TITLE OF THE INVENTION Information Processing Apparatus and Method, and Information Processing Program BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an information processing apparatus and method, and an information processing program, and more particularly, to an information processor, information processing method and an information processing program, adapted to execute a desired processing by a simple operation using a jog dial for example. Description of the Related Art Recently, mere have been proposed operating systems fora computer including peripheral devices such as a mouse, keyboard, video display, etc. and a central processing unit (CPU). Typical ones of such operating systems are Windows 95 and Windows 98 (trademark), trademarks of the Microsoft Corporation, USA. These operating systems provide a taskbar for each application having an active window, by which the user can have visual mnemonics like buttons. The technique directed to the use of such a taskbar is disclosed in detail in the Japanese Published Application No.8-255066. The use of the taskbar will further be described below by referring to the above Japanese Published Application. Serving as a visual mnemonic, the taskbar can be used to give the user information on a currently active window and display the active window. The taskbar includes a start menu button for enabling the user to access a menu m order to control program launching, document opening and system setting. Operation of the start menu button on the taskbar in a computer system includes examples which will be described herebelow. The start menu button opens a start menu as a home position for the user to access a program, document, system setting information, help information, etc. By moving the mouse until the on-screen cursor points to the start menu button and clicking on the left button of the mouse, the start menu will be opened on the screen. The start menu includes menu items such as "PROGRAM", "FIND", "SET', "HELP", etc. Selecting the "PROGRAM" menu item in the start menu will permit access from the start menu to a program menu having a hierarchical structure. The program menu includes a plurality of user-selectable application programs and program groups. It should be reminded that after the user selects a desired application program in the task bar with the start menu button, he or she wiH have to repeat complicated operations until the selected application program starts to run. That is, first the user moves the mouse to point the on-screen cursor to the start menu button on the taskbar and clicks on the left button of the mouse to open the start menu. Next, the user moves the mouse to point the cursor to the menu item "PROGRAM" in the start menu and clicks on the left mouse button to open the program menu. Then, the user moves the mouse to point the cursor to a desired application program displayed in the program menu and clicks on the loft mouse button. In case the user has selected an application program group in the same manner, the user will have to repeatedly point the cursor and click on the mouse cursor. Thereafter, the CPU will put the desired application program into run. As in the above, the user has to repeat such complicated operations until his desired application program starts to run. Namely, the taskbar is not any easy tool as a user interface. This is also true for doing a desired operation by clicking a menu item such as "HELP" in the start menu program. Also, the taskbar cannot implement any user's desire to readily view an electronic mail in the computer or to start a desired application software. OBJECT AND SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art by providing an information processor, infonnation processing method, and an infonnation processing program, capable of executing a desired processing immediately by a simple operation using a jog dial for example. It is another object of the present invention to provide an infonnation processor, infonnation processing method, and an information processing program, capable of undoing an operation once done by pushing a jog dial, for facilitating the user to do operations. According to the present invention, there is provided an information processor for processing information signal based on an application program and displaying a result and process of the processing operation on a display unit, the apparatus including a first operating means which can be rotated and pushed, a second operating means for undoing an operation once done by pushing the first operating means, and a controlling means for monitoring the operated status of the first and second operating means and displaying an operation window corresponding to each of the operations made with the operating means on the display unit according to a status of the application program. According to the present invention, there is also provided an information processing method for processing information signal based on an application program and displaying a result and process of the processing operation on a display unit, the method including steps of monitoring the operated status of a first operating means which can be rotated and pushed, and that of a second operating means which can undo an operation once done by pushing the first operating means, and displaying an operation window corresponding to each of the operations made with the first and second operating means on die display unit. According to die present invention, there is also provided an information processingprogram for processing information signal based on an application program and displaying a result and process of the processing operation on a display unit, the method including steps of monitoring the operated status of a first operating means which can be rotated and pushed, and that of a second operating means which can undo an operation once done by pushing the first operating means, and displaying an operation window corresponding to each of the operations made with the first and second operating means on the display unit. According to the present invention, there is also provided an information processor for processing information signal based on an application program and displaying a result and process of the processing operation on a display unit, the apparatus including an operating means which can be rotated and pushed, and a controlling means for monitoring the operated status of the operating means and displaying an operation window corresponding to each of the operations made with the operating means on the display unit according to a status of the application program, the controlling means detecting a first pushed status of the operating means, in which the operating means has not been pushed for a time longer than a predetermined length of time and a second pushed status of the operating means, in which the operating means has been pushed for the time longer than the predetermined length of time, as differentiated between them, and undoing an operation once done because the first pushed status has been detected when the second pushed status is detected. According to the present invention, there is also provided an information processing method for processing information signal based on an application program and displaying a result and process of the processing operation on a display unit, the method including steps of monitoring whether an operating means which can be rotated and pushed has been operated, receiving a notice of the monitoring that the operating means has been operated, and then differentiating between a first pushed status of the operating means, in which the operating means has not been pushed for a time longer than a predetermined length of time, and a second pushed status of the operating means, in which the operating means has been pushed for the time longer than the predetermined length of time, effecting an operation based on a result of the differentiation, and displaying a result of the operation based on the result of differentiation on the display unit. According to the present invention, there is also provided a program for processing information signal based on an application program and displaying a result and process of the processing operation on a display unit, the program including steps of monitoring whether an operating means which can be rotated and pushed has been operated, receiving a notice of the monitoring that the operating means has been operated, and then differentiating between a first pushed status of the operating means, in which the operating means has not been pushed for a time longer than a predetermined length of time, and a second pushed status of the operating means, in which the operating means has been pushed for the time longer than the predetermined length of time, effecting an operation based on a result of the differentiation, and displaying a result of the operation based on the result of differentiation on the display unit. According to the present invention, an operation once done by pushing the first operating means can be redone simply by pressing the second operating means, which enables the user to operate the information processor more easily. Also, according to the present invention, an operation once done by pushing the rotating and pushing type operating means can be redone by a software, without having to provide any hardware provided to this end, through judgment of whether the means has been pushed for a time longer than a predetermined one. These objects and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective external view of a notebook PC (personal computer) in which the present invention is applied; FIG. 2 is a plan view of the notebook PC in FIG. 1, showing essential portions of the notebook PC as enlarged in scale; FIG. 3 is a side elevation of the notebook PC in FIG. 1, showing the essential portions of the notebook PC; FIG. 4 is a perspective external view of a jog dial; FIG. 5 is a perspective external view of a contact carrying board being an essential portion of the jog dial in FIG. 4; FIG. 6 is a front, sectional view of the jog dial in FIG. 4; FIG. 7 is a side, sectional view of the jog dial in FIG. 4; FIG. 8 is a side elevation of a device in which the jog dial in FIG. 4 is provided, showing the installation of the jog dial to the apparatus; FIG. 9 is a partially fragmentary top view of the jog dial in FIG. 4, showing a rotary encoder used in the jog dial; FIG. 10 is a top view of a push switch of the jog dial in FIG. 4; FIG. 11 is a perspective external view of another notebook PC in which the present invention is applied; FIG. 12 is a plan view of the notebook PC in FIG. 11, showing essential portions of the notebook PC as enlarged in scale; FIG, 13 is a perspective external view of a still another notebook PC in which the present invention is applied; FIG. 14 is a side elevation of the still another notebook PC in FIG. 12; FIG. 15 is an electric circuit diagram of the notebook PC whose appearance is shown in FIG. 1, FIG. 16 is a functional block diagram showing monitoring by an embedded controller of the jog dial and a back button; FIG, 17 is a Dow chart of operations effected when the embedded controller executes a jog dial status monitoring program; FIG. 18 is a time chart of operations of a rotary detector shown in FIG. 17; FIG. 19 is a flow chart of operations effected by a CPU in the notebook PC when executing a jog dial- or back button-status monitoring program after a power switch is turned on; FIG. 20 shows a jog-dial window in detail; FIG. 21 shows an example of the display by a map-display application program; FIG. 22 shows another example of the display by the map-display application program; FIG. 23 is a flow chart of operations effected when the back button is pressed; FIG. 24 shows an appearance of a mobile telephone which is a second embodiment of the present invention; FIG. 25 shows an appearance of a portable digital assistant (PDA) which is a third embodiment of the present invention; FIG. 26 shows an appearance of a notebook PC which is a fourth embodiment of the present invention; FIG. 27 is a plan view of the notebook PC which is the fourth embodiment of the present invention, showing essential portions as enlarged in scale; FIG. 28 shows an example of the electric circuit construction of the notebook PC which is the fourth embodiment of the present invention; FIG. 29 is a functional block diagram of monitoring by an embedded controller of a jog dial, in the notebook PC which is the fourth embodiment of the present invention; FIG. 30 is a flow chart of operations effected when a CPU in the notebook PC which is the fourth embodiment of the present invention executes a jog dial status monitoring program after the power switch is turned on; FIG. 31 is a flow chart of operations effected when the jog dial of the notebook PC which is the fourth embodiment of the present invention is pushed for more than 1 second; FIG, 32 shows examples of the display by a graphical user interface; FIG. 33 shows an example of the display by a map-display application program; FIG. 34 shows another example of the display by the map-display application program; FIG. 35 is a plan view of a portable digital assistant (PDA) which is a fifth embodiment of the present invention; and FIG. 36 is a perspective view of a mobile telephone which is a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A notebook personal computer (PC) as the first embodiment of the present invention in which the information processor, information processing method and information processing prop-am according to the present invention are applied, will be described first with reference to FIGS. 1 to 23. FIGS, I to 3 schematically shows the notebook PC. The notebook PC is generally indicated with a reference I, As shown, the notebook PC 1 is essentially composed of a body unit 2 and a display unit 3 installed to the body unit 2 so that it can be freely opened and closed, FIG. 1 is a perspective external view, showing the display unit 3 opened from the body unit 2. FIG. 2 is a pian view of the display unit 3. FIG, 3 is a side elevation, showing the display unit 3 closed to the body unit 2. The body unit 2 of the notebook PC 1 has provided on the top surface thereof a keyboard 6 which is operated for entering various characters and symbols, a touch pad 7, as a pointing device, which is operated for moving an on-screen mouse cursor and for similar purposes, and a power switch 9 to turn on and off the notebook PC I. The display unit 3 has a jog dial 4 (a first operating means) and a back button 5 (second operating means) provided vertically at the right upper corner thereof. The jog dial 4 can be rotated and pushed. The back button 5 is to undo an operation having been made by pushing the jog dial 4, and it is located near the jog dial 5 as shown. Further, the display unit 3 has an LCD (liquid crystal display) 8 to display an image. Moreover, the display unit 3 has provided horizontally at the right upper corner thereof a pilot lamp PL, battery lamp BL, other lamps and a message lamp ML (provided as necessary). Each of these lamps is an LED (light emitting diode). Next, the jog dial 4 will further be described. The jog dial 4 can be turned in directions of arrows a. and c (counterclockwise and clockwise, respectively) as shown in FIG. 2, and also can be pushed in the direction of arrow h also in FIG 2. Each of the clockwise and counterclockwise turns and pushing of the jog dial 4 allows a predetermined operation to be done. The predetermined operations allowed by operating the jog dial 4 will be described later. First, the construction of the jog dial 4 will be described. This jog dial 4 is an embodiment of the rotary electronic part with a push switch, disclosed in the Japanese Published Application No. 8-2033S7 filed by the co-applicant of the present invention. That is, the jog dial 4 includes a rotary encoder 12 and push switch 13 disposed on a contact carrying board 11 as shown in FIG. 4. The rotary encoder 12 is movable horizontally within a predetermined range, but the push switch 13 is fixed against movement. As shown in FIG. 5, the contact carrying board 11 is a molded resin board having formed therein concavities 15 and 17. The concavity 15 has guide rails 14 provided along the lateral sides thereof and opposite to each other, and along which the rotary encoder 12 is movable. A stop wall 16 is provided in the concavity 17 to secure the push switch 13. Also, contact strips I9 each with a terminal 18 are provided in the concavity 17 to transmit an electric signal from the rotary encoder 12 to outside. As shown in FIGS. 6 and 7, the rotary encoder 12 is composed of a box-like case 20, elastic contact legs 21 and 22, rotor 25 and a disc-like control knob 27. The case 20 is a resin molding. It is fitted in the concavity 15 formed in the contact carrying board 11 and held therein by the guide rails 14 to be movable in a horizontal direction (in the direction of arrow HI in FIGS. 4 and 7) within a predetermined range. The elastic contact legs 21 and 22 are projected upward and downward, respectively, from an elastic contact block 45 installed to die bottom surface of the box case 20 by insert-molding. The rotor 25 is also a resin molding. It is held rotatably on a cylindrical shaft 23 formed integrally in the middle of the box case 20 and has circularly and radially disposed disc-like contact strips 24. The clastic contact legs 21 arc in clastic contact with the lower side of the rotor 25. The disc-like control knob 27 is fixed to the top of the rotor 25 with a screw 26 to rotate the rotor 25. The control knob 27 is to be rotated with fingers applied the lateral periphery thereof Further, a pin-like projection 28 is provided on the contact carrying board 11 (see FIGS. 5 and 9) to position a torsion coil spring 29 The torsion coil spring 29 presses the lateral side of the box case 20 so that the rotary encoder 12 is normally forced away from the push switch 13 while die elastic contact legs 22 projected downward from the bottom of the box case 20 arc kept in clastic contact with the contact strips 15 on the contact carrying board 11. As shown in FIGS. 4 and 5, the push switch 13 has an operating button 30 fitted and fixed in th concavity 17 of the contact carrying board 11 to be opposite to the rotary encoder 12 and abut at the read end thereof the stop wall 16. As best shown in FIG. 1, the box case 20 of the rotary encoder 12 has a driving projection 31 formed integrally therewith and which abuts the end of the operating button 30 of the push switch 13. The jog dial 4 is constructed as in the above. The jog dial 4 is installed to an electronic device as follows. As shown in FIG. 8, legs 11A and 1 IB formed at the bottom of the contact carrying board 11 are detent-inserted into fixing holes 34 A and 34B formed in a printed wiring board 33 of the electronic device, the connecting terminals 18 of the rotary encoder 12 are inserted into fixing holes 35 in the printed wiring board 33, and connecting terminals 32 provided to the push switch 13 are inserted into fixing holes 36 in the printed wiring board 33. The terminals 18 and 32 thus inserted in the respective fixing holes 35 and 36 are fixed there by soldering. The disc-like control knob 27 of the rotary encoder 12 is installed to the electronic device with the end thereof opposite to the push switch 13 projected out of a slot formed in an outer case 37 of the electronic device as also shown in FIG. 8. The jog dial constructed as in the above functions as will be described below. As shown in FIGS. 8 and 9, as the disc-tike control knob 27 installed to the top of the rotary encoder 12 is turned by applying a force tangentially to a portion 27 A thereof projecting from the outer case 37 of the electronic device, the rotor 25 is rotated about the cylindrical shaft 23 in the middle of the box case 20 while the upper elastic contact leg 21 are slid in elastic contact with and on the radially and circularly disposed contact strips 24 on the lower side of the rotor 25, whereby each point of contact between the contact leg 21 and strip 24 produce a pulsed signal synchronous with the rotation of the disc-like control knob 27. The pulse signal is transmitted from the upper elastic contact leg 21 to the lower elastic contact leg 22 and further to the contact strip 19 on the contact carrying board 11 with which the elastic contact leg 22 is in elastic contact, and then it is transmitted to a circuit formed on the printed wiring board 33 in the electronic device via the external connection terminal 18. When a pressure is applied to the projecting portion 27 A of the disc-like control knob 27 in a horizontal direction connecting the center of the knob 27 and the push switch 13 (in the direction of arrow H2) against the force of the torsion coil spring 29 above the contact carrying board 11 as shown in FIG. 10 (that is, when the control knob 27 is pushed in), the whole rotary encoder 12 is moved horizontally along the guide rails 14 on the contact carrying board 11 and thus the driving projection 31 formed integrally with the box case 20 pushes the operating button 30 to activate the push switch 31 which will thus produce a signal. The signal from the push switch 13 is transmitted to the circuit on the printed wiring board 33 in the electronic device via the connecting terminal 32 shown in FIG. 8. When the pressure applied to the disc-like control knob 27 is removed (that is, when the control knob 27 is released), the rotary encoder 12 is forced back to the home position as shown in FIG. 9 under the action of an elastic restoring force of the torsion coil spring 29 provided above the contact carrying board 11. For transmission of an electric signal from the rotary encoder 12 to the connecting terminals 18 of the contact carrying board 11, the elastic contact legs 22 projecting downward from the bottom of the box case 20 of the rotary encoder 12 are put into elastic contact with the contact strips 19 on the bottom of the contact carrying board 11 as in the above. Note however that the present invention is not limited to the above arrangement of the contacts but upward projecting elastic contact legs may be provided on the contact carrying board 1 i while contact strips may be disposed on the lower side of the box case 20 so that the contact legs can be put into elastic contact with the contact strips. The back button 5 undoes an operation having been effected by pushing the jog dial 4. It is located in the vicinity of the jog dial 4. The jog dial 4 and back button 5 are located at the right upper comer of the display unit 3 as shown in FIGS. 1 to 3. When pressed in the direction of arrow