the above objects , other objects , features and advantages of the present invention will be better understood from the following description taken in conjunction with the attached drawings . fig4 is a block diagram showing a basic configuration of a television having a real time channel grouping function according to the first embodiment of the present invention . as shown , the television 100 having a real time channel grouping function comprises an input unit 110 , a remote controller 115 , a tuner unit 120 , a signal processing unit 140 , a controlling unit 170 , gui screen 160 , and a screen display unit 180 . the input unit 110 is provided on the body of the television and comprises a plurality of operation keys , including for example keys such as a channel group key , a group display key ( not shown ) for performing various operations . that is , the user &# 39 ; s selection commands such as channel selection and volume adjustment are inputted by the plurality of operation keys of the input unit 110 . additionally , the user may input the selection commands using the remote controller 115 provided with the plurality of operation keys . the tuner unit 120 selects the channel selected by the user and carries out the function of outputting a selected channel to the signal processing unit 140 , after the television receives an on signal . the signal processing unit 140 processes a signal inputted from the tuner unit 120 and allows the processed signal to be displayed on the screen display unit 180 . the screen display unit 180 may be comprised of a general display device . it will be understood that the display device may be a crt display , a flat - screen apparatus , such as an lcd or plasma display , a rear or front projection display apparatus , or any other type of device capable of displaying audio - visual information , whether or not physically attached or connected to the television set or logically connected to the television . the gui screen storage unit 171 stores the gui screen and performs the function of transferring the gui screen to the signal processing unit 140 under the control of the controlling unit 170 . the controlling unit 170 controls the tuner unit 120 to select channels in response to the selection command of the user , and when the “ channel group key ” and “ channel display key ” associated with the present invention are inputted via the input unit 110 by the user , the controlling unit 170 fetches the necessary screen from the gui screen storage unit 171 and allows the fetched screen to be displayed on the screen display unit 180 . hereinafter , an operation of real time channel grouping according to a first embodiment of the present invention will be described with reference to fig4 , 7 a , 7 b , and 12 . fig7 a is a view showing a group selection screen using gui information displayed on the broadcasting that is received , fig7 b is a view of gui screen that is displayed for storing a selected channel in a group , and fig1 is a flow chart explaining operations for grouping channels in real time according to the first embodiment of the present invention . as shown , when the user inputs the “ channel group key ” via the remote controller 115 and the input unit 110 for grouping a preference channel into a specific group while watching the broadcasting 600 through the screen display unit 180 ( step s 110 ), the controlling unit 170 allows gui screen 610 for selecting the group as shown in fig7 a from the gui screen storage unit 171 to be displayed on the screen display unit 180 . additionally , the controlling unit 170 controls the tuner unit 120 to allow the channels included in preset group , “ group 1 ”, to be sequentially displayed for a certain period ( step s 120 ). for example , in the present embodiment , there are three selectable groups . the user selects and stores group 2 ; channels 5 , 6 , and 7 are set in “ group 1 ,” and channels 1 , 2 , and 3 are stored in “ group 2 .” additionally , in the initial group selection screen display , a selection bar 620 is displayed on the preset group , “ group 1 ” and a desired group may be selected by shifting the selection window 620 using left and right selection keys ( not shown ). accordingly , the channels 5 , 6 , and 7 being set in the preset group are supposed to be sequentially displayed on the screen display unit 180 until the user selects the group . if the user does not select the group , the process iteratively performs the procedures beginning with the step s 120 . if the user selects “ group 2 ” using the left and right selection keys ( not shown ) ( the step s 130 ), the controlling unit 170 displays another gui screen 630 determining whether the channel displayed for the selected group as shown in fig7 b is stored , and sequentially displays the channels corresponding to the selected “ group 2 ” for a certain period ( the step s 140 ). if the user wishes to store the received channel in the selected group ( the step s 150 ), the controlling unit 170 stores the channel that is received in the selection group ( group 2 ), performs the off operation of its associated gui screen 610 ( the step s 160 ), and thereby the process ends . in the step s 150 , if the user wishes not to store the received channel in the selected group , the process iteratively performs the step s 140 . if no “ channel group key ” is inputted in the step s 110 , the process ends . additionally , in a preferred embodiment , a “ save ” “ soft - button ” indicating storage is displayed , and “ cancel ” “ soft - button ” indicating cancellation of the gui screen 630 , so that the user can select and control the process . in a preferred embodiment , in the initial display , the selection bar 620 is displayed corresponding to “ save ” ( indicating storage as the option ). hereinafter , in the case where the user establishes each group by iteratively performing the operations above , the description will be made of a method in which the channels stored in the each group are displayed on the screen . fig1 is a view showing a group display screen using gui shown on the broadcasting that is received , fig1 a is a view sequentially showing channels belonging to a selected group , and fig1 is a flow chart showing procedures for selecting channels using a group display key by a user . as shown , if the user inputs the “ group display key ” of the remote controller 115 or the input unit 110 while watching the broadcasting 600 through the screen display unit 180 ( step s 210 ), the controlling unit 170 allows gui screen 610 for selecting the group stored in the gui screen storage unit 171 to be displayed on the screen display unit 180 . additionally , the controlling unit 170 controls the tuner unit 120 for allowing the channel included in preset group , “ group 1 ”, to be sequentially displayed for a certain period . if the user does not select the group , the process iteratively performs the step s 220 . if the user selects the group , for example using the left and right selection keys ( not shown ) of the remote controller 115 or the input unit 110 ( the step s 230 ), the controlling unit 170 controls the tuner unit 120 to enable the channels being set in the selected group of preference channels to be sequentially displayed ( step s 240 ). for example , in the present embodiment , a case in which three groups are selectable , a selection window 620 is displayed for the preset group , “ group 1 ,” in the initial group selection screen display , and the user in this instance selects group 2 using the left and right selection keys ( not shown ). as shown in fig1 a , if the user selects “ group 2 ”, the controlling unit 170 controls the tuner unit 120 so that initially “ channel 1 ” is received for a certain period , then “ channel 2 ” is received for the certain period , and then the final channel , “ channel 3 ” is received for the certain period again in series , and the process iteratively performs the operations above until the user selects a specific channel . additionally , if the channels are received in series as shown in fig1 a , in order to inform the user of the information that the channel belonging to the group , “ group 2 ”, selected by the user , is being displayed , in a preferred embodiment the group number information is displayed using gui screen 640 . if the user does not select a specific channel during the sequential display of the channels , the process iteratively performs the step s 240 . if the user does select a specific channel ( yes at the step s 250 ), the controlling unit 170 stops the sequential display of the channels and controls the tuner unit 120 and the signal processing unit 140 so that the selected channel can be received ( the step s 260 ), and thereby the process ends . additionally , the controlling unit 170 performs the off processing for the gui screen 640 being displayed . thus , if no is selected at the “ group display key ” in step s 210 , the process ends . hereinafter , the second embodiment for achieving the object of the present invention will be described . fig5 is a block diagram showing the configuration of real time channel grouping television having one pip function according to the second embodiment of the present invention . as shown , the television 200 comprises an input unit 210 , a tuner unit 220 , a switching unit 230 , a main screen unit 240 , a sub - screen unit 250 , a synthesizer 260 , a controlling unit 270 , gui screen storage unit 271 , and a screen display unit 280 . since the configurations of the gui screen storage unit 271 and the screen display unit 280 of the present embodiment are identical to those of the gui screen storage unit 171 and the screen display unit 180 of the first embodiment , the explanation on thereof will be omitted . the input unit 210 is provided on the body of the television and comprises a plurality of operation keys , including for example channel group key , group display key , and the like ( not shown ), for performing various operations of the television . in particular , the user &# 39 ; s selection commands such as channel selection , pip function , and volume adjustment are inputted through the plurality of operation keys of the input unit 210 . generally , the user may input the selection commands using the remote controller 215 provided with the plurality of operation keys . the tuner unit 220 includes a main tuner unit 222 and a sub - tuner unit 224 . generally , when the television receives an on signal , the main tuner unit 222 selects the channel that is preset or selected by the user . when the pip function is executed , the sub - tuner unit 224 selects a corresponding sub - screen channel under the control of the controlling unit 270 . when the user executes the pip function by selecting the pip function key provided on the input unit 210 and the remote controller 215 , the switching unit 230 switches the signal for the channel selected by the main tuner unit 222 and the sub - tuner unit 224 to provide the switched signal to the main screen unit 240 and the sub - screen unit 250 . the main screen unit 240 processes image signal of the broadcasting signals of the channel selected by the main tuner unit 222 so that the image signal is suitable to the main screen size , and outputs the processed signal as a main screen signal . additionally , the sub - screen unit 250 processes the image signal of the broadcasting signals of the channel selected by the sub - tuner unit 224 so that the image signal is suitable to the sub - screen size , and outputs the processed signal as a sub - screen signal . in addition , if the “ channel group key ” or “ group display key ” is activated , the sub - screen unit 250 receives the sub - screen image signal for a certain period and outputs the same so that the channels belonging to the selected group are sequentially displayed on the sub - screen . the synthesizer 260 synthesizes the image signal of the main screen and the image signal of the sub - screen so that the main screen and the sub - screen can be displayed by the screen display unit 280 , to output the synthesized image signal . that is , the synthesizer 260 is to cause the main screen and the sub - screen to be displayed , the sub - screen being displayed on a predetermined region of the main screen . the controlling unit 270 controls the tuner unit 220 to select the channel in response to the selection commands of the user . in other words , when the “ channel group key ” or “ channel display key ” is inputted via the input unit 210 by the user , the controlling unit 270 fetches the necessary gui screen from the gui screen storage unit 271 and controls the synthesizer 260 to display the gui screen on the screen display unit 280 . additionally , the controlling unit 270 controls the main tuner unit 222 so that the broadcasting that is received can be displayed as a main screen by executing the on operation of pip screen , and controls the sub - tuner unit 224 so that the channels of the selected group can be sequentially received in the sub - screen for a certain period . hereinafter , the operation of real time channel grouping according to the second embodiment of the present invention will be described with reference to fig5 , 8 a , 8 b , and 14 fig8 a is a view showing pip screen 710 and group selection screen 730 using gui in the broadcasting that is received , fig8 b is a view of gui screen 740 that is displayed for storing a selected channel in a group , and fig1 is a flow chart explaining the operations for grouping channels in real time according to the second embodiment of the present invention . as shown , when the user inputs the “ channel group key ” of the remote controller 215 and the input unit 210 for grouping his preference channel into a specific group while watching the broadcasting 700 using the main tuner unit 222 ( the step s 610 ), the controlling unit 270 allows gui screen 730 for selecting a group as shown in fig8 a from the gui screen storage unit 271 to be displayed on a predetermined region of the screen display unit 280 superposed on the channel that is received . at the same time , the controlling unit 270 executes the on operation of the pip function and controls the sub - tuner unit 224 to allow the channels included in a preset group , “ group 1 ”, to be sequentially displayed on the sub - screen 710 for a certain period ( the step s 620 ). that is , the controlling unit 270 causes the channels 5 , 6 , and 7 stored in “ group 1 ” to be sequentially displayed . additionally , even when the user has been watching the pip screen , when the “ channel group key ” is inputted , it is desirable to perform the same operation . for example , in the present embodiment , when three groups are selectable , the user may select group 2 , with channels 1 , 2 , and 3 set in “ group 2 ”. additionally , in the initial group selection screen display , a selection bar 720 is displayed on the preset group , “ group 1 ” and a desired group may be selected using the left and right selection keys ( not shown ). accordingly , the “ channel 5 ” being stored in “ group 1 ” is displayed on the sub - screen 710 first until the user selects the group ( see fig8 a ). if the user does not select a group , the process iteratively performs the procedures of the step s 620 . if the user selects “ group 2 ” using the left and right selection keys ( not shown ) ( the step s 630 ), the controlling unit 270 displays another gui screen 740 inquiring whether the channel that is currently received on the main screen is to be stored in group 2 , while sequentially displaying the channels of the selected group as shown in fig8 b on the sub - screen 730 for a certain period ( channels 1 , 2 , and 3 being sequentially and iteratively displayed ) ( the step s 640 ). if the user wishes to store the received main channel in the selected group using the selection window 720 ( the step s 650 ), the controlling unit 270 stores the main channel that is received in the selection group ( group 2 ) and performs the off operation of the associated gui screen 740 and pip screen ( the step s 660 ), and thereby the process ends . in the step s 650 , if the user does not wish to store the received channel in the selected group , the process iteratively performs the step s 640 . if the “ channel group key ” is not inputted in the step s 610 , the process ends . hereinafter , in the case where the user establishes each group by iteratively performing the operations above , the description will be made of displaying the channels stored in each group on the screen . fig1 b is a view showing a gui group display screen transposed on the broadcasting that is received , and fig1 is a flow chart showing procedures for selecting the preference channels using the “ group display key ”. as shown , if the user inputs the “ group display key ” of the remote controller 215 or the input unit 210 for grouping the preference channel into a specific group while watching the broadcasting 700 through the screen display unit 280 ( the step s 310 ), the controlling unit 270 allows the screen ( fig8 a ) for selecting a group stored in the gui screen storage unit 271 to be displayed on the screen display unit 280 . additionally , the controlling unit 270 performs the on operation of the pip screen and concurrently allows “ channel 1 ” included in preset group ( in the present embodiment , “ group 1 ”) to be displayed on the sub - screen 710 ( the step s 320 ). if the user does not selects the group to be watched , the process iteratively performs the step s 320 . if the user selects the group using the left and right selection keys ( not shown ) of the remote controller 215 or the input unit 210 ( the step s 330 ), as shown in fig1 b , the controlling unit 270 controls the sub - tuner unit 224 to allow the channels being set in the selected group to be sequentially displayed on the sub - screen 710 and to allow gui screen 750 indicating that the channel that is currently selected is group 2 to be displayed on the screen display unit 280 ( the step s 340 ). for example , in the present embodiment , in the case in which there are three groups selectable , a selection window 750 is displayed for the preset group , “ group 1 ,” in the initial group selection screen display , and the user may select group 2 , for example using left and right selection keys ( not shown ). additionally , in the present embodiment , for example , assume that the channels 1 , 2 , and 3 , i . e ., three channels , are set in “ group 2 ”. as shown in fig1 b , the user selects “ group 2 ”, the controlling unit 270 controls the tuner unit 220 so that initially “ channel 1 ” is received for a certain period , “ channel 2 ” is received since the certain period , and finally channel 3 is received for the certain period in series . the above - described process is iteratively performed until the user selects a specific channel . if the user does not select a specific channel during the sequential display of the channels on the sub - screen 710 , the process iteratively performs the step s 340 . if the user selects the specific channel ( the step s 350 ), the controlling unit 270 stops the sequential display of the channels and performs the off operation of pip screen and gui screen so that the selected channel can be displayed on the main screen ( the step s 360 ), thereby the process ends . then , if the “ group display key ” in step s 310 is not selected , the process ends . hereinafter , the third embodiment for achieving the object of the present invention will be described . fig6 is a block diagram showing the basic configuration of television having multi - pip function according to the third embodiment of the present invention . as shown , the television 300 having the multi - pip function according to the present invention comprises an input unit 310 , a tuner unit 320 , a switching unit 330 , a first scaler 340 , a second scaler 350 , a third scaler 360 , a fourth scalar 365 , a first synthesizer 370 , a second synthesizer 380 , a third synthesizer 385 , a controlling unit 400 , gui screen storage unit 401 , and a screen display unit 390 . since the configurations of the gui screen storage unit 401 and the screen display unit 390 of the present embodiment are identical to those of the previous embodiments of the present invention , their detailed explanation will be omitted . the input unit 310 is provided on the body of the television and comprises a plurality of operation keys , including for example channel group key , group display key , and the like ( not shown ), for performing various operations of the television . that is , the user &# 39 ; s selection commands such as channel selection and volume adjustment are inputted through the plurality of operation keys of the input unit 310 . generally , the user may input the selection commands using the remote controller 315 provided with the plurality of operation keys from the remote location . in the television having the multi - pip function , it is a matter of course that the input unit 310 and the remote controller 315 are provided with a predetermined function key for the pip function and a function key for channel search . alternatively , separate function keys may be provided , instead of a plurality of keys provided with various other functions . the tuner unit 320 includes a main tuner unit 322 and at least three sub - tuner units 324 , 326 , and 328 . generally , when an on signal is transmitted , the main tuner unit 322 selects the channel that is preset . additionally , when the television is inputted with the channel selection command to be implemented in the main screen by the user , the main tuner unit 322 selects the channel corresponding to the command . when the pip function is executed , the sub - tuner units 324 , 326 , and 328 select a corresponding channel under the control of the controlling unit 400 . the number of the sub - tuner units 324 , 326 , and 328 may be n , wherein n is defined as a positive integer . for example , in order to receive four different rf broadcasting signals and to implement the signals on the screen , one main tuner unit 322 and at least three sub - tuner units 324 , 326 , and 328 should be provided . for example , in the present embodiment , a case in which one main tuner unit 322 and at least three sub - tuner units 324 , 326 , and 328 are provided to select different image signals is considered . the image signal of the channel selected by the main tuner unit 322 is outputted as a first image signal ( signal_ 1 ), the image signal of the channel selected by the first sub - tuner unit 324 is outputted as a second image signal ( signal_ 2 ), the image signal of the channel selected by the second sub - tuner unit 326 is outputted as a third image signal ( signal_ 3 ), and the image signal of the channel selected by the third sub - tuner unit 328 is outputted as a fourth image signal ( signal_ 4 ). when the user executes the pip function by selecting the multi - pip function key provided on the input unit 310 and the remote controller 315 , the switching unit 330 switches the first image signal ( signal_ 1 ), the second image signal ( signal_ 2 ), the third image signal ( signal_ 3 ), and the fourth image signal ( signal_ 4 ) for the channels selected by the main tuner unit 322 , the first sub - tuner unit 324 , the second sub - tuner unit 326 , and the third sub - tuner unit 328 to provide the switched signals to the first scaler 340 , the second scalar 350 , the third scaler 360 , and the fourth scaler 365 , respectively . in addition , if the user inputs the “ channel group key ” or “ group display key ”, the switching unit 330 allows the channel being set in the selected group to be received via each of the sub - tuner units . in response to the screen selection command , the switching unit 330 may selectively supply each of the first image signal ( signal_ 1 ), the second image signal ( signal_ 2 ), the third image signal ( signal_ 3 ), and the fourth image signal ( signal_ 4 ) to any of the first scaler 340 , the second scaler 350 , the third scaler 360 , and the fourth scaler 365 . additionally , the switching unit 330 may change , based on the user &# 39 ; s screen change command , the supply path of each of the first image signal ( signal_ 1 ), the second image signal ( signal_ 2 ), the third image signal ( signal_ 3 ), and the fourth image signal ( signal_ 4 ) that is supplied to the first scaler 340 , the second scaler 350 , the third scaler 360 , and the fourth scaler 365 , respectively . specifically , when the user &# 39 ; s screen change command is inputted , the switching unit 330 supplies the first image signal ( signal_ 1 ) that is inputted to the first scaler 340 to the second scaler 350 , the second image signal ( signal_ 2 ) that is inputted to the second scaler 350 to the third scaler 360 , the third image signal ( signal_ 3 ) that is inputted to the third scaler 360 to the fourth scaler 365 , and the fourth image signal ( signal_ 4 ) that is inputted to the fourth scaler 365 to the first scaler 340 . in other words , the image that is implemented in a first main screen 600 , a first sub - screen 860 , a second sub - screen 850 , and a third sub - screen 840 may be changed within a plurality of image signals ( signal_ 1 , signal_ 2 , signal_ 3 ) that are inputted by the user &# 39 ; s screen change command . the first scaler 340 scales the first image signal ( signal_ 1 ) of the channel selected by the main tuner unit 322 to conform in size to the first main screen and outputs the scaled first image signal . the second scaler 350 scales the second image signal ( signal_ 2 ) of the channel selected by the first sub - tuner unit 324 to conform in size to the first sub - screen and outputs the scaled second image signal . the first synthesizer 370 synthesizes the first main screen and the first sub - screen so that the first main screen and the first sub - screen can be displayed on the screen display unit 390 , thereby generating a first screen 371 . the third image signal ( signal_ 3 ) from the switching unit 330 to the third scaler 360 is scaled to conform in size to the second sub - screen in the third scaler 360 . that is , the third scaler 360 scales the third image signal ( signal_ 3 ) of the channel selected by the second sub - tuner unit 324 to conform in size to the second sub - screen and outputs the scaled third image signal . the second synthesizer 380 synthesizes the first screen output at 371 and the second sub - screen that is outputted from the third scaler 360 , thereby generating a second screen output at 372 . the second screen is comprised of the first screen and the second sub - screen , and in turn the first screen is comprised of the first main screen and the first sub - screen . that is , the second screen is comprised of one main screen and two sub - screens . at this time , the first screen 371 operates like the main screen , and the second sub - screen operates like the sub - screen . the fourth image signal ( signal_ 4 ) from the switching unit 330 to the fourth scaler 365 is scaled to conform to the third sub - screen size in the fourth scaler 365 . the third synthesizer 385 synthesizes the second screen and the third sub - screen , thereby generating a third screen output at 373 . the third screen is comprised of the second screen and the third sub - screen , and the second screen in turn is comprised of the first screen and the second sub - screen . that is , the third screen is comprised of one main screen and three sub - screens . at this time , the second screen 372 operates like the main screen , and the third sub - screen operates like the sub - screen . according to a preferred embodiment , each of the first scaler 340 , the second scaler 350 , the third scaler 360 , and the fourth scaler 365 performs the functions above as a part of an integrated chip . it will be understood however that more than one ic may be used to implement the relevant features of a system according to the present invention , and such a system may be implemented without the use of an ic . the screen display unit 390 allows the third screen to be displayed on a region of the main screen , and the third sub - screen to be displayed on a predetermined region of the main screen , thereby displaying the three sub - screens . hereinafter , the operation of real time channel grouping according to the third embodiment of the present invention will be described with reference to fig6 , 9 a , 9 b , and 16 . fig9 a is a view showing multi - pip screen and group selection screen gui transposed on the broadcasting that is received , fig9 b is a view of a gui screen that is displayed for storing a selected channel in a group , and fig1 is a flow chart explaining the operations for grouping channels in real time according to the third embodiment of the present invention . as shown , when the user inputs the “ channel group key ” of the remote controller 315 or the input unit 310 for storing a broadcasting 800 in a specific group while watching the broadcasting 800 using the main tuner unit 322 ( the step s 410 ), the controlling unit 400 allows gui screen 810 for selecting a group as shown in fig9 a from the gui screen storage unit 401 to be displayed on a predetermined region of the screen display unit 390 superposed on the channel that is received . at the same time , the controlling unit 400 executes the on operation of the multi - pip function and controls the first sub - tuner unit 324 , the second sub - tuner unit 326 , and the third sub - tuner unit 328 to allow the channels included in preset group , “ group 1 ”, to be displayed on the sub - screens 840 , 850 , and 860 , respectively ( the step s 420 ). for example , in the present embodiment , a case in which three groups are selectable , the user may select group 2 , the channels 5 , 6 , and 7 being set in “ group 1 ”, and channels 1 , 2 , and 3 being set in “ group 2 ” is considered . additionally , in the initial group selection screen display , a selection bar 820 is displayed on the preset group , “ group 1 ” and a desired group may be selected using the left and right selection keys ( not shown ). accordingly , “ the channel 5 ” being part of “ group 1 ” is displayed on the first sub - screen 840 , “ the channel 6 ” also part of “ group 1 ” is displayed on the second sub - screen 850 , and “ the channel 7 ” being part of “ group 1 ” is displayed on the third sub - screen 860 until the user selects a group ( see fig9 a ). if the user does not select a group , the process iteratively performs the procedures beginning with the step s 420 . if the user selects “ group 2 ” in which to store the channel ( the step s 430 ), the controlling unit 400 displays another gui screen 830 inquiring whether the channel that is currently received in the main screen is to be stored in group 2 , while displaying the channels stored in the selected group as shown in fig9 b , one channel on each sub - screen ( the step s 440 ). it is desirable to display “ save ” indicating storage , and “ cancel ” indicating cancellation of the gui screen 830 , so as to allow the user to select the one he wishes . if the user wishes to store the received channel in the selected group using the selection window 820 ( the step s 450 ), the controlling unit 400 stores the channel that has been received in the selection group ( group 2 ) and performs the off operations of its associated gui screen 830 and the multi - pip screen ( the step s 460 ), and thereby the process ends . at the step s 450 , if the user does not wish to store the received channel in the selected group , the process iteratively performs the step s 440 , and if “ the channel group key ” is not inputted in the step s 410 , the process ends . hereinafter , in case the user establishes each group by iteratively performing the operations above , description will be made of how the channels stored in the each group on the multi - pip screen are displayed . fig1 c is a multi - pip view showing a gui group display screen in the broadcasting that is received , and fig1 is a flow chart showing procedures for selecting the channels using the “ group display key ” by user . as shown , if the user inputs the “ group display key ” of the remote controller 315 or the input unit 310 while watching the broadcasting through the screen display unit 390 ( the step s 510 ), the controlling unit 400 allows the screen ( see fig9 a ) for selecting group stored in the gui screen storage unit 401 to be displayed on the screen display unit 390 . additionally , the controlling unit 400 performs the on operation of the multi - pip screen and concurrently allows the channels 1 , 2 and 3 included in preset group ( in the present embodiment , “ group 1 ”) to be displayed on each of the sub - screens 840 , 850 , and 860 ( the step s 520 ). if the user does not select a group to be watched , the process iteratively performs the step s 520 . if the user selects a group to be displayed using the left and right selection keys ( not shown ) of the remote controller 315 or the input unit 310 ( the step s 530 ), as shown in fig1 c , the controlling unit 400 controls the sub - tuner units 324 , 326 , and 328 to allow the channels being set in the selected group to be displayed on each of the sub - screens 840 , 850 , and 860 , and to allow gui screen 870 indicating the channel that is currently selected , group 2 , to be displayed on the screen display unit 390 ( the step s 540 ). if the user does not select the specific channel using the selection window 880 during the sequential display of the channels on the sub - screens 840 , 850 , and 860 , the process iteratively performs the step s 440 . if the user selects the specific channel ( the step s 550 ), the controlling unit 400 performs the off operations of pip screen and gui screen 870 while allowing the selected channel to be displayed on the main screen ( the step s 560 ), and thereby the process ends . then , if the “ group display key ” at step s 510 is not selected , the process ends . although technical aspects of the present invention have been disclosed with reference to the appended drawings , and the preferred embodiments of the present invention corresponding to the drawings have been described , descriptions in the present specification are only for illustrative purposes , not for limiting the present invention . also , those who are skilled in the art will appreciate that various combinations , modifications , additions and substitutions are possible without departing from the scope and spirit of the present invention . therefore , it should be understood that the present invention is limited only by the accompanying claims and the equivalents thereof , and includes the aforementioned combinations , modifications , additions and substitutions .