Abstract:
A disc reproducing apparatus reproduces information as a digital signal from a disc, having an interface for sending and receiving a reproduction signal and a command to/from a host computer, comprising a processor unit for controlling the operation of the disc reproducing apparatus, a first signal transfer path, connected to the inter-face, for transferring a command signal corresponding to a command received from the host computer to the processor unit, an operating unit, disposed in the disc reproducing apparatus, for generating an operation signal corresponding to a user&#39;s operation, and a second signal transfer path, connected to the operating unit, for transferring an operation signal corresponding to the user&#39;s operation of the operating unit to the processor unit, wherein the processor unit determines whether or not to validate the execution of the command of the command signal transferred from the host computer through the first signal transfer path corresponding to the operation signal transferred from the operating unit through the second signal transfer path. Since the content of the operation of the disc reproducing apparatus can be freely selected by the user, even if a computer virus knows the command execution restricting function, the computer virus does not know the content of the operation of the operating portion.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a command executing method of an information reproducing apparatus, a record medium for recording a program that causes an information reproducing apparatus to execute a command, and a disc reproducing apparatus for reproducing data from an optical disc such as a CD-ROM or a DVD. 
     2. Description of the Related Art 
     In recent years, as data communications using public telephone lines such as Internet are becoming common, computer viruses that are programs that are not issued by users cause computer systems to malfunction and are becoming serious social problems. 
     Most of peripheral units such as a CD-ROM drive and a DVD drive that are operated corresponding to commands received from host computers cannot know whether such commands have been infected by computer viruses. Thus, the peripheral units simply receive and execute the programs infected by computer viruses. 
     To prevent an optical disc drive such as a CD-ROM drive or a DVD drive from being operated with a program infected by a computer virus, a method for restricting the operation of the optical disc drive with a password designated to each user or each disc title has been proposed. 
     However, in such an optical disc drive, a program infected by a computer virus may cause setting information such as a password to be erased or forged. Once an optical disc drive is infected by a computer virus, the optical disc drive may not be used. 
     In such circumstances, a means for securely protecting an optical disc drive from a program infected by a computer virus has been desired. 
     SUMMARY OF THE INVENTION 
     The present invention is made from the above-described point of view. An object of the present invention is to provide a disc reproducing apparatus that prevents a command of a virus-infected program that resides in a computer system from being executed. 
     Another object of the present invention is to provide a command executing method for an information reproducing apparatus so as to prevent a virus-infected program that resides in a computer system from disturbing the operation of the information reproducing apparatus. 
     A further object of the present invention is to provide a record medium for recording a program that causes an information reproducing apparatus to prevent a virus-infected program that resides in a computer system from disturbing the operation of the information reproducing apparatus. 
     The present invention is a command executing method of an information reproducing apparatus, comprising the steps of receiving through a first transfer path a command for managing the operation of a reproducing portion that reproduces information, determining whether or not to validate the execution of the command received through the first transfer path corresponding to information obtained through a second transfer path, and executing the command when the execution of the command is validated. 
     Thus, according to the present invention, as a condition for executing a command issued from a command generating unit of a host unit or the like, since a command received from a path that the command generating unit does not know is added, a command forged by a computer virus that resides in the command generating unit can be prevented from being executed. Consequently, a disc reproducing apparatus that is highly secured can be provided. 
     These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a front perspective view showing an appearance of an optical disc drive according to an embodiment of the present invention; 
     FIG. 2 is a rear perspective view showing an appearance of the optical disc drive according to an embodiment of the present invention; 
     FIG. 3 is a block diagram showing the structure of a computer system having an optical disc drive as a peripheral unit according to an embodiment of the present invention; 
     FIG. 4 is a state transition diagram showing a command transfer process of an optical disc drive according to a first embodiment of the present invention; 
     FIG. 5 is a flow chart showing an operation process of a command generating unit of a host computer according to the first embodiment of the present invention; 
     FIG. 6 is a schematic diagram showing the content of an output screen according to the first embodiment of the present invention; 
     FIG. 7 is a flow chart showing a command execution restricting process of a controlling portion of the optical disc drive according to the first embodiment of the present invention; 
     FIG. 8 is a state transition diagram showing a command transfer process of an optical disc drive according to a second embodiment of the present invention; 
     FIG. 9 is a flow chart showing an operation process of a command generating unit of a host computer according to the second embodiment of the present invention; 
     FIG. 10 is a schematic diagram showing the content of an output screen according to the second embodiment of the present invention; 
     FIG. 11 is a flow chart showing a command execution restricting process of a controlling portion of the optical disc drive according to the second embodiment of the present invention; 
     FIG. 12 is a flow chart showing an operation process of a command generating unit of a host computer according to a third embodiment of the present invention; 
     FIG. 13 is a schematic diagram showing the content of an output screen according to the third embodiment of the present invention; 
     FIG. 14 is a flow chart showing a command execution restricting process of a controlling portion of the optical disc drive according to the third embodiment of the present invention; 
     FIG. 15 is a schematic diagram showing an example of disc type information of the optical disc drive according to the third embodiment of the present invention; 
     FIG. 16 is a schematic diagram showing the concept of a thin (drawer) type driving unit of an optical disc drive according to an embodiment of the present invention; and 
     FIG. 17 is a schematic diagram showing the concept of a thick (tray) type driving unit of an optical disc drive according to an embodiment of the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Next, with reference to the accompanying drawings, embodiments of the present invention will be described. 
     FIGS. 1 and 2 are front and rear perspective views showing appearances of an optical disc drive according to an embodiment of the present invention. As shown in FIGS. 1 and 2, the optical disc drive  10  has a disc carrier  11 , an ejection button  12 , an LED  13 , an operation mode setting jumper pin  14 , a cable connector  15 , and a power supply connecting portion  16 . The ejection button  12  is used to eject (unload) a disc loaded in the optical disc drive  10 . The LED  13  is used to display an operation state of the optical disc drive  10 . The cable connector  15  is used to connect the optical disc drive  10  to a computer. The power supply connecting portion  16  is used to connect the optical disc drive  10  to a power cable. A disc is rotatably set to the disc carrier  11 . The disc carrier  11  has a driving mechanism that carries a disc between a user disc access position and an optical pickup disc access position. The driving mechanism is composed of various electric and mechanical parts such as a motor, a gear, and a lever. At the user disc access position, the user can set a disc. At the optical pickup accessing position, the disc is accessed by an optical pickup. The disc carrier  11  is largely categorized as a tray type, a drawer type, a cassette type, and a slot-in type. In the tray type disc carrier, only a disc space is formed. In the drawer type disc carrier, a disc driving/reproducing mechanism is disposed. In the cassette type of disc carrier, a disc is housed in a cassette. Users insert the disc cassette into the disk by hand. In the slot-in type disc carrier, a disc is directly loaded to the optical disc drive. 
     FIG. 3 is a block diagram showing the structure of a computer system connected to the optical disc drive  10 . As shown in FIG. 3, the computer system  20  comprises a host computer  21 , an inputting unit  25 , an outputting unit (not shown), an optical disc drive  10 , a communication unit (not shown), and a magnetic disk drive (not shown). An OS (Operating System)  24  is pre-installed to the host computer  21 . The inputting unit  25  includes for example a keyboard and a mouse. The outputting unit includes for example a display and a printer. The communicating unit is for example a modem. The magnetic disc drive includes for example a hard disk drive and a floppy disk drive. 
     The optical disc drive  10  comprises a program storage type of controlling portion  26 , a communication controlling portion  27 , an ejection switch  31 , and a disc reading/reproducing portion  33 . The ejection switch  31  causes a tray access command corresponding to the operation of the ejection button  12  (shown in FIG. 1) to notify to the controlling portion  26 . 
     The host computer  21  has a command generating unit  23 . The command generating unit  23  generates a command to cause the controlling portion  26  of the optical disc drive  10  to execute under the control of the OS  21 . A command generated by the command generating unit  23  is transferred to the controlling portion  26  of the optical disc drive  10  through the communication controlling portion  27  as an interface. 
     The controlling portion  26  of the optical disc drive  10  is composed of a command executing portion  28 , a command validity determining portion  29 , and an operation detection/counter portion  30 . When the controlling portion  26  receives a command generated by the command generating unit  23 , the command validity determining portion  29  determines whether or not the received command is valid. In other words, the command validity determining portion  29  compares operation setting information that the user pre-sets to the optical disc drive  10  with operation detection information detected by the operation detection/counter portion  30 . When the received command is valid, the command validity determining portion  29  sends the command to the command executing portion  28 . The command executing portion  28  executes the command. 
     Next, the setting method for the operation setting information will be described. The controlling portion  26  of the optical disc drive  10  can directly monitor a user&#39;s operation of the ejection switch  31  of the optical disc drive. The controlling portion  26  monitors the number of times of the operation of the ejection switch  31  and stores data thereof to the operation detection/counter portion  30 . The operation detection/counter portion  30  is composed of a nonvolatile memory or the like. 
     The disc reading/reproducing portion  33  causes the optical pickup to read a signal recorded on a disc corresponding to a command transferred from the host computer  21 . Thereafter, the disc reading/reproducing portion  33  demodulates and reproduces the signal that is read from the disc. Generally, the disc reading/reproducing portion  33  is composed of the above-described optical pickup, an optical pickup driving portion, a motor portion, a system controlling portion, a demodulating portion, and an error correcting portion. The optical pickup driving portion drives the optical pickup. The motor portion rotates the disc. The system controlling portion controls the entire system. The demodulating portion demodulates a signal that is read from the disc and extracts demodulated data. The error correcting portion corrects an error of the data. 
     Next, embodiments of the present invention will be described. 
     (1) First Embodiment 
     Next, with reference to FIGS. 4 to  7 , a first embodiment of the present invention will be described. 
     FIG. 4 is a state transition diagram showing a command transfer process of an optical disc drive according to a first embodiment of the present invention. FIG. 5 is a flow chart showing an operation process of a command generating unit of a host computer according to the first embodiment of the present invention. FIG. 6 is a schematic diagram showing the content of an output screen according to the first embodiment of the present invention. FIG. 7 is a flow chart showing a command execution restricting process of a controlling portion of the optical disc drive according to the first embodiment of the present invention. 
     As shown in FIG. 4, the user inputs a predetermined start command (for example, a command “Reset drv” shown in FIG. 6) to the host computer  21  with the inputting unit  25  (for example, the keyboard). The OS  24  installed in the host computer  21  receives the start command and activates the command generating unit  23 . 
     As shown in FIG. 5, when the command generating unit  23  gets started, it sends a first command to the OS  24 . (step  50 ). 
     Just after the command generating unit  23  gets started, it generates the first command. For example, the first command causes the optical disc drive  10  to start. 
     After the command generating unit  23  has generated the first command, as shown in FIG. 6, the command generating unit  23  displays on the display for example a message “PRESS THE EJECTION BUTTON TWICE OR MORE” that prompts the user to perform the required operation with. (step  51 ) 
     As shown in FIG. 7, the first command that is sent to the OS  24  (at step  50 ) is transferred to the controlling portion  26  through the communication controlling portion  27  of the optical disc drive  10 . The controlling portion  26  determines whether or not the transferred command is the valid first command that is issued just after the command generating unit  23  gets started. When the transferred command is not the first command, the controlling portion  26  performs a terminating process. 
     When the transferred command is the first command, the controlling portion  26  waits for the next input. (steps  70  to  72 ) 
     While the controlling portion  26  is waiting for the next input, if the controlling portion  26  receives the next command from the host computer  21 , the controlling portion  26  determines that the first command is a command that is not issued by the user. (step  73 ) 
     While the controlling portion  26  is waiting for the next input, if the controlling portion  26  detects an operation signal corresponding to the user&#39;s operation of the ejection switch  31 , the controlling portion  26  sets count value “1” to the operation detecting/counter portion  30  that stores data that represents the number of times of the operation of the ejection switch  31 . (step  74 ) 
     Thereafter, the controlling portion  26  sets an operation waiting time period for detecting each operation of the ejection switch  31  that is successively pressed. (step  75 ) 
     When the user operates the ejection switch  31  in the operation waiting time period, the controlling portion  26  determines that the ejection switch  31  has been operated again and increments the count value of the operation detecting/counter portion  30  by “1”. (steps  76  to  80 ) 
     Thereafter, the flow returns to step  75 . The controlling portion  26  sets an operation waiting time period at step  75  and repeats the process. 
     When the operation of the ejection switch  31  has not been detected in the operation waiting time period at step  78 , the controlling portion  26  detects the current count value of the operation detecting/counter portion  30 . The controlling portion  26  decides the next process corresponding to the detected counter value. In this example, the controlling portion  26  performs different processes depending on whether the ejection switch  31  has been operated more than two times. When the ejection switch  31  has been successively operated twice or more, the controlling portion  26  sends data that represents this situation to the host computer  21 . In addition, the controlling portion  26  sets a waiting time period for the next command received from the host computer  21  and waits for the next command. (steps  81  and  82 ) 
     As shown in FIG. 4, the number of times that the user operates the ejection switch  31  is five in this embodiment. 
     When the host computer  21  receives such data from the controlling portion  26  of the optical disc drive  10 , as shown in FIG. 6, the host computer  21  displays a message on the screen that prompts the user to input for the number of times that user has pressed the ejection button  12 . The host computer  21  waits for the user&#39;s input. (step  52 ) 
     When the user inputs a value corresponding to the number of times that he or she has pressed the ejection button  12 , the command generating unit  23  of the host computer  21  generates the value as a second command. (step  53 ) 
     The second command is not a functional command, rather value data that is just sent to the optical disc drive  10 . 
     As described above, in this example, it is assumed that the user has operated the ejection switch  31  five times. Thus, the user inputs value “5” against the prompt to the host computer  21  with the keyboard or the like. 
     The command generating unit  23  transfers the generated second command to the OS  24 . (step  54 ) 
     The OS  24  further transfers the second command to the optical disc drive  10 . 
     As shown in FIG. 7, the controlling portion  26  of the optical disc drive  10  that is waiting for the next command receives the second command from the OS  24 . When the controlling portion  26  has received the second command within the predetermined command waiting time period, the controlling portion  26  activates the command validity determining portion  29 . The command validity determining portion  29  compares the count value of the operation detecting/counter portion  30  with the value of the second command. (steps  83  to  85 ) 
     When the count value matches the value of the second command, the command validity determining portion  29  determines that the first command is a valid command and transfers the first command to the command executing portion  28 . Thus, the command executing portion  28  executes the first command. (step  86 ) 
     Last, as shown in FIG. 5, the command generating unit  23  displays a message representing that the drive has been set on the screen and complete the process. (step  55 ) 
     (2) Second Embodiment 
     Next, with reference to FIGS. 8 to  11 , a second embodiment of the present invention will be described. 
     FIG. 8 is a state transition diagram showing a command transfer process of an optical disc drive according to a second embodiment of the present invention. FIG. 9 is a flow chart showing an operation process of a command generating unit of a host computer according to the second embodiment of the present invention. FIG. 10 is a schematic diagram showing the content of an output screen according to the second embodiment of the present invention. FIG. 11 is a flow chart showing a command execution restricting process of a controlling portion of the optical disc drive according to the second embodiment of the present invention. In the second embodiment, it is determined whether or not to execute a first command that causes an optical disc drive  10  to start corresponding to a user&#39;s disc close operation for loading a disc to a disc carrier  11  (tray type or drawer type) and a user&#39;s acknowledgment operation performed after the optical disc drive  10  is initialized. 
     As shown in FIG. 8, when the user changes the setting of the optical disc drive  10 , before the command generating unit  23  gets started (namely, before the user inputs a command “Reset drv” to a host computer  21  with an inputting unit (for example, a keyboard)), the disc carrier  11  should be opened. To do that, the user presses an ejection button  12  of the optical disc drive  10 . Alternatively, the host computer  21  issues an ejection command to the optical disc drive  10 . 
     Next, the user inputs a start command (for example, a command “Reset drv” shown in FIG. 10) that causes the command generating unit  23  to start to the host computer  21  with the inputting unit (for example, the keyboard). The start command that is input by the user is sent to the OS  24 . The OS  24  activates the command generating unit corresponding to the start command. 
     As shown in FIG. 9, when the command generating unit  23  gets started, it sends the first command to the OS  24 . (step  90 ) 
     The first command is issued just after the command generating unit  23  gets started. For example, the first command causes the optical disc drive  10  to start. 
     In addition, as shown in FIG. 10, the command generating unit  23  displays for example a message “PLACE ANY DISC ON THE TRAY AND CLOSE THE TRAY” that prompts the user to perform a predetermined operation on an outputting unit (for example, a display). (step  91 ) 
     As shown in FIG. 11, the first command that is sent to the OS  24  at step  90  is transferred to a controlling portion  26  through a communication controlling portion  27  of the optical disc drive  10 . (step  110 ) 
     The controlling portion  26  determines whether or not the transferred command is the valid first command that is issued just after the command generating portion  23  gets started. (step  111 ) 
     When the transferred command is not the valid first command, the controlling portion  26  performs a terminating process. 
     On the other hand, when the transferred command is the first command, the controlling portion  26  determines whether or not the disc carrier  11  is close. (step  112 ) 
     When the disc carrier  11  is close, the controlling portion  26  performs a terminating process. 
     When the disc carrier  11  is open, the controlling portion  26  sets a waiting time period. (step  113 ) 
     The waiting time period is the minimum time period for which the controlling portion  26  should wait for executing the first command. 
     After the waiting time period has elapsed, the controlling portion  26  waits for a signal that represents that the disc carrier  11  is close (hereinafter, this signal is referred to as tray close signal). When the controlling portion  26  receives the tray close signal, the controlling portion  26  starts initializing the optical disc drive  10 . (steps  114  to  117 ) 
     While the controlling portion  26  is initializing the optical disc drive  10 , an LED  13  blinks. After the controlling portion  26  has initialized the optical disc drive  10 , the LED  13  puts off. While the controlling portion  26  is initializing the optical disc drive  10 , if the controlling portion  26  receives the next command from the OS  24  of the host computer  21 , the controlling portion  26  determines that the command has not been issued by the user and performs a terminating process. (step  118 ) 
     The tray close signal is detected by the following mechanism. FIGS. 16 and 17 are schematic diagrams showing examples of tray close signal detecting mechanisms. In the example shown in FIG. 16, the tray close detecting mechanism does not have a motor that loads and unload the disc carrier  202 . The tray close detecting mechanism has a detecting switch  203  disposed at an inner position of a cabinet  201 . The detecting switch  203  is composed of for example a transmission type of an optical sensor. When the disc carrier  202  is loaded to the cabinet  201 , light emitted to the optical sensor is blocked by the disc carrier  202 . Thus, the level of an output signal of the detecting switch  203  varies. The controlling portion of the optical disc drive recognizes the variation of the level of the output signal of the detecting switch  203  so as to detect the tray close signal. 
     In the example shown in FIG. 17, the tray close detecting mechanism has a motor that loads and unloads the disc carrier. The tray close detecting mechanism has detecting switches  303  and  304 . The detecting switch  303  is disposed at an inner position of the cabinet  301 . The detecting switch  304  is disposed at an entrance of the cabinet  301 . The detecting switches  303  and  304  are composed of for example a transmission type of optical sensors. When the disc carrier  302  is loaded to and unloaded from the cabinet  301 , light emitted to the optical sensors is blocked by the disc carrier  302 . Thus, the levels of output signals of the detecting switches  303  and  304  are inverted. When the variations of the levels of the output signals of the detecting switches  303  and  304  satisfy predetermined conditions, the controlling portion of the optical disc drive detects the tray close signal. 
     After the optical disc drive  10  has been initialized, as shown in FIG. 10, the OS  24  of the host computer  21  displays a message on the screen that prompts the user to press the ENTER key. After the OS  24  has displayed the message, the OS waits for a user&#39;s input of the ENTER KEY. (step  92 ) 
     After the LED  13  puts off, the user knows that the optical disc drive  10  has been initialized and then presses the ENTER key with the inputting unit  25  (for example, the keyboard). Thus, the command generating unit  23  issues a second command corresponding to the input of the ENTER key to the OS  24  of the host computer  21 . (step  93 ) 
     The second command is just a command that causes the input of the ENTER key to be transferred to the OS  24  of the host computer  21 . 
     On the other hand, after the optical disc drive  10  has been initialized, the controlling portion  26  of the optical disc drive  10  determines whether or not a disc has been placed on the disc carrier  11 . (step  119 ) 
     When a disc has not been placed on the disc carrier  11 , the controlling portion  26  performs a terminating process. When a disc has been placed on the disc carrier  11 , the controlling portion  26  sets a predetermined transfer waiting time period. (step  120 ) 
     When the controlling portion  26  receives the next command from the OS  24  of the host computer  21  in the transfer waiting time period, the controlling portion  26  determines whether or not the received command is the second command representing that the user has pressed the ENTER key. (steps  121  to  123 ) 
     When the received command is not the second command, the controlling portion  26  cancels the received command as a command that has not been issued by the user and performs a terminating process. When the received command is the second command, the command executing portion  28  executes the first command. (step  124 ) 
     In addition, the controlling portion  26  displays a message representing that the optical disc drive  10  has been set. (step  94 ) 
     (3) Third Embodiment 
     Next, with reference to FIGS. 12 to  15 , a third embodiment of the present invention will be described. 
     FIG. 12 is a flow chart showing an operation process of a command generating unit of a host computer according to a third embodiment of the present invention. FIG. 13 is a schematic diagram showing the content of an output screen according to the third embodiment of the present invention. FIG. 14 is a flow chart showing a command execution restricting process of a controlling portion of the optical disc drive according to the third embodiment of the present invention. FIG. 15 is a schematic diagram showing an example of disc type information of the optical disc drive according to the third embodiment of the present invention. 
     As shown in FIG. 8, when the user changes the settings of the optical disc drive  10 , before the command generating unit  23  gets started (namely, before the user inputs a command “Reset drv” with an inputting unit  25  (for example, a keyboard)), a disc carrier  11  should be opened. 
     Next, the user inputs a start command (for example, a command “Reset drv” shown in FIG. 10) that causes the command generating unit  23  to start to the host computer  21  with the inputting unit (for example, the keyboard). The start command that is input by the user is sent to the OS  24 . The OS  24  activates the command generating unit corresponding to the start command. 
     As shown in FIG. 12, when the command generating unit  23  gets started, it sends the first command to the OS  24 . (step  130 ) 
     The first command is issued just after the command generating unit  23  gets started. For example, the first command causes the optical disc drive to start. 
     In addition, as shown in FIG. 13, the command generating unit  23  displays for example a message “PLACE ANY DISC ON THE TRAY AND CLOSE THE TRAY” that prompts the user to perform a predetermined operation on an outputting unit (for example, a display). (step  131 ) 
     As shown in FIG. 14, the first command that is sent to the OS  24  at step  130  is transferred to a controlling portion  26  through a communication controlling portion  27  of the optical disc drive  10 . (step  140 ) 
     The controlling portion  26  determines whether or not the transferred command is the valid first command that is issued just after the command generating portion  23  gets started. (step  141 ) 
     When the transferred command is not the valid first command, the controlling portion  26  performs a terminating process. 
     On the other hand, when the transferred command is the first command, the controlling portion  26  determines whether or not the disc carrier  11  is close. (step  142 ) 
     When the disc carrier  11  is close, the controlling portion  26  performs a terminating process. 
     When the disc carrier  11  is open, the controlling portion  26  sets a waiting time period. (step  143 ) 
     The waiting time period is the minimum time period for which the controlling portion  26  should wait for executing the first command. 
     After the waiting time period has elapsed, the controlling portion  26  waits for a signal that represents that the disc carrier  11  is close (hereinafter, this signal is referred to as tray close signal). When the controlling portion  26  receives the tray close signal, the controlling portion  26  starts initializing the optical disc drive  10 . (steps  144  to  146 ) 
     While the controlling portion  26  is initializing the optical disc drive  10 , an LED  13  blinks. After the controlling portion  26  has initialized the optical disc drive  10 , the LED  13  puts off. While the controlling portion  26  is initializing the optical disc drive  10 , if the controlling portion  26  receives the next command from the OS  24  of the host computer  21 , the controlling portion  26  determines that the command has not been issued by the user and performs a terminating process. 
     The tray close signal has the same mechanism that it is described in the second embodiment. 
     When the controlling portion  26  receives the next command from the OS  24  of the host computer  21  while the controlling portion  26  is initializing the optical disc drive  10 , the controlling portion  26  treats the received command as a command that has not been issued by the user and performs a terminating process. After the controlling portion  26  has initialized the optical disc drive  10 , the controlling portion  26  determines whether or not a disc has been placed on the disc carrier  11 . (step  147  and step  148 ) 
     When a disc has not been placed on the disc carrier  11 , the controlling portion  26  performs a terminating process. When a disc has been placed on the disc carrier  11 , the controlling portion  26  extracts disc type information from the disc. (step  149 ) 
     As shown in FIG. 15, a disc  160  has a lead-in area that contains disc management information. The lead-in area  161  is disposed on an innermost periphery  160   a  of the disc  160 . The lead-in area  161  has a Q mode area  162  that contains information of each track of the disc. The Q mode area  162  contains a control area bit portion  163 , a track signal  164 , a start address  165 , and so forth. The disc type information is contained in the control area bit portion  163 . 
     On the other hand, after the optical disc drive  10  has been initialized, as shown in FIG. 13, the user selects a disc type number of the disc placed on the disc carrier  11  from a disc type list displayed on the screen with the inputting unit  25  (for example, the keyboard). After the optical disc drive  10  has been initialized, the command generating unit  23  waits for a user&#39;s input of the disc type number. (step  132 ) 
     When the controlling portion  26  has received the disc type number, the controlling portion  26  generates a second command corresponding to the input disc type number. The second command is transferred to the optical disc drive  10  through the OS  24 . (step  133 ) 
     After the controlling portion  26  of the optical disc drive  10  has extracted the disc type information from the disc, the controlling portion  26  sets a predetermined transfer waiting time period. (step  150 ) 
     When the controlling portion  26  receives the next command from the OS  24  of the host computer  21  in the transfer waiting time period, the controlling portion  26  determines whether or not the received command is a second command that represents the disc type selected by the user. (steps  151  to  153 ) 
     When the received command is not the second command, the controlling portion  26  cancels the received command as a command that has not been issued by the user and performs a terminating process. On the other hand, when the received command is the second command, the command validity determining portion  29  compares the disc type information obtained from the disc with the disc type information represented by the second command. (step  154 ) 
     When the disc type information of the disc matches the disc type information of the second command, the command validity determining portion  29  determines that the first command is a valid command. The command executing portion  28  executes the first command. (step  155 ) 
     After the command executing portion  28  has executed the first command, the command generating unit  23  displays a message that represents that the optical disc drive has been set on the screen as shown in FIG.  13  and performs a terminating process. (step  134 ) 
     As described above, according to the above-described embodiments, since the optical disc drive determines whether or not a command received from the host computer is valid corresponding to information that is generated by the operation of the ejection button, the tray close operation, the operation of the ENTER key of the keyboard, or the disc type selection operation that can be performed by only the true user. Thus, the optical disc drive can be prevented from executing a virus-infected command that has not been issued by the user. 
     The present invention is not limited to the above-described embodiments. In other words, in the scope and spirit of the present invention, various modifications and changes are available. 
     In the above-described embodiments, an optical disc drive was explained. However, the function according to the present invention can be applied to an optical disc drive in such a manner that a program stored in a program record medium such as a floppy disk or a CD-ROM is installed to a system. 
     In addition, a program that accomplishes the function according to the present invention can be downloaded through a communication line. 
     The function according to the present invention may be supplied to an optical disc drive with a program stored in a semiconductor memory such as a flash ROM or an EEPROM (Electrically Erasable Programmable Read Only Memory). 
     In the first embodiment, when the count value of which the ejection switch  31  has been successively pressed in the predetermined time period matches the value of the second command transferred from the host computer  21 , the first command is executed. Alternatively, a command that represents the end of the operation of the ejection switch  31  may be used as the second command. In this case, after the count value of which the ejection switch has been successively pressed in a predetermined time period is detected until the command is transferred, when the count value matches the predetermined value, the first command is executed. 
     The waiting time period may be a time period after the ejection switch is pressed until the disc stops and the tray with the disc is fully unloaded. 
     The waiting time period after the transfer time of the first command until the end of the operation can be freely selected by the user. The waiting time period defines the end time of the entire operation of the optical disc drive. Thus, a computer virus cannot imitate the second command transferred to the optical disc drive. Likewise, the transfer waiting time period can be freely selected by the user. Even if a computer virus performs a particular operation in the waiting time period, it is very difficult to imitate the second command in the transfer waiting time period. 
     The ejecting operation of the ejection switch used in the command execution restricting method of the disc reproducing apparatus according to the present invention does not relate to the normal ejecting operation of the apparatus. 
     FIGS. 16 and 17 are conceptual diagrams showing the disc carriers in the case that the ejection switch is pressed. 
     As shown in FIGS. 16 and 17, the close switches detect whether or not the tray/drawer is closed. 
     The normal ejecting state means a state that a part or all of a disc or a cassette that surrounds the disc protrudes from the disc reproducing apparatus. 
     Although the present invention has been shown and described with respect to a best mode embodiment thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions, and additions in the form and detail thereof may be made therein without departing from the spirit and scope of the present invention.