates a non-used area. 
     Next, in step S 82 , the value in the number of icon fonts (ITNO) and the value in the font pattern (IFNTP) of the registration parameter (IFNTREC) are respectively stored in the areas of the number of registered fonts (ITNO) and the registered fonts (IFNTREG) in the searched one unit (IFNTREC). Also, the position of the searched one unit (IFNTREC) in the icon display data table (IFNTBL) is set as the object identifier (OBJNO) which is the return data, by which the process is ended. 
     FIG. 9 is a flowchart showing the process of deleting the icon fonts executed by CPU  21 . 
     In step S 91 , the one unit (ICONREC) in the icon display data table (IFNTBL) is pointed to on the basis of the object identifier (OBJNO) which is an input parameter. In step S 92 , FFFFh (a deleting symbol) is set in the presently displayed icon no. (CNDO) in the pointed to ICONREC. 
     FIG. 10 is a flowchart showing the process of displaying a subsequent icon font. This process is activated by the screen display control unit (SCNT) using the object identifier (OBJNO) as a parameter when the right button of the mouse is clicked twice. 
     First, in step S 101 , the one unit (ICONREC) in the icon display data table (IFNTBL) is pointed out on the basis of the object identifier (OBJNO). In step S 102 , the value with “1” added to the presently displayed icon no. (CDNO) is compared with the value stored in the number of registered fonts (ITNO). If the value with “1” added to the presently displayed icon no. (CDNO) is larger than the value in the number of registered fonts (ITNO), “0” is set in the presently displayed icon no. (CNDO). 
     Next, in step S 103 , a subsequently displayed font address is calculated on the basis of the presently displayed icon no. (CDNO), the size of IFNTREC and the starting address of the icon display data table (IFNTBL), by which the process returns. 
     Since the value in the presently displayed icon no. (CDNO) is FFFFh when registration is performed, “1” is added to the presently displayed icon no. (CDNO) in step S 102 . This allows the common routine shown in FIG. 10 to be used for both an initial display made after initial registration and the subsequent icon font display. 
     Furthermore, in this embodiment, the 50 areas of the presently displayed icon no. (CDNO) are initialized to FFFFh when the apparatus is switched on. 
     As mentioned above, in the present embodiment, display of a plurality of icon fonts for one object at the same display position is made possible by both the function of registering a plurality of icon fonts and the function of recognizing the request for display of a subsequent icon. 
     Therefore, even when only a single icon font is displayed to express a single object, the operator can be informed of the significance of the object. Consequently, the efficiency of the operator and the user interface function can be improved. 
     In this embodiment, a personal computer has been described. However, the present invention can also be applied to, for example, a work station or a terminal device. 
     Application of the present invention to a work station can be achieved by the use of the same configuration as that of this embodiment, shown in FIGS. 1 and 2. To implement a terminal device, the application program (APROG) shown in FIG. 1 is provided on a host computer, and the terminal device has, in place of the application program shown in FIG. 1, a “function of communicating with the host computer”, which communicates with the host computer “the parameter (IFNTPRM) shown in FIG.  7 ” and “the object identifier (OBJNO) and display address”. Hence, a host communication interface for communicating with the host computer is added to the structure shown in FIG.  2 . 
     Furthermore, in this embodiment, the maximum number of icon fonts that can be registered is limited to 10. However, the limitation of the number of icon fonts that can be registered can be removed by making the size of the one unit (IFNTREC) in the icon display data table (IFNTBL) variable. 
     Furthermore, an object management, which replaces the application program shown in FIG. 1, may control a plurality of application programs at the same time to manage the object identifier and the icon display address in the same manner as that of this embodiment. 
     Furthermore, if a multiwindow-oriented screen display control unit (SCNT) or object management is provided, the subsequent icon font display function can be implemented on the multi-window as well without changing the icon display control (ICONT) function which characterizes the present invention. A multiwindow-oriented work station or terminal machine can also achieve the function of displaying a subsequent icon font. 
     In this embodiment, the font size is 512 bytes (64×64 dots). However, the font size is not fixed and can be changed freely in both width and height. In that case, the layout of the one unit (IFNTREC) in the icon display data table (IFNTBL), the layout of the registered parameter (IFNTPRM), and the processing contents of the screen display control unit (SCNT) and icon display control (ICNT) must be changed accordingly. These functions can be done easily. 
     Further, display of a subsequent icon is performed when the right button of a mouse is clicked twice. However, it may also be initiated by the operation of keys on a keyboard or by touching of a touch panel provided on a display. 
     Furthermore, an area in which font addresses in the IFNTBL are stored may be provided in the SCONREC shown in FIG. 4 so as to allow the screen display control unit (SCNT) to store the font addresses shown in FIGS. 5 and 6 in the SCONREC. In this way, the processing speed of the overall screen display or the like can be increased. 
     The present invention can be applied to either an apparatus made up of a single component or a system made up of a plurality of components. The present invention can also be applied to an apparatus or a system which is activated when the program is supplied thereto. 
     As will be understood from the foregoing description, in the present invention, since a single object can be expressed by a plurality of icons, operability and workability can be enhanced. 
     A second embodiment of the present invention will be described below with reference FIGS. 1 and 3 through  11 . The description of FIGS. 1 and 3 through  10  has already been provided with respect to the first embodiment and will be omitted. 
     FIG. 11 is a view illustrating the hardware of the block diagram of FIG. 1 in the second embodiment. FIG. 11 shows a personal computer. In FIG. 11, a microprocessor (CPU) controls the entire personal computer according to the control procedures (programs) shown in FIGS. 8 through 10, which have been described with respect to the first embodiment, and control data. A main memory (MM)  22  stores the mouse display control unit  13 , the screen display control unit  16 , the icon display control unit  17 , the application program  18 , the icon display data table  19 , the screen control data table  20 , the control procedures program and so on. A timer  23  counts a predetermined time interval when the registered icon font is displayed. A CPU bus  24  consists of an address bus, a data bus and control lines. 
     In this embodiment, the screen display control unit (SCNT) writes all the icon fonts corresponding to the object in the icon display data table (IFNTBL) managed by the icon display control unit (ICNT) at the corresponding address in the display control unit (DCNT) so as to display them on the display (DSP) at predetermined time intervals. The aforementioned time intervals are 1.5 second in this embodiment. This time is counted by the timer (TIMER) shown in FIG. 11 so as to allow the screen display control unit (SCNT) to be activated. 
     Consequently, all the icon fonts registered for the object are displayed on the display (DSP) at time intervals of 1.5 second. 1.5 second after the display of the final icon font, the icon display area (of 64×64 dots) on the display (DSP) is cleared. This lasts for 1.5 second. Thereafter, the first icon is displayed again. 
     In this embodiment, the registered icon fonts are sequentially displayed at time intervals of 1.5 second. However, it may be arranged such that the time during which each icon font is displayed is changed by the user. 
     As described with respect to the first embodiment, and the invention of the second embodiment the present invention can be applied to either an apparatus made up of a single component or a system made up of a plurality of components. The present invention can also be applied to an apparatus or a system which is activated when the program is supplied thereto. 
     As will be understood from the foregoing description, since a plurality of icons registered for a single object can be displayed at predetermined time intervals, operability and workability can be enhanced. 
     A third embodiment of the present invention will be described below with reference to FIGS. 1 through 10 and FIGS. 12 through 14. The description of FIGS. 1 through 10 has already been provided with respect to the first embodiment and will be omitted. 
     Control of display of the presently displayed/subsequently displayed icon fonts will be described below with reference to FIGS. 12 through 14. 
     FIG. 12 illustrates the process executed by the screen display control unit (SCONT) when display is switched over from the presently displayed icon to the subsequently displayed icon to select the presently displayed/subsequently displayed icon {hereinafter referred to as a target icon (TICON)} according to control data (FCNT) and then to store the selected target icon in an icon creating area (DICON). 
     As shown in FIG. 12, the target icon (TICON) consists of T 1-1  through T 1-8  and T 2-1  through T 2-8 , . . . , T 8-1  through T 8-8 . Each has 64 bits which is one unit of the present/subsequent icon font. The control data (FCNT) is used for selecting the icon fonts T 1-1  through T 8-8 . The control data (FCNT) consists of 8 data items. If the contents of the data item of the control data are “1”, selection of T 1-1  through T 8-8  is made and the selected bit is set in the icon creating area (DICON). If the contents of the data item are “0”, selection of T 1-1  through T 8-8  is not made. 
     The icon creating area (DICON) consists of d 1 , d 2 , . . . , d 64 , each of which has 64 bits. The data selected by the control data (FCNT) are set in the icon creating area in sequence starting with d 1 . 
     Arrows in FIG. 12 indicate that one unit of the target icon (TICON) is selected by the control data (FCNT) and that the selected target icon is set in the icon creating area (DICON). In other words, when the control data (FCNT) is “0”, one unit of the target icon (TICON) is not set in the icon creating area (DICON) and is discarded. 
     FIG. 13 illustrates a set of control data (FCNT) shown in FIG.  12 . In FIG. 13, f 1  is the control data which indicates 7/8 display of an icon, f 2  indicates 6/8 display of an icon, . . . , f 7  indicates 1/8 display of an icon. To sequentially reduce the present icon in the direction of the height thereof, f 1 , f 2 , , f 7  are sequentially set in the control data (FCNT) in that order. To enlarge the subsequent icon sequentially, f 7 , f 6 , . . . , f 1  are sequentially set in the control data (FCNT) in that order. 
     FIG. 14 shows data which designates the starting position of the icon creating area (DICON). To simplify the description, it has been described in connection with FIG. 12 that data is set in the icon creating area (DICON) from d 1 . However, in an actual operation, S 1  is used when f 1  is used in the control data (FCNT), S 2  is used for f 2 , and so on, to change the setting position in the icon creating area (DICON). 
     In this way, when the presently displayed icon is switched to the subsequently displayed icon, it can be displayed as if a card is turned over. 
     In this embodiment, each icon has a size of 64×64 bits. It is not reduced in the direction of width but is reduced in the direction of height. However, the icon may be divided into 8 portions in the direction of height so that the divided T 1  (T 1  through T 1-8 ), T 2  (T 2-1  through T 2-8 ), . . . , T 8  (T 8-1  through T 8-8 ) of the target icon (TICON) are selected by the same control data (FCNT). 
     As mentioned above, in the present embodiment, display of a plurality of icon fonts for one object at the same display position is made possible by both the function of registering a plurality of icon fonts and the function of recognizing the request of display of a subsequent icon. 
     Therefore, even when only a single icon font can be displayed to express a single object, the operator can know the significance of the object. Consequently, the efficiency of the operator and the user interface function can be improved. 
     In the third embodiment, the icon is reduced and enlarged in the direction of the height thereof. However, an icon may also be reduced and enlarged in the direction of the width thereof using the data shown in FIGS. 13 and 14. 
     The invention of the third embodiment can also be applied to either an apparatus made up of a single component or a system made up of a plurality of components. The present invention can also be applied to an apparatus or a system which is activated when the program is supplied thereto. 
     As will be understood from the foregoing description, in the present invention, a single object is expressed by a plurality of icons, and the presently displayed icon and the subsequently displayed icon have a relation similar to the two sides of a card so that display of the icon is switched over by turning over the presently displayed one. Consequently, operability and workability can be enhanced. 
     According to a fourth embodiment of the invention, a plurality of icon patterns can be registered for a single function, and these registered plurality of icon patterns are stored according to the function. When an instruction of switch over the presently displayed icon pattern to another icon pattern is given, the present icon pattern display is switched over to that of a subsequent icon pattern. 
     The fourth embodiment of the present invention will be described below in detail with reference to the accompanying drawings. 
     FIG. 15 is a block diagram, illustrating the structure of the display control apparatus according to the present invention. A mouse  101  is a pointing device. A mouse control unit  102  receives an electric signal representing a relative movement from the mouse  101 , converts the electric signal into a distance through which the mouse has been moved and outputs the resultant distance. A mouse display control unit  103  inputs the signal representing the moved distance from the mouse control unit  102 , and displays the cursor according to the distance through which the mouse  101  has been moved. A display  104  is a CRT in this embodiment. A display control unit  105  has, for example, a CRT controller (CRTC), and performs display control in terms of the hardware. A screen display control unit  106  receives image data whose display is requested and converts the received data into a video signal to be input to the display  104 . An icon display control unit  108  displays a predetermined icon selected from among a plurality of registered icons or registers or deletes the icons according to the instruction from the screen display control unit  106 . An application program unit  107  performs screen display, icon font registration and so on. 
     A screen control data unit  109 , managed by the screen control unit  106 , stores a screen display state including the icon display control data. In this embodiment, display control of 50 types of objects is performed. An icon display data  110 , managed by the icon display control unit  108 , stores font data for icon display and control data therefor. In this embodiment, 50 types of icons can be displayed, and  10  fonts can be registered for each type. 
     FIG. 16 is a block diagram showing the structure of a control unit of the display control apparatus shown in FIG.  15 . In FIG. 16, the same reference numerals are used to denote parts corresponding to those of FIG.  15 . FIG. 16 shows an example of a personal computer. 
     A CPU  201  is, for example, a microprocessor. A main memory  202  stores the control programs of the CPU  201  which execute the functions of the mouse display control unit  103 , the screen display control unit  106  and the icon display control unit  108 , the application program unit  107 , the icon display data unit  110 , the screen control data unit  109 , and so on. Reference symbols AB, DB and CNT respectively denote an address bus, a data bus and a control data bus. 
     FIG. 17 shows the data format of the icon display data shown in FIG.  15 . In FIG. 17,  301  indicates the entirety of the area in which the icon data on the single object is stored. 
     In FIG. 17,  311  is an area which indicates the presently displayed icon no., and has 2 bytes.  312  is an area in which a number of fonts currently registered for one type of object is stored.  313  is an area in which the registered fonts are stored. In the registered font area, 512 bytes are allocated to a single type of icon font data, and 5120 bytes are allocated so that a maximum of 10 types of icon font data can be stored therein. 
     FIG. 18 illustrates the data format of the screen control data unit  109 . 
     In FIG. 18,  401  indicates an area in which data on a single object is stored. 
       402  indicates an area in which data used to identify an object is stored. The area  402  has 2 bytes.  403  is an area in which data representing the left upper coordinate position of the icon when the icon is displayed on the display  104  is stored. In the area  403 , the addresses in both X and Y axes, each having 2 bytes, are stored in a 4 byte-area.  404  is an area in which data representing the right lower coordinate position of the icon when the icon is displayed on the display  104  is stored. In the area  403 , the addresses in both X and Y axes, each having 2 bytes, are stored in a 4 byte-area. 
     Registration of a plurality of icons for one object, deletion of the icons and sequential display of the plurality of icons representing one object will be described below with reference to the related figures. 
     FIG. 19 is a control transition diagram illustrating the control operations of registering and displaying a plurality of icon fonts for one object. 
     (1) An icon font registration parameter, which will be described in detail later, is handed from the application program unit  107  to the icon display control unit  108 . 
     (2) The icon display control unit  108  processes the icon font registration parameter received from the application program unit  107  and stores the processed data in the icon display data unit  110 . 
     (3) The icon display control unit  108  informs the application program unit  107  of the stored position in the icon display data unit  110  as the object identifier. 
     (4) The application program unit  107  hands the left upper address of the icon font on the display  104  and the object identifier to the screen display control unit  106 , and thereby requests an initial icon display of the registered object. 
     (5) The screen display control unit  106  stores both the object identifier and the display address in the screen control data unit  109   
     (6) The screen display control unit  106  hands the object identifier to the icon display control unit  108  and thereby requests the address of the icon font of the corresponding object. 
     (7) The icon display control unit  108  detects the font address corresponding to the object by referring to the icon display data unit  110  on the basis of the received object identifier, and then (8) lets the screen display control unit  106  know the detected font address. 
     (9) The screen display control unit  106  writes the icon font at the display address in the display control unit  105  corresponding to the display address on the display  104 , so that the icon is displayed on the display  104 . 
     Prior to description of icon display switch over which is achieved by the operation of a mouse, various operations of the mouse button and the corresponding functions will be described first. In this embodiment, a two-button mouse is used for the following operations. 
     1. One click of the left button: positive instruction 
     2. Two clicks of the left button: execution of the object 
     3. One click of the right button: negative instruction 
     4. Two clicks of the right button: display of a subsequent font of the icon 
     The mouse operations of Items 1, 2 and 3, which are respectively processed by the mouse control unit  102 , the mouse display control unit  103  and the screen display control unit  106  in this embodiment, have no direct relation to the present invention and description thereof is omitted. 
     The control operations when the right button is clicked twice will be described below with reference to FIG.  20 . 
     (1) and (2) When the operator (user) operates the mouse  101 , the mouse display control unit  103  detects the contents of that operation through the mouse control unit  102 . If the contents of the operation are to move the mouse, the mouse display control unit  103  writes the data on the mouse  101  in the display control unit  105  to display the icon representing the mouse  101  (or a cursor) on the display  104  according to the movement (3). 
     (4) If the data from the mouse control unit  102  indicates the button operation, the mouse display control unit  103  notifies the screen display unit  106  of both the physical address (X and Y coordinate values) of the cursor on the display  104  and the contents of the button operation (right/left button and one/two clicks). 
     (5) The screen display control unit  106  executes the process corresponding to the contents of the button operation of the mouse  101 . The single or double clicks of the left button and the single click of the right button have no direct relation to the present invention and the description thereof is omitted. If the right button is clicked twice, the screen display control unit  106 , knowing that it indicates a request of display of a subsequent icon font, determines whether the X and Y coordinate values given by the mouse display control unit  103  are within a square defined by the left upper display address  403  and the right lower display address  404  (FIG. 4) in one unit of the screen control data unit  109  . If the corresponding screen control data is detected, the object identifier  402  of that object is read out. 
     (6) The screen display control unit  106  hands the detected object identifier to the icon display control unit  108  and thereby requests the address of an icon font to be displayed subsequently. 
     (7) The icon display control unit  108  detects the font address corresponding to the object identifier by referring to the icon display data unit  110 , and then lets the screen display control unit  106  know of the detected font address (8). 
     (9) The screen display control unit  106  controls switch over of the present and subsequent icon fonts on the display  104  by making a continuous card on which the presently displayed icon font and the subsequently displayed icon font are slid in the display window having the size of one card. Hence, the screen display control unit  106  writes the data obtained by combining suitable portions of the two icon fonts at the corresponding address on the display control unit  105  so as to display it on the display  104  (how the data is written will be described later with reference to FIG.  25 ). 
     In the processes executed by the mouse control unit  102 , the mouse display control unit  103 , the display control unit  105 , the processes other than those of registering a plurality of icon fonts and of displaying the subsequent icon font are known and description thereof is omitted. 
     The process executed by the icon display control unit  108  for registration and deletion of a plurality of icon fonts and for display of a subsequent icon font will be described below with reference to FIGS. 22 through 25. 
     FIG. 21 illustrates the contents of the icon font registration parameter when the application program unit  107  registers a plurality of icon fonts for a single object. 
     As shown in FIG. 21, the parameter is made up of a number of icon fonts  701  and a font pattern  702 . The number of icon fonts  701  is an area in which the number of registered font patterns is indicated, and has 2 bytes. In this embodiment, since the icon font is designed to have a bit pattern of 64×64 dots, the font pattern of each font has 512 bytes. A maximum of 10 icon fonts can be defined per one type of icon. 
     The process executed by the icon display control unit  108  for registration, deletion and display of a subsequent icon font will be described below with reference to FIGS. 22 through 25. 
     FIG. 22 is a flowchart showing the process of registering icon fonts. 
     First, in step S 801 , an area whose icon no.  311  of the icon data  301  in the icon display data  110  is FFFFh (h indicates a hexadecimal number) is searched for. The icon no.  311  having FFFFh indicates a non-used area. Next, in step S 802 , the value in the number of icon fonts  701  and the value in the font pattern  702  shown in FIG. 21 are respectively stored in the areas of the number of registered fonts  312  and registered fonts  313  in the searched icon data. Also, the position of the searched icon data in the icon display data  110  is set as the object identifier which is the return data, by which the process is ended. 
     FIG. 23 is a flowchart showing the process executed by the icon display control unit  108  to delete the icon fonts. 
     In step S 901 , the icon data in the icon display data  110  is pointed on the basis of the object identifier which is an input parameter. In step S 902 , FFFFh (a deleting symbol) is set in the icon no.  311  of the pointed icon data. 
     FIG. 24 is a flowchart showing the process executed by the icon display control unit  108  to display a subsequent icon font. This process is activated by the screen display control unit  106  using the object identifier as a parameter when the right button of the mouse is clicked twice. 
     First, in step S 1001 , the icon data  301  in the icon display data  110  is pointed out on the basis of the object identifier. In step S 1002 , “1” is added to the icon no.  311  of the pointed icon data  301 , and the resultant value is compared with the value stored in the number of registered fonts  312  in step S 1003 . If the value with “1” added to the icon no. is larger, “0” is set in the displayed icon no.  311  in step S 1004 . 
     In step S 1005 , a subsequently displayed font address is calculated on the basis of the displayed icon no.  311 , the size of the icon data and the starting address in the icon display data unit  110 , by which the process returns. 
     Since the value in the icon no.  311  is FFFFh when registration is made, “1” is always added to the icon no.  311  in step S 1002 . This allows the common routine shown in FIG. 24 to be used for both initial display made after initial registration and the subsequent icon font display. Hence, in this embodiment, FFFFh is initially set in the 50 areas of the icon no.  311  when the apparatus is switched on. 
     FIG. 25 is a flowchart of the process executed by the screen display control unit  106  to display on the display  104  through the display control unit  105  two icon fonts, the presently and subsequently displayed icon fonts, as if they are scrolled as one icon font. 
     First, in step S 1101 , initialization of the entire control is performed. In this embodiment, “64 is assigned to a variable LOOP as the value of controlling the number of rasters in the direction of the height of an icon, and “1” is assigned to a variable N to control the display ratio between the presently displayed font and the subsequently displayed font. 
     Next, in step S 1102 , “0” is assigned to a variable I to control the address in the display control unit  105  at which the presently displayed icon font/subsequently displayed icon font are written. Also, the value of N is assigned to a variable J to control which raster in the presently displayed icon (“0” is given to the uppermost raster) is transferred to the display control unit  105 . In step S 1103  to S 1106 , the presently displayed icon is stored in the display control unit  105  and thereby displayed on the display  104  in such a manner that it is gradually erased from the upper portion thereof. That is, in step S 1103 , a value obtained by subtracting the value of the variable N from the variable LOOP is assigned to a variable LOOPX. Hence, the value in the variable LOOPX is decremented from 63 to 62, . . . , 0. In step S 1104 , it is determined whether or not a font obtained by moving the presently displayed icon in the direction of the height thereof by one raster has been displayed. If the answer is yes, the process goes to step S 1107 . If the answer is no, the process of step S 1105  is executed. 
     In step S 1105 , one raster of the icon font obtained by moving the presently displayed icon in the direction of the height thereof by one raster is transferred to the display area (TVRAM[ 1 ]) of the display control unit  105 . In step S 1106 , “1” is assigned to both I and J, “1” is subtracted from the variable LOOPX, and the process goes to step S 1104 . In step S 1107  to S 1110 , an icon font to be subsequently displayed is transferred to the display control unit  105  at an address subsequent to that of the presently displayed icon font and is thereby displayed on the display  104 . 
     In step S 1107 , the value of the variable N is assigned to the variable LOOPX to control the number of rasters in the subsequently displayed icon font which are transferred to the display control unit  105 . Also, “0” is assigned to the variable J. The variable J controls how many rasters of the subsequently displayed icon fonts are transferred to the display control unit  105  at the address subsequent to that of the presently displayed font icon. 
     In step S 1108 , it is determined whether or not all of the subsequently displayed icon is transferred. If the answer is yes, the process goes to step S 1111 . If the answer is no, the process of step S 1109  is executed. In step S 1109 , one raster of an icon font obtained by moving the subsequently displayed icon by one raster in the direction of the height thereof is transferred to the display area (TVRAM[ 1 ]) of the icon font display control unit  105 . Next, in step S 1110 , “1” is added to both I and J, “1” is subtracted from the variable LOOPX, and the process goes to step S 1108 . 
     In step S 1111 , the wait subroutine is called to allow the process to be suspended at that step for a predetermined period of time. Since the function of suspending the process for the predetermined period of time is known, description thereof is omitted. After the predetermined period of time has elapsed, the process goes to step S 1112 . In step S 1112 , “1” is added to the variable N, and “1” is subtracted from the variable LOOP. 
     In step S 1113 , it is determined whether or not the value of the variable LOOP is “0”. “0” in the variable LOOP indicates that the presently displayed icon has been smoothly replaced by the subsequently displayed icon. 
     In this embodiment, the personal computer has been described. However, the present invention can also be applied to, for example, a work station or a terminal machine. To implement a terminal machine, the application program unit  107  shown in FIG. 15 is provided in a host computer, and the terminal machine has, in place of the application program shown in FIG. 15, a “function of communicating with the host computer”, which communicates with the host computer “the font patterns shown in FIG.  21 ” and “the object identifier and display address”. Hence, a host communication interface for communicating with the host computer is added to the structure shown in FIG.  16 . 
     Furthermore, in this embodiment, the maximum number of icon fonts that can be registered is limited to 10. However, the limitation to the number of icon fonts that can be registered can be removed by making the size of the icon data in the icon display data variable. 
     Furthermore, an object management, which replaces the application program  107 , may control a plurality of application programs at the same time so as to manage the object identifier and the icon display address in the same manner as that of this embodiment. 
     Furthermore, if a multiwindow-oriented screen display control unit  106  or object management is provided, the subsequent icon font display function can be implemented on the multi-window as well without changing the icon display control function which characterizes the present invention. A multiwindow-oriented work station or terminal machine can also achieve the function of displaying a subsequent icon font. 
     In this embodiment, the font size is 512 bytes (64×64 dots). However, the font size is not fixed. 
     Furthermore, display of a subsequent icon is performed when the right button of a mouse is clicked twice. However, it may also be initiated by the operation of keys on a keyboard or by touching of a touch panel provided on a display  104 . 
     Furthermore, an area in which font addresses stored in the icon display data unit  110  are stored may be provided in the screen control data  401  shown in FIG. 18 so as to allow the font addresses (8) shown in FIGS. 19 and 20 to be stored in the screen control data  401 . In this way, the processing speed of the overall screen display or the like can be increased. 
     In the flowchart shown in FIG. 25, the presently displayed icon and the subsequently displayed icon are smoothly scrolled in the direction of the height thereof. However, they may also be scrolled in the direction of the width thereof. 
     In step S 1104  through S 1106  and S 1107  through S 1110  shown in FIG. 25, transfer of the font data is performed in the software. However, it may be processed by hardware (a hardware chip for transferring bits) for transferring the fonts. 
     The present invention can be applied to either an apparatus made up of a single component or a system made up of a plurality of components. The present invention can also be applied to an apparatus or a system which is activated when the program is supplied thereto. 
     As mentioned above, in the present embodiment, a plurality of icon fonts can be registered for one object, and the plurality of icon fonts can be displayed for one object by switching over icon display. 
     As will be understood from the foregoing description, in the present embodiment, a plurality of icon patterns can be registered for one object (or one function), and the object (or the function) can be explained using the plurality of icon patterns by switching over the icon pattern to be displayed to express the object (or the function).