Patent Publication Number: US-2022236842-A1

Title: User terminal device and displaying method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of U.S. application Ser. No. 17/091,456, filed on Nov. 6, 2020, which is a Continuation Application of U.S. application Ser. No. 16/683,629, filed on Nov. 14, 2019, which was issued as U.S. Pat. No. 10,831,343 on Nov. 10, 2020 which is a Continuation Application of U.S. patent application Ser. No. 16/165,736, filed on Oct. 19, 2018, which was issued as U.S. Pat. No. 10,503,368 on Dec. 10, 2019, which is a Continuation Application of U.S. patent application Ser. No. 14/618,447, filed on Feb. 10, 2015, in the U.S. Patent and Trademark Office, which was issued as U.S. Pat. No. 10,152,201 on Dec. 11, 2018, which claims priority from Korean Patent Application No. 10-2014-0083244, filed in the Korean Intellectual Property Office on Jul. 3, 2014, and the benefit of U.S. Provisional Application No. 61/937,744, filed in the United States Patent and Trademark Office on Feb. 10, 2014, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with exemplary embodiments relate to a user terminal device and a displaying method thereof, and more particularly, to a user terminal device where a display is folded asymmetrically with reference to a folding line so as to expose a part of the display and a displaying method thereof. 
     2. Description of Related Art 
     With the development of electronic technology, various types of user terminal devices have been developed and distributed. Recently, the size of such user terminal devices has been minimized while the functions of the devices have become diverse and thus, the demands for user terminal devices have been increasing continuously. 
     A user terminal device may provide various content such as multimedia content and application screens according to a user&#39;s request. A user may select a desired function using a button or a touch screen provided with a user terminal device. A user terminal device may execute a program selectively according to a user interaction and display the result of execution. 
     Meanwhile, as a user terminal device provides far more diverse functions, there are various needs for a method of displaying content or a user interface method. In other words, as the method of displaying content has changed and the type and function of content have increased, the existing interaction methods, such as simply selecting a button or touching a screen, may not be sufficient to perform various functions of a user terminal device. 
     Particularly, a user terminal device of which display can be folded with reference to a folding line has been developed in order to minimize the size of the user terminal device. When the display is folded symmetrically with reference to the folding line, however, the display is folded completely and a user may not use or watch the display. 
     SUMMARY 
     Aspects of one or more exemplary embodiments relate to a user terminal device that, when a display is folded asymmetrically with reference to a folding line, exposes a part of the display, provides various User Interface (UI) through the exposed area, and a displaying method thereof. 
     According to an aspect of an exemplary embodiment, there is provided a displaying method of a user terminal device including a display which is divided into a first area and a second area by a folding line, the second area being larger than the first area and including an exposure area that is exposed while the display is folded along the folding line such that the first area faces the second area, the method including displaying a first screen on the first area and the second area, detecting at least one of a first folding interaction of folding the display such that the first area faces the second area and a second folding interaction of folding the display such that a first cover corresponding to the first area faces a second cover corresponding to the second area while the first screen is displayed, and in response to detecting the first folding interaction, displaying a second screen related to the first screen on the exposure area, and in response to detecting the second folding interaction, displaying a third screen related to the first screen on one of the first area and the second area, and the first screen. 
     In response to an incoming telephone call, the first screen is a screen for indicating the telephone call, one of the second screen and the third screen may be a screen for refusing the telephone call, and an other screen of the second screen and the third screen may be a screen for accepting the telephone call. 
     In response to the first screen including information, one of the second screen and the third screen may be a screen including brief summary information of the information. 
     In response to the first screen including one or more application icons, one of the second screen and the third screen may be a screen where each of the one or more application icons is classified and included in a corresponding folder according to its classification. 
     The method may further include displaying a visual effect of changing an object or an image content on the display. 
     According to an aspect of another exemplary embodiment, there is provided a displaying method of a user terminal device including a display which is divided into a first area and a second area by a folding line, the second area being larger than the first area and including an exposure area that is exposed while the display is folded along the folding line such that the first area faces the second area, the method including displaying a first screen on the exposure area, detecting at least one of an unfolding interaction of unfolding the display and a folding interaction of folding the display such that a first cover corresponding to the first area faces a second cover corresponding to the second area, and in response to detecting the unfolding interaction, displaying a second screen related to the first screen on the first area and the second area, and in response to detecting the folding interaction, displaying a third screen related to the first screen on the first area or the second area. 
     In response to the first screen including information, one of the second screen and the third screen may be a screen including detailed information of the information. 
     According to an aspect of another exemplary embodiment, there is provided a displaying method of a user terminal device including a display which is divided into a first area and a second area by a folding line, the second area being larger than the first area and including an exposure area that is exposed while the display is folded along the folding line such that the first area faces the second area, the method including displaying a first screen on the first area and the second area, detecting at least one of a first flap interaction of folding the display forward up to a predetermined angle range and then unfolding the display and a second flap interaction of folding the display backward up to a predetermined angle range and then unfolding the display, and in response to detecting the first flap interaction, displaying a second screen related to the first screen on the second area, and in response to detecting the second flap interaction, displaying a third screen related to the first screen on the second area. 
     In response to the first screen including information, one of the second screen and the third screen may be a screen including brief summary information of the information, and an other screen of the second screen and the third screen may be a screen including detailed information of the information. 
     In response to the first screen being a screen including an image content, one of the second screen and the third screen may be a screen displaying the image content magnified, and an other screen of the second screen and the third screen may be a screen displaying the image content reduced. 
     According to an aspect of still another exemplary embodiment, there is provided a user terminal device including a display which is divided into a first area and a second area by a folding line, the second area being larger than the first area and including an exposure area that is exposed while the display is folded along the folding line such that the first area faces the second area, the device including a display configured to display a first screen on the first area and the second area, a detector configured to detect, while the first screen is displayed, a first folding interaction of folding the display such that the first area faces the second area and a second folding interaction of folding the display such that a first cover corresponding to the first area faces a second cover corresponding to the second area, and a controller configured to, in response to detecting the first folding interaction, display a second screen related to the first screen on the exposure area, and in response to detecting the second folding interaction, display a third screen related to the first screen on the first area or the second area. 
     In response to an incoming telephone call, the first screen may be a screen for indicating the telephone call, one of the second screen and the third screen may be a screen for refusing the telephone call, and an other screen of the second screen and the third screen may be a screen for accepting the telephone call. 
     In response to the first screen including information, one of the second screen and the third screen may be a screen including brief summary information of the information. 
     In response to the first screen including one or more application icons, one of the second screen and the third screen may be a screen where each of the one or more application icons is classified and included in a corresponding folder according to its classification. 
     The controller may control the display to display a visual effect of changing an object or an image content on the display. 
     According to an aspect of yet another exemplary embodiment, there is provided a user terminal device including a display which is divided into a first area and a second area by a folding line, the second area being larger than the first area and including an exposure area that is exposed while the display is folded along the folding line such that the first area faces the second area, the device including a display configured to display a first screen on the exposure area, a detector configured to detect an unfolding interaction of unfolding the display and a folding interaction of folding the display such that a first cover corresponding to the first area faces a second cover corresponding to the second area, and a controller configured to, in response to detecting the unfolding interaction, displaying a second screen related to the first screen on the first area and the second area, and in response to detecting the folding interaction, displaying a third screen related to the first screen on the first area or the second area. 
     In response to the first screen including information, one of the second screen and the third screen may be a screen including detailed information of the information. 
     According to an aspect of another exemplary embodiment, there is provided a user terminal device including a display which is divided into a first area and a second area by a folding line, the second area being larger than the first area and including an exposure area that is exposed while the display is folded along the folding line such that the first area faces the second area, the device including a display configured to display a first screen on the first area and the second area, a detector configured to detect a first flap interaction of folding the display forward up to a predetermined angle range with reference to the folding line and then unfolding the display and a second flap interaction of folding the display backward up to a predetermined angle range and then unfolding the display, and a controller configured to, in response to detecting the first flap interaction, display a second screen related to the first screen on the second area, and in response to detecting the second flap interaction, display a third screen related to the first screen on the second area. 
     In response to the first screen including information, one of the second screen and the third screen may be a screen including brief summary information of the information, and an other screen of the second screen and the third screen may be a screen including detailed information of the information. 
     In response to the first screen being a screen including an image content, one of the second screen and the third screen may be a screen displaying the image content magnified, and an other screen of the second screen and the third screen may be a screen displaying the image content reduced. 
     Meanwhile, according to an aspect of another exemplary embodiment, a computer readable recording medium where a program for executing the above-described method is recorded may be provided. 
     In addition, another method for realizing an aspect of an exemplary embodiment, another system, and a computer readable recording medium where a computer program for executing the above-described method may be further provided. 
     As described above, according to various exemplary embodiments, a user may perform various functions of a user terminal device through a UI displayed on the exposure area even when the display is folded, and may be provided with various information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects of exemplary embodiments will become more apparent from the following description with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram illustrating configuration of a user terminal device briefly according to an exemplary embodiment; 
         FIG. 2  is a block diagram illustrating a detailed configuration of a user terminal device according to an exemplary embodiment; 
         FIGS. 3A to 3E  are views illustrating a user terminal device with a rectangular display panel according to an exemplary embodiment; 
         FIG. 4  is a view illustrating a configuration of software stored in a storage according to an exemplary embodiment; 
         FIGS. 5A to 7B  are views illustrating a UI displayed on an exposure area according to various exemplary embodiments; 
         FIGS. 8A to 16B  are views illustrating various exemplary embodiments where a user terminal device performs various functions according to a folding interaction and an unfolding interaction; 
         FIGS. 17A to 34  are views illustrating various exemplary embodiments for maintaining functions of a user terminal device when a folding interaction and an unfolding interaction are detected; and 
         FIGS. 35 to 37  are illustrating a displaying method of a user terminal device according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Specific exemplary embodiments will be described with reference to accompanying drawings and detailed explanation. However, this does not necessarily limit the scope of the exemplary embodiments to a specific form. Instead, modifications, equivalents and replacements included in the disclosed concept and technical scope of this specification may be employed. While describing exemplary embodiments, if a specific description regarding a known technology might obscure the gist of an inventive concept, the specific description may be omitted. 
     In the present disclosure, relational terms such as first and second, and the like, may be used to distinguish one entity from another entity, without necessarily implying any actual relationship or order between such entities. 
     The terms used in the following description are provided to explain a specific exemplary embodiment and are not intended to limit the scope of rights. A singular term includes a plural form unless it expressly says otherwise. The terms, “include”, “comprise”, “is configured to”, etc. of the description are used to indicate that there are features, numbers, steps, operations, elements, parts or a combination thereof, and they should not exclude the possibilities of combination or addition of one or more features, numbers, steps, operations, elements, parts or combination thereof. 
     In an exemplary embodiment, ‘a module’ or ‘a unit’ performs at least one function or operation, and may be realized as hardware, software, or combination thereof. In addition, a plurality of ‘modules’ or a plurality of ‘units’ may be integrated into at least one module and may be realized as at least one processor except for ‘modules’ or ‘units’ that should be realized in a specific hardware. 
     Hereinafter, an exemplary embodiment will be described in detail with reference to accompanying drawings.  FIG. 1  is a block diagram illustrating configuration of a user terminal device  100  according to an exemplary embodiment. As illustrated in  FIG. 1 , the user terminal device  100  includes a display  110 , a detector  120 , and a controller  130 . The user terminal device  100  may be realized as various types of devices, such as a TV, monitor, PC, laptop PC, mobile phone, tablet PC, touchscreen, PDA, MP3 player, kiosk, electronic album, table display device, LCD display, LED display, OLED display, camera, watch, wearable device, etc. If a user terminal device is realized as a portable device, such as mobile phone, tablet PC, PDA, MP3 player, laptop PC, watch, wearable device, etc., the user terminal device may be referred to as a mobile device. Throughout this specification, for convenience and not for any limiting purposes, it may be referred to as a user terminal device. 
     The display  110  displays various image data and UIs. In particular, the display  110  may be realized as a touch screen as it is combined with a touch detector. In addition, the display  110  may include a folding line so that the display  110  may be folded. 
     In particular, the display  110  is divided by a folding line to form a first area and a second area which is larger than the first area. If the display is folded such that the first area comes in touch with the second area, the display  110  may display on an exposure area of the second area, the area exposed while the display  110  is folded, at least one of a UI including information regarding the user terminal device  100  and a UI for controlling the user terminal device  100 . 
     The detector  120  detects a user interaction. In particular, the detector  120  may include a touch detector which detects a user&#39;s touch interaction. In addition, the detector  120  may include a folding detector which detects a folding interaction of folding the display  110  and an unfolding interaction of unfolding the display  110 . 
     The controller  130  controls overall operations of the user terminal device  100 . In particular, if the detector  120  detects a first folding interaction of folding the display  110  forward such that the first area faces the second area with reference to the folding line while a first screen is displayed on the first area and the second area, the controller  130  may control the display  110  to display a second screen related to the first screen on the exposed area of the second area in response to the first folding interaction. In addition, if the detector  120  detects a second folding interaction of folding the display  110  backward such that a first cover corresponding to the first area faces a second cover corresponding to the second area with reference to the folding line while the first screen is displayed on the first area and the second area, the controller  130  may control the display  110  to display a third screen related to the first screen on the first area or the second area. In this case, the first screen, the second screen, and the third screen may be different from one another. 
     One or more exemplary embodiments will be described in greater detail with reference to  FIGS. 2 to 23B .  FIG. 2  is a block diagram illustrating configuration of a user terminal device  200  in detail according to an exemplary embodiment. As illustrated in  FIG. 2 , the user terminal device includes an image receiver  210 , an image processor  220 , a display  230 , a communicator  240 , a storage  250 , an audio processor  260 , a speaker  270 , a detector  280 , and a controller  290 . 
     Meanwhile,  FIG. 2  illustrates various components of the user terminal device  200  having various functions, such as a content providing function, display function, etc. Accordingly, according to one or more exemplary embodiments, a part of the components illustrated in  FIG. 2  may be omitted or changed, or other components may be further added. 
     The image receiver  210  receives image data through various sources. For example, the image receiver  210  may receive broadcasting data from an external broadcasting station, VOD data in real time from an external server, or image data from an external apparatus. 
     The image processor  220  processes image data received from the image receiver  210 . The image processor  220  may perform various image processing with respect to image data, such as decoding, scaling, noise filtering, frame rate conversion, resolution conversion, etc. 
     The display  230  displays at least one of a video frame which is generated as the image processor  220  processes image data received from the image receiver  220  and various screens generated by a graphic processor  293 . 
     In particular, as illustrated in  FIG. 3A , the display  230  may consist of a first area  320  and a second area  330  which is larger than the first area  320  with reference to a folding line  310 . As illustrated in  FIG. 3B , if the display  230  is folded with reference to the folding line  310 , the display  230  may include an exposure area  340  which is the exposed part of the second area  330 . Meanwhile,  FIG. 3C  is a view illustrating a cover which is on the rear side of the user terminal device  200  when the user terminal device  200  is folded. In other words, the rear side of the user terminal device  200  may include a first cover  350  corresponding to the first area  320  and a second cover  360  corresponding to the second area  330 . 
     Meanwhile, in the above-described exemplary embodiment, the length of the folding line  310  is parallel with a short side, but this is only an example. As illustrated in  FIG. 3D , the length of the folding line  310  may be in parallel with a long side. In this case, the display  230  may consist of a first area  370  and a second area  380  with reference to the folding line  310 . As illustrated in  FIG. 3E , if the display  230  is folded with reference to the folding line  310 , the display  230  may include an exposure area  390  of the second area  380 , which is exposed to outside. 
     Meanwhile, in the above-exemplary embodiment, the folding line  310  may be a line generated by a physical hinge. In addition, if the display  230  is a flexible display, the folding line  310  may be a line which can be folded by a user. 
     The communicator  240  performs communication with various types of external apparatuses according to various types of communication methods. The communicator  240  may include a WiFi chip  241 , a Bluetooth chip  242 , a wireless communication chip  243 , and a Near Field Communication (NFC) chip  244 . The controller  290  performs communication with various external apparatuses using the communicator  240 . 
     In particular, the WiFi chip  241  and the Bluetooth chip  242  perform communication according to a WiFi method and a Bluetooth method, respectively. In the case of the WiFi chip  241  or the Bluetooth chip  242 , various connection information, such as an SSID and a session key, may be transmitted/received first for communication connection and then, various information may be transmitted/received. The wireless communication chip  243  represents a chip which performs communication according to various communication standards such as IEEE, Zigbee, 3 rd  Generation (3G), 3 rd  Generation Partnership Project (3GPP), Long Term Evolution (LTE) and so on. The NFC chip  244  represents a chip which operates according to an NFC method which uses 13.56 MHz band among various RF-ID frequency bands such as 135 kHz, 13.56 MHz, 433 MHz, 860-960 MHz, 2.45 GHz, and so on. 
     The storage  250  may store various programs and data necessary to operate the user terminal device  200 . Specifically, the storage  250  may store programs and data to configure various screens to be displayed on a main area and a sub area.  FIG. 4  is a view provided to explain the structure of software stored in the user terminal device  200 . According to  FIG. 4 , the storage  250  may store an Operating System (OS)  410 , a kernel  420 , middleware  430 , an application  440 , etc. 
     The OS  410  controls and manages overall operations of hardware. In other words, the OS  410  manages hardware and is responsible for basic functions such as memory and security. 
     The kernel  420  serves as a path transmitting various signals detected at the display  230 , such as a touch signal, to the middleware  430 . 
     The middleware  430  includes various software modules for controlling the operation of the user terminal device  200 . According to  FIG. 4 , the middleware  430  includes an X11 module  430 - 1 , an APP manager  430 - 2 , a connection manager  430 - 3 , a security module  430 - 4 , a system manager  430 - 5 , a multimedia framework  430 - 6 , a UI framework  430 - 7 , a window manager  430 - 8 , and a writing recognition module  430 - 9 . 
     The X11 module  430 - 1  receives various event signals from various hardware provided in the user terminal device  200 . Herein, the event may vary, ranging from an event of setting of a system alarm, an event of executing or terminating a specific program, etc. 
     The APP manager  430 - 2  manages the execution state of various applications  440  which are installed in the storage  250 . When an application execution event is detected from the X11 module  430 - 1 , the APP manager  430 - 2  calls and executes an application corresponding to the event. 
     The connection manager  430 - 3  supports wired or wireless network connection. The connection manager  430 - 3  may include various detailed modules such as a DNET module, a UPnP module, etc. 
     The security module  430 - 4  supports certification, permission, secure storage, etc., with respect to hardware. 
     The system manager  430 - 5  monitors the state of each element of the user terminal device  200 , and provides the monitoring result to other modules. For example, if there is not enough battery left, an error occurs, or connection is cut off, the system manager  430 - 5  may provide the monitoring result to a main UI framework  430 - 7  or a sub UI framework  430 - 9  and output an alarm message or an alarm sound. 
     The multimedia framework  430 - 6  may be stored in the user terminal device  200 , or may reproduce multimedia content provided from an external source. The multimedia framework  430 - 6  may include a player module, a camcorder module, a sound processing module, etc. Accordingly, the multimedia framework  430 - 6  may reproduce various multimedia content, and generate and reproduce screens and sounds. 
     The main UI framework  430 - 7  provides various UIs to be displayed on a main area of the display  230 , and the sub UI framework  430 - 9  provides various UIs to be displayed on a sub area. The main UI framework  430 - 7  and the sub UI framework  430 - 9  may include an image composite module to configure various objects, a coordinates composite module to calculate a coordinates where an object is to be displayed, a rendering module to render the configured object on the calculated coordinates, a 2D/3D UI toolkit to provide a tool for configuring a UI in 2D or 3D form, etc. The main UI framework  430 - 7  and the sub UI framework  430 - 9  may include an image composite module to configure various objects, a coordinates composite module to calculate a coordinates where an object is to be displayed, a rendering module to render the configured object on the calculated coordinates, a 2D/3D UI toolkit to provide a tool for configuring a UI in 2D or 3D form, etc. 
     The window manager  430 - 8  may detect a touch event using a user&#39;s body part or pen or other input events. When such an event is detected, the window manager  430 - 8  transmits an event signal to the main UI framework  430 - 7  or the sub UI framework  430 - 9  so that an operation corresponding to the event is performed. 
     In addition, if a user touches and drags a screen, various program modules such as a writing module for drawing a line according to a drag trace and an angle calculation module for calculating a pitch angle, a roll angle, a yaw angle, etc. based on a sensor value sensed by a movement detector  282  may be stored. 
     The application module  440  includes applications  440 - 1 - 440 - n  for supporting various functions. For example, program modules for providing various services, such as a navigation program module, a game module, an electronic book module, a calendar module, an alarm management module, a music module, an electronic banking module, a stock module, a calculator module, an electronic mail module, a spreadsheet module, a word processor module, etc. may be included. Such applications may be set as default or may be set temporarily by a user when necessary. If an object is selected, the main CPU  294  may execute an application corresponding to the selected object using the application module  440 . 
     The software structure displayed in  FIG. 4  is only an example and thus, an exemplary embodiment is not necessarily limited thereto. Thus, part of the structure may be omitted or changed, or new structure may be added, if necessary. For example, the storage  250  may additionally provide various programs such as a sensing module for analyzing signals sensed by various sensors, a messaging module including a messenger program, a Short Message Service (SMS) &amp; Multimedia Message Service (MMS) program, an e-mail program, etc., a call info aggregator program module, a VoIP module, a web browser module, etc. 
     Referring back to  FIG. 2 , the audio processor  260  processes audio data of image content. The audio processor  260  may perform various processing such as decoding, amplification, noise filtering, compression, equalization, noise cancellation, echo or reverb removal or addition, etc. with respect to audio data. The audio data processed by the audio processor  260  may be output to the audio output unit  270  (e.g., audio outputter). 
     The audio output unit  270  outputs not only various audio data which is processed in many ways such as decoding, amplification, and noise filtering by the audio processor  260 , but also various alarm sounds or voice messages. In particular, the audio output unit  270  may be realized as a speaker, but this is only an example. The audio output unit  270  may be realized as an output terminal which may output audio data. 
     The detector  280  detects various user interactions. In particular, the detector  280  may include a touch detector  281 , a movement detector  282 , and a folding detector  283 , as illustrated in  FIG. 2 . 
     Specifically, the touch detector  281  may detect a user&#39;s touch interaction using a touch panel attached to the rear side of a display panel. The movement detector  282  may detect a movement (for example, a rotation movement, a vertical movement, a horizontal movement, etc.) of the user terminal device  100  using at least one of an accelerator sensor, a geomagnetic sensor, and a gyro sensor. The folding detector  283  may detect at least one of whether the user terminal device  200  is folded with reference to the folding line  310  and the angle at which the terminal device  200  is folded using a bending sensor (for example, a light sensor, a fiber optic sensor, a conductive ink-based sensor, a conductive fabric sensor, etc.). 
     Meanwhile, the touch detector  281  might activate only a touch sensor disposed on the exposure area while the display  230  is folded, and inactivate a touch sensor disposed on the other areas. 
     The controller  290  controls overall operations of the user terminal device  200  using various programs stored in the storage  250 . 
     As illustrated in  FIG. 2 , the controller  290  includes a RAM  291 , a ROM  292 , a graphic processor  293 , a main CPU  294 , a first to an nth interface  295 - 1 ˜ 295 - n , and a bus  296 . In this case, the RAM  291 , the ROM  292 , the graphic processor  293 , the main CPU  294 , the first to the nth interface  295 - 1 ˜ 295 - n , etc. may be interconnected through the bus  296 . 
     The ROM  292  stores a set of commands for system booting. If a turn-on command is input and thus power is supplied, the main CPU  294  copies O/S stored in the storage  250  to the RAM  291  according to a command stored in the ROM  292 , and boots a system by executing the O/S. When the booting is completed, the main CPU  294  copies various application programs stored in the storage  250  to the RAM  291 , and executes the application programs copied in the RAM  291  to perform various operations. 
     The graphic processor  293  generates a screen including various objects, such as an icon, an image, a text, etc., using an computing unit and a rendering unit. The computing unit (e.g., computer) computes property values such as coordinates, shape, size, and color of each object to be displayed according to the layout of the screen using a control command received from the detector  280 . The rendering unit (e.g., renderer) generates a screen with various layouts including objects based on the property values computed by the computing unit. The screen generated by the rendering unit is displayed in a display area of the display  230 . 
     The main CPU  294  accesses the storage  250 , and performs booting using the O/S stored in the storage  250 . The main CPU  294  performs various operations using various programs, content, data, etc. stored in the storage  250 . 
     The first to the nth interface  295 - 1 ˜ 295 - n  are connected to the above-described various elements. One of the above interface may be a network interface which is connected to an external apparatus via network. 
     In particular, the controller  290  may provide various functions using an exposure area which is exposed to the outside when the display  110  is folded. 
     A UI Provided on the Exposure Area 
     If the display  230  is folded with reference to the folding line  310  such that the first area  320  and the second area  330  come in contact with each other, the controller  290  may control the display  230  to display a predetermined UI on the exposure area  340  of the second area  320 , which is exposed to the outside. In this case, the predetermined UI may include at least one of a UI including the state information of the user terminal device  200  and a UI for controlling the user terminal device  200 . 
     In an exemplary embodiment, if a folding interaction of folding the display  230  with reference to the folding line  310  such that the first area  320  and the second area  330  come in contact with each other is detected, the controller  290  may control the display  230  to display a UI  510  providing a memo function on the exposure area, as illustrated in  FIG. 5A . In this case, if a user input, e.g., a finger, pen, or stylus, is detected through the UI  510  which provides a memo function, the controller  290  may control the display  230  to display an image according to the user input. 
     In addition, the controller  290  may control the display  230  to display a UI for controlling a specific application on the exposure area. Specifically, if a folding interaction of folding the display  230  with reference to the folding line  310  such that the first area  320  and the second area  330  come in contact with each other is detected while a specific application is executed, the controller  290  may control the display  230  to display a UI for controlling the specific application on the exposure area. For example, as shown in  FIG. 5B , if a folding interaction of folding the display  230  with reference to the folding line  310  such that the first area  320  and the second area  330  come in contact with each other is detected while a music application is executed, the controller  290  may control the display  230  to display a UI  520  for controlling the music application on the exposure area. In this case, the UI  520  for controlling a music application may include information regarding currently-played music, a play/stop icon, a skip icon, a rewind icon, a next song, a past song, thumbs up, thumbs down, etc. 
     In addition, the controller  290  may control the display  230  to display a UI including a hot key icon for checking the current state of the user terminal device  200  on the exposure area. For example, if a predetermined user interaction (for example, an interaction of touching or tapping the exposure area twice in a row) is detected while the display  230  is folded, the controller  290  may control the display  230  to display a UI  530  including a hot key icon for checking the current state of the user terminal device  200  on the exposure area as illustrated in  FIG. 5C . In this case, the hot key icon for checking the current state of the user terminal device  200  may include a hot key icon for checking a battery state, a hot key icon for checking a network state, a hot key icon for checking display brightness setting, etc. 
     In addition, the controller  290  may control the display  230  to display a UI informing that a message or data is received from outside on the exposure area. For example, if an social network service (SNS) message is received from outside through the communicator  240  while the display  230  is folded, the controller  290  may control the display  230  to display a UI  540  informing that the SNS message is received on the exposure area as illustrated in  FIG. 5D . In this case, the UI  540  informing that an SNS message is received may include at least one of information regarding a sender and information regarding the SNS message. 
     Further, the controller  290  may control the display  230  to display various types of UIs for releasing a lock state of the user terminal device  200  on the exposure area. 
     Specifically, as illustrated in  FIG. 6A , the controller  290  may control the display  230  to display a UI  610  for inputting a pin number to release the lock state of the user terminal device  200  on the exposure area. In this case, the UI  610  for inputting a pin number may change the pin number by a touch interaction of swiping up and down. If a predetermined pin number is input on the UI  610  displayed on the exposure area, the controller  290  may release the lock state of the user terminal device  200 . Additionally, the user may set the pin number through user input. 
     In addition, as illustrated in  FIG. 6B , the controller  290  may control the display  230  to display a UI  620  including a plurality of dots on a corner of the exposure area to release the lock state of the user terminal device  200  on the exposure area. In this case, if a touch interaction of connecting dots in a predetermined pattern is detected on the UI  620 , the controller  290  may release the lock state of the user terminal device  200 . Additionally, the user may set the pattern through user input. 
     As illustrated in  FIG. 6C , the controller  290  may control the display  230  to display a UI  630  in the form of a keyboard, i.e., piano, to release the lock state of the user terminal device  200  on the exposure area. In this case, if a touch interaction of touching the keyboard in a predetermined rhythm is detected on the UI  630 , the controller may release the lock state of the user terminal device  200 . Additionally, the user may set the rhythm through user input. 
     In addition, as illustrated in  FIG. 6D , the controller  290  may control the display  230  to display a UI  640  including a home icon to release the lock state of the user terminal device on the exposure area. In this case, if a touch interaction of pinching out with reference to the home icon included in the UI  640  is detected, the controller  290  may release the lock state of the user terminal device  200 . 
     The controller  290  may control the display  230  to display a UI for changing the setting of the user terminal device  200  on the exposure area. 
     Specifically, as illustrated in  FIG. 7A , the controller  290  may control the display  230  to display a UI  710  in the form of an arc for adjusting the volume of the user terminal device  200 . Meanwhile, in the above exemplary embodiment, the UI displayed on the exposure area adjusts the volume, but this is only an example. A UI for adjusting another setting of the user terminal device  200  (for example, display brightness, etc.) may be displayed. 
     In addition, as illustrated in  FIG. 7B , if a touch interaction of dragging one of a plurality of vertexes included in the exposure area in a diagonal direction is detected, the controller  290  may control the display  230  to display a UI  730  for turning off the power of the user terminal device  200  at the corner area corresponding to the vertex where the touch interaction is detected. 
     A Folding Interaction and an Unfolding Interaction 
     If a plurality of icons are displayed on the exposure area while the display  230  is folded, and an unfolding interaction of unfolding the display  230  while one of the plurality of icons is touched, the controller  290  may control the display  230  to display a screen corresponding to the touched icon on full screen. 
     Specifically, as illustrated in  FIG. 8A , the display  230  displays first to fourth icons  810  to  840  while the display  230  is folded. If an unfolding interaction of unfolding the display  230  is detected while the fourth icon  840  out of the first to the fourth icon  810  to  840  is touched, the controller  290  may control the display  230  to display a full screen message window  850  corresponding to the fourth icon  840 , as illustrated in  FIG. 8B . 
     Meanwhile, in the above exemplary embodiment, an unfolding interaction is detected while the fourth icon  840  is touched, but this is only an example. If an unfolding interaction is detected while another icon is touched, a screen corresponding to the other touched icon may be displayed on the full screen of the display  230 . For example, if an unfolding interaction is detected while the first icon  810  is touched, the controller  290  may control the display  230  to display a full screen execution screen of a call application corresponding to the first icon  810  (for example, a recent call list screen, an address book screen, a call sending screen, etc.). In addition, if an unfolding interaction is detected while the second icon  820  is touched, the controller  290  may control the display  230  to display a web browser screen corresponding to the second icon  820  on full screen. If an unfolding interaction is detected while the third icon  830  is touched, the controller  290  may control the display  230  to display a full screen execution screen of a music application corresponding to the third icon  830  (for example, a music play screen, a music list screen, etc.). 
     In addition, if the exposure area is touched while the display  230  is folded and then, an unfolding interaction of unfolding a hinge angle of the display  230  as much as a predetermined angle is detected, the controller  290  may control the display  230  to display a screen for executing a specific function. 
     Specifically, if a call request is received while the display  230  is folded, the controller  290  may control the display  230  to display a UI  910  informing that a call request is received on the exposure area, as illustrated in  FIG. 9A . If an unfolding interaction of unfolding a hinge angle of the display  230  as much as a predetermined angle (for example, 70° to 120°) is detected while the UI  910  informing that a call request is received is touched, the controller  290  may accept the call request, execute a speaker phone function, and control the display  230  to display an execution screen  920  including various icons, as illustrated in  FIG. 9B . 
     Specifically, if a message is received from outside while news information  1010  is displayed at the same as the display  230  is folded, the controller  290  may control the display  230  to display a UI  1020  informing that the message is received along with the news information  1010  on the exposure area as illustrated in  FIG. 10A . If an unfolding interaction of unfolding a hinge angle of the display  230  as much as a predetermined angle (for example, 70° to 120°) is detected while the UI  1020  informing that a message is received is touched, the controller  290  may control the display  230  to display a message window  1030  for writing a reply to the received message, as illustrated in  FIG. 10B . 
     In addition, the controller  290  may control the display  230  to display different screens when the exposure area is touched and then, an unfolding interaction is detected and when an unfolding interaction is detected. 
     Specifically, the controller  290  may control the display  230  to display a UI  1110  corresponding to a music application on the exposure area as illustrated in  FIG. 11A . 
     If a message is received from outside while the UI  1110  corresponding to a music application is displayed on the exposure area, the controller  290  may control the display  230  to display a UI  1120  informing that the message is received along with the music application UI  1110  on the exposure area as illustrated in  FIG. 11B . 
     In this case, if an unfolding interaction of unfolding the display  230  is detected while the exposure area is not touched, the controller  290  may control the display  230  to display an execution screen  1130  of the existing music application as illustrated in  FIG. 11C . In this case, a UI  1135  informing that a message is received may be displayed on one area of the execution screen  1130  of the music application for a predetermined time. 
     However, if an unfolding interaction of unfolding the display  230  is detected while the UI  1120  informing that a message is received is displayed on the exposure area, the controller  290  may control the display  230  to display a message window  1140  for writing a reply to the received message as illustrated in  FIG. 11D . 
     In addition, the controller  290  may control the display  230  to display different screens in the order of detecting an unfolding interaction and a touch interaction for lock-releasing. 
     Specifically, as illustrated in the left side of  FIG. 12A , if a touch interaction for lock-releasing is detected while a UI  1210  for releasing the lock of the user terminal device  200  is displayed on the exposure area, the controller  290  may release the lock state of the user terminal device  200 , and as illustrated in the right side of  FIG. 12A , may control the display  230  to display a first home screen  1220  including time information on the exposure area. 
     In addition, as illustrated in the left side of  FIG. 12B , if a touch interaction for lock-releasing is detected while the UI  1210  for releasing the lock of the user terminal device  200  is displayed on the exposure area, and an unfolding interaction is detected, the controller  290  may release the lock state of the user terminal device  200 , and as illustrated in the right side of  FIG. 12B , may control the display  230  to display a second home screen  1230  on full screen. 
     As illustrated in the left side of  FIG. 12C , if an unfolding interaction is detected while an image is not displayed on the exposure area, the controller  290  may control the display  230  to display a UI  1240  for releasing the lock of the user terminal device on full screen as illustrated in the right side of  FIG. 12C . If a touch interaction for lock-releasing is detected on the UI  1240  for releasing the lock of the user terminal device  200 , which is displayed on full screen, the controller  290  may release the lock state of the user terminal device  200 , and as illustrated in the right side of  FIG. 12B , may control the display  230  to display the second home screen  1230  on full screen. 
     In addition, the controller  290  may control the display  230  to display distinctively a screen which is displayed when only an unfolding interaction is detected while a UI corresponding to a specific application is displayed on the exposure area and a screen which is displayed when an unfolding interaction is detected after the exposure area is touched. 
     Specifically, if a call request is received from outside while the display  230  is folded, the controller  290  may control the display  230  to display a UI  1310  informing a call request is received on the exposure area as illustrated in the left side of  FIG. 13A . If the UI  1310  displayed on the exposure area is touched and then an unfolding interaction of unfolding the display  230  is detected, the controller  290  may control the display  230  to display an execution screen  1320  of a calendar application which is related to a call request function on full screen (in another example, an execution screen of a memo application) as illustrated in the lower left side of  FIG. 13A . On the other hand, if an unfolding interaction of unfolding the display  230  is detected while the UI  1310  displayed on the exposure area is not touched, the controller  290  may control the display  230  to display a call screen  1330  on full screen as illustrated in the lower right side of  FIG. 13A . 
     If a folding interaction of folding the display  230  is detected while a music application is executed, the controller  290  may control the display  230  to display a UI  1340  for controlling the music application on the exposure area as illustrated in the upper portion of  FIG. 13B . If the UI  1340  displayed on the exposure area is touched and then, an unfolding interaction of unfolding the display  230  is detected, the controller  290  may control the display  230  to maintain music play and display a play list  1350  on full screen as illustrated in the lower left side of  FIG. 13B . On the other hand, if an unfolding interaction of unfolding the display  230  is detected while the UI  1340  displayed on the exposure area is not touched, the controller  290  may control the display  230  to display a music player screen  1360  on full screen as illustrated in the lower right side of  FIG. 13B . 
     If a first unfolding interaction of unfolding a hinge angle of the display  230  as much as a predetermined angle is detected, the controller  290  may control the display  230  to display at least one icon for executing a specific function. If a second unfolding interaction of unfolding the display  230  completely while at least one icon is touched, the controller  290  may execute a function corresponding to the touched icon. 
     According to an exemplary embodiment, if a call request is received from outside while the display  230  is folded, the controller  290  may control the display  230  to display a UI  1410  informing that a call request is received on the exposure area as illustrated in  FIG. 14A . 
     If the first unfolding interaction of unfolding a hinge angle of the display  230  as much as a predetermined angle (for example, 30° to 150°) is detected while the UI  1410  informing that a call request is received is displayed, the controller  290  may control the display  230  to display a UI  1420  including a plurality of icons  1430 - 1  to  1430 - 3  for performing various functions in relation with making a call as illustrated in  FIG. 14B . 
     If an unfolding interaction of completely unfolding the display  230  (that is, unfolding the display  230  such that a hinge angle of the display  230  becomes 180°) is detected while a photo sharing icon is touched from among the plurality of icons  1430 - 1  to  1430 - 3 , the controller  290  may accept a call request, and as illustrated in  FIG. 14C , may control the display  230  to display a call screen  1440  on the upper area and a list  1450  for selecting a photo to be shared. In this case, if a touch interaction of dragging one of a plurality of photos included in the list  1450  to the call screen  1440  is selected, the controller  290  may control the communicator  240  to transmit the photo where the touch interaction is detected to a receiver. 
     If an unfolding interaction is detected, the controller  290  may control the display  230  to display a plurality of guidance messages according to a hinge angle of the display  230  while the unfolding interaction is detected. In this case, the guidance messages may include a guidance message for informing an incoming text message, a guidance message for informing a missed call, a guidance message for informing an incoming an SNS message, a guidance message for informing of application updates, etc. 
     Specifically, as illustrated in  FIG. 15A , the controller  290  may control the display  230  to display one guidance message  1510  while the display  230  is folded. Subsequently, if an unfolding interaction of unfolding the display  230  is detected, the controller  290  may control the display  230  to display a different number of guidance messages according to a hinge angle of the display  230 . For example, if a hinge angle of the display  230  is within a first angle range (for example, between 5° and 15°), the controller  290  may control the display  230  to display two guidance messages  1510 ,  1520 . If a hinge angle of the display  230  is within a second angle range (for example, between 15° and 25°), the controller  290  may control the display  230  to display three guidance messages  1510 ,  1520 ,  1530 . That is, the controller  290  may increase the number of guidance messages displayed as a hinge angle of display  230  becomes greater. 
     If a hinge angle of the display  230  is within a fourth angle range (for example, between 35° and 45°), the controller  290  may control the display  230  to display five guidance messages (possibly overlapping)  1510  to  1550 , as illustrated in  FIG. 15B . In this case, as illustrated in  FIG. 15B , the first guidance message  1510  which is updated most recently may be disposed on the top. 
     As illustrated in  FIG. 15B , if an folding interaction of folding the display  230  again is detected when the second guidance message  1520  is touched while the five guidance messages  1510  to  1550  are displayed, the controller  290  may control the display  230  to display the second guidance message  1520  on the exposure area as illustrated in  FIG. 15C . 
     In addition, as illustrated in  FIG. 15B , if an unfolding interaction of unfolding the display  230  completely is detected when the second guidance message  1520  is touched while the five guidance messages  1510  to  1550  are displayed, the controller  290  may control the display  230  to display a screen corresponding to the second guidance message  1520  on full screen as illustrated in  FIG. 15D . 
     Further, the controller  290  may perform different functions according to the direction of a touch interaction which is detected on the exposure area while the display  230  is folded. 
     Specifically, if a message is received from outside while the display  230  is folded, the controller  290  may control the display  230  to display a UI  1610  informing that the message is received on the exposure area as illustrated in  FIG. 16A . 
     In this case, if a touch interaction in the left-and-right direction is detected on the UI  1610  informing that a message is received, the controller  290  may control the display  230  to display a UI informing the previous message or the next message on the exposure area according to the touch interaction. 
     If a touch interaction in the down direction is detected on the UI  1610  informing that a message is received, the controller  290  may delete a currently-received message. 
     If a touch interaction in the up direction is detected on the UI  1610  informing that a message is received, the controller  290  may store the received messages. Specifically, as illustrated in  FIG. 16B , if a touch interaction in the up direction is detected on a UI  1620  informing that a first message is received, a touch interaction in the up direction is detected on a UI  1630  informing a second message is received, a touch interaction in the up direction is detected on a UI  1640  informing that a third message is received and then, an unfolding interaction of unfolding the display  230  is detected, the controller  290  may control the display  230  to display a screen  1620 ′ including the first message, a screen  1630 ′ including the second message, a screen  1640 ′ including the third message and a home screen  1650  as illustrated in  FIG. 16B . 
     Maintain the Current Function Despite the Change in the Shape of the Display  230   
     The controller  290  may maintain the current function even if the shape of the display  230  changes according to a folding interaction or an unfolding interaction, and control the display  230  to display a screen corresponding to the current function. 
     According to an exemplary embodiment, if a folding interaction of folding the display  230  is detected while a music application is executed, the controller  290  may control the display  230  to display a UI  1710  corresponding to the music application on the exposure area as illustrated in  FIG. 17A . If a call request is received while the UI  1710  corresponding to the music application is displayed on the exposure area, the controller  290  may control the display  230  to display a UI  1720  informing that a call request is received on the exposure area as illustrated in  FIG. 17B . If an unfolding interaction of unfolding the display  230  is detected while the UI  1720  informing that a call request is received is displayed on the exposure area, the controller  290  may control the display  230  to display a call screen  1730  on full screen as illustrated in  FIG. 17C . Subsequently, when the telephone call is completed, the controller  290  may control the display  230  to display an execution screen  1740  of the music application on full screen as illustrated in  FIG. 17D . If a folding interaction of folding the display  230  is detected again, the controller  290  may control the display  230  to display the UI  1710  corresponding to the music application on the exposure area as illustrated in  FIG. 17E . 
     According to another exemplary embodiment, as illustrated in  FIG. 18A , the controller  290  may control the display  230  to display an execution screen  1810  of a music application on full screen while the music application is executed. If a call request is received from outside, the controller  290  may control the display  230  to display a screen  1820  for confirming whether to accept the call request as illustrated in  FIG. 18B . If a folding interaction of folding the display  230  is detected while the screen  1820  for confirming whether to accept the call request is displayed, the controller  290  may control the display  230  to display a UI  1830  informing that a call request is rejected on the exposure area as illustrated in  FIG. 18C . When the telephone call is completed, the controller  290  may control the display  230  to display a UI  1840  corresponding to the music application on the exposure area as illustrated in  FIG. 18D . Subsequently, if an unfolding interaction of unfolding the display  230  is detected again, the controller  290  may control the display  230  to display the execution screen  1810  of the music application on full screen as illustrated in  FIG. 18E . 
     The controller  290  may determine a display area which can be watched by a user according to a hinge angle of the display  230 , and control the display  230  to display a screen including different amount of information on the determined display area. In this case, the hinge angle of the display  230  may be matched with the watchable display area and then stored. According to an exemplary embodiment, if the display  230  is unfolded while a telephone call is performed, the controller  290  may control the display  230  to display a first telephone call screen  1910  on full screen as illustrated in  FIG. 19A . 
     If a hinge angle of the display  230  is folded as much as Θ while a telephone call is performed, the controller  290  may determine a display area corresponding to the hinge angle, and as illustrated in  FIG. 19B , may control the display  230  to display a second telephone call screen  1920  on the determined display area. In this case, the second telephone call screen  1920  may include less information and fewer icons than those included in the first telephone call screen  1910 . 
     In addition, if the display  230  is folded while a telephone call is performed, the controller  290  may control the display  230  to display a UI  1930  informing that a telephone call is being performed on the exposure area as illustrated in  FIG. 19C . 
     According to another exemplary embodiment, if the display  230  is unfolded while a navigation application is executed, the controller  290  may control the display  230  to display a first navigation screen  2010  on full screen as illustrated in  FIG. 20A . 
     If a hinge angle of the display  230  is folded as much as Θ while a navigation application is executed, the controller  290  may determine a display area corresponding to the hinge angle, and as illustrated in  FIG. 20B , may control the display  230  to display a second navigation screen  2020  on the determined display area. In this case, the area guided by the second navigation screen  2020  may be smaller than the area guided by the first navigation screen  2010 . 
     If the display  230  is folded while a navigation application is executed, the controller  290  may control the display  230  to display a third navigation screen  2030  on the exposure area as illustrated in  FIG. 20C . In this case, the third navigation screen  2030  may include only direction information and distance information instead of a map screen included in the first navigation screen  2010  and the second navigation screen  2020 . However, a map screen may also be included on the exposure area in third navigation screen  2030 . 
     Whenever a folding interaction or an unfolding interaction is detected, the controller  290  may control the display  230  to reconfigure and display information such that the information corresponds to the size and direction of a screen. 
     Specifically, as illustrated in  FIG. 21A , if a folding interaction of folding the display  230  is detected while a first address book list  2110  is displayed on full screen, the controller  290  may control the display  230  to display a second address book list  2120  on the exposure area as illustrated in  FIG. 21B . In this case, the first address book list  2110  might include user information such as image, name, telephone number, direct call icon, etc., and the second address book list  2120  might include user information such as image and name only, but the display is not limited to this. 
     In addition, as illustrated in  FIG. 22A , if an unfolding interaction of unfolding the display  230  is detected while a news title  2210  is displayed on the exposure area when the display  230  is folded, the controller  290  may control the display  230  to display a screen  2220  including not only the news title but also the news image and the news text as illustrated in  FIG. 22B . 
     In addition, the controller  290  may control the display  230  to display different information on the exposure area and the hidden area when the display  230  is folded. In this case, as illustrated in  FIG. 23A , the controller  290  may control the display  230  to display common information on an exposure area  2310  and private information on a hidden area  2320 . For example, as illustrated in  FIG. 23B , the controller  290  may control the display  230  to display barcode information which is common information on the exposure area  2330 , and credit card list and transaction information which is private information on the hidden area  2340 . 
     Function Change According to Change in Angle where the Display is Folded 
     According to an exemplary embodiment, while the display  230  is folded forward such that the first area  320  faces the second area  330  which is larger than the first area  320  with reference to the folding line  310  of the display  230 , the controller  290  may control the display  230  to display the first screen on the exposure area  340  which is an exposed area of the second area  330 . For example, the first screen may include at least one of an image content, an object, an application, and a text. If the detector  280  detects an unfolding interaction of unfolding the display  230  with reference to the folding line  310  while the first screen is displayed, the controller  290  may control the display  230  to display the second screen related to the first screen on the first area  320  and the second area  330 . If the detector  280  detects a folding interaction of folding the display  230  backward such that the first cover  350  corresponding to the first area  320  faces the second cover  370  corresponding to the second area  330  with reference to the folding line  310 , the controller  290  may control the display  230  to display the third screen related to the first screen on the first area  320  or the second area  330 . 
     In this case, the state that the first area  320  and the second area  330  facing each other means a state where the display  230  is folded forward such that a plane including the first area  320  is in parallel or substantially parallel with a plane including the second area  330 . Alternatively, the state that the first area  320  and the second area  330  facing each other means a state where the display  230  is folded forward up to a predetermined angle range (for example, 160° to 180°) such that the display  230  is unfolded first and then, the first area  320  faces the second area  330 . The state that first area  320  and the second area  330  facing each other may also mean a state where the display  230  is folded forward such that the first area  320  comes into contact with the second area  330 . 
     Similarly, the state that the first cover  350  and the second cover  360  facing each other means a state where the display  230  is folded backward such that a plane including the first cover  350  is in parallel or substantially parallel with a plane including the second cover  360 . Alternatively, the state that the first cover  350  and the second cover  360  facing each other means a state where the display  230  is folded backward up to a predetermined angle range (for example, 160° to 180°) such that the display  230  is unfolded first and then, the first cover  350  faces the second cover  360 . The state that first cover  350  and the second area  360  facing each other may also mean a state where the display  230  is folded backward such that the first cover  350  comes into contact with the second cover  360 . 
     Hereinafter, an exemplary embodiment will be described in greater detail with reference to  FIGS. 24 and 25 . 
       FIG. 24  is a view illustrating an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  2410  of  FIG. 24 , the controller  290  may control the display  230  to display a first screen  2411  including common information (for example, a mail sender name or a mail-related object) on the exposure area  340  which is an exposed area of the second area  330 . While the first screen  2411  is displayed, the detector  280  may detect an unfolding interaction of unfolding the display  230 . 
     If the detector  280  detects an unfolding interaction, as illustrated in  2420  of  FIG. 24 , the controller  290  may control the display  230  to display a second screen  2421  with a widget  2421 - 1  including detailed common information (for example, the main text of a mail) on the first area  320  and the second area  330 . In this case, the second screen  2421  may also include other widgets  2421 - 2 ,  2421 - 3 . While the second screen  2421  is displayed, the detector  280  may detect a folding interaction of folding the display  230  backward such that the cover  350  corresponding to the first area  320  faces the cover  360  corresponding to the second area  330  with reference to the folding line  310 . 
     If the detector  280  detects a folding interaction of folding the display  230  backward, as illustrated in  2430  of  FIG. 24 , the controller  290  may control the display  230  to display a third screen  2431  including detailed common information (for example, the main text of a mail) on the second area  330 . While the third screen  2431  is displayed, the detector  280  may detect a flip interaction of flipping the user terminal device  200 . 
     If the detector  280  detects a flip interaction, as illustrated in  2440  of  FIG. 24 , the controller  290  may control the display  230  to display a fourth screen  2441  including a common information list on the first area  320 . The common information list may include, for example, identification information regarding a sender who sends a mail, a mail title, part of the main text of a mail, and common information regarding the state of the user terminal device  200 . The common information may be accumulated and displayed in the order where the information is received. For example, the common information which is generated most recently may be on the top of the common information list. 
     In another example, in  2420  of  FIG. 24 , if the detector  280  detects a folding interaction of folding backward, the controller  290  may control the display  230  to display the third screen  2431  including the detailed common information on the second area  330  and to display the fourth screen  2441  including the common information list on the first area  320 . 
       FIG. 25  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  2510  of  FIG. 25 , the controller  290  may control the display  230  to display a home screen  2511  including a plurality of widgets on the first area  320  and the second area  330 . While the home screen  2511  is displayed, the detector  280  may detect a flap interaction of folding the display  230  forward up to a predetermined angle range (for example, more than 30°) with reference to the folding line  310  and then, unfolding the display  230  again. 
     If the detector  280  detects the flap interaction, as illustrated in  2520  of  FIG. 25 , the controller  290  may control the display  230  to display a home screen  2521  including application icons. While the home screen  2521  is displayed, the detector  280  may detect a folding interaction of folding the display  230  backward such that the first cover  350  corresponding to the first area  320  faces the second cover  360  corresponding to the second area  330  with reference to the folding line  310 . 
     If the detector  280  detects the folding interaction, as illustrated in  2530  of  FIG. 25 , the controller  290  may control the display  230  to display a folder screen  2531  including a plurality of folders on the second area  330 . In this case, each of the folders on the folder screen  2531  may include application icons which are classified according to their properties. While the folder screen  2531  is displayed, the detector  280  may detect a flip interaction of flipping the user terminal device  200 . 
     If the detector  280  detects the flip interaction, as illustrated in  2540  of  FIG. 25 , the controller  290  may control the display  230  to display a common information list screen  2541  including a common information list on the first area  320 . 
     According to another exemplary embodiment, the controller  290  may control the display  230  to display the first screen on the first area  320  and the second area  330 . While the first screen is displayed, the detector  280  may detect the first folding interaction of folding the display  230  forward up to a predetermined angle range with reference to the folding line  310 , or the second folding interaction of folding the display  230  backward up to a predetermined angle range. 
     If the detector  280  detects the first folding interaction, the controller  290  may control the display  230  to display the second screen related on the first screen on the exposure area  340  which is an exposed area of the second area  330 . On the other hand, if the detector  280  detects the second folding interaction, the controller  290  may control the display  230  to display the third screen related to the first screen on the first area  320  or the second area  330 . 
     Hereinafter, another exemplary embodiment will be described in greater detail with reference to  FIG. 26 . 
       FIG. 26  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  2610  of  FIG. 26 , the controller  290  may control the display  230  to display a telephone call request screen  2611  for requesting a telephone call from outside on the first area  320  and the second area  330 . While the telephone call request screen  2611  is displayed, the detector  280  may detect the first folding interaction of folding the display  230  forward to up to a predetermined angle range, or the second folding interaction of folding the display  230  backward up to a predetermined angle range. In this case, folding the display  230  forward up to a predetermined angle range may be, for example, folding the display  230  forward with reference to the folding line  310  such that the first area  320  faces the second area  330 . In addition, folding the display  230  backward up to a predetermined angle range may be, for example, folding the display  230  backward at more than 90° with reference to the folding line  310  such that the user terminal device  200  can stand on the floor. 
     If the detector  280  detects the first folding interaction, as illustrated in  2620  of  FIG. 26 , the controller  290  may control the display  230  to display a telephone call refusal screen  2621  including an object or a text for refusing the telephone call request. On the other hand, if the detector  280  detects the second folding interaction, as illustrated in  2630  of  FIG. 26 , the controller  290  may accept the telephone call request, execute a speaker phone function, and control the display  230  to display a telephone call acceptance screen  2631  including icons for controlling various functions of a telephone call. 
     Hereinafter, various exemplary embodiments wherein a visual effect of the user terminal device  200  illustrated in  FIG. 2  where an object or an image content changes while the display  230  is folded will be described with reference to  FIGS. 27 to 29 . 
       FIG. 27  is a view provided to explain an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction according to another exemplary embodiment. 
     As illustrated in  2710  of  FIG. 27 , the controller  290  may control the display  230  to display a home screen  2711  including application icons on the first area  320  and the second area  330 . While the home screen  2721  is displayed, the detector  280  may detect a folding interaction of folding the display  230  backward with reference to the folding line  310 . 
     If the detector  280  detects the folding interaction, as illustrated in  2720  of  FIG. 27 , the controller  290  may control the display  230  to display a visual effect of moving each of the application icons of the home screen  2711  to a respective folder. Specifically, as the angle at which the display  230  is folded increases, the controller  290  may control the display  230  to display a process where the application icons gradually move upward and enter categorized folders. 
     If the detector  280  keeps detecting a folding interaction and detects a folding interaction of folding the display  230  such that the cover  350  corresponding to the first area  320  faces the cover  360  corresponding to the second area  330 , as illustrated in  2730  of  FIG. 27 , the controller  290  may control the display  230  to display a folder screen  2731  with folders including application icons on the second area. 
       FIG. 28  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  2810  of  FIG. 28 , the controller  290  may control the display  230  to display a screen  2811  including common information (for example, a mail sender name or a mail-related object) on the exposure area  340  which is an exposed part of the second area  330 . While the screen  2811  is displayed, the detector  280  may detect an unfolding interaction of unfolding the display  230 . 
     If the detector  280  detects the unfolding interaction, the controller  290  may control the display  230  to display a visual metaphor effect of spreading a folder according to the angle where the display  230  is unfolded. Specifically, if the angle where the display  230  is unfolded is within the first angle range (for example, 5°˜90°), as illustrated in  2820  of  FIG. 28 , the controller  290  may control the display  230  to display titles of common information of a common information list. If the angle where the display  230  is unfolded is within the second angle range (for example, 90°˜160°), as illustrated in  2830  of  FIG. 28 , the controller  290  may control the display  230  to display titles and a part of main texts of common information of a common information list. If the angle where the display  230  is unfolded is within the third angle range (for example, 160°˜180°), as illustrated in  2840  of  FIG. 28 , the controller  290  may control the display  230  to display a screen  2841  with a widget including detailed common information. 
       FIG. 29  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  2910  of  FIG. 29 , the controller  290  may control the display  230  to display a screen  2911  including common information (for example, an envelope object) on the exposure area  340  which is an exposed part of the second area  330 . While the screen  2911  is displayed, the detector  280  may detect an unfolding interaction of unfolding the display  230 . 
     If the detector  280  detects the unfolding interaction, as illustrated in  2920  of  FIG. 29 , the controller  290  may control the display  230  to display a visual metaphor effect that a letter appears after the envelop opens. Specifically, as the angle where the display  230  is unfolded increases, the controller  290  may control the display  230  to display the process that the envelop opens and the main contents of a letter appear gradually. 
     If the detector  280  detects an unfolding interaction of unfolding the display  230  completely, as illustrated in  2930  of  FIG. 29 , the controller  290  may control the display  230  to display a screen  2931  including detailed common information (for example, the main text of a mail). 
     According to another exemplary embodiment, the controller  290  may control the display  230  to display the first screen on the second area  330 , and to display the second screen related to the first screen on the first area  320 . 
     While the first screen and the second screen are displayed, the detector  280  may detect a flap interaction of folding the display  230  up to a predetermined angle range (for example, more than 30°) with reference to the folding line  310  and unfolding the display  230  again. If the detector  280  detects the flap interaction, the controller  290  may control the display  230  to keep displaying the first screen on the second area  330  and to display the third screen related to the first screen instead of the second screen on the first area  320 . 
     Hereinafter, another exemplary embodiment will be described in greater detail with reference to  FIGS. 2 and 30 to 32 . 
       FIG. 30  illustrates an exemplary embodiment of performing various functions of the user terminal device illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  3010  of  FIG. 30 , the controller  290  may control the display  230  to display a message transmission screen  3011  including a message to be transmitted to a counterpart and a transmission button for transmitting a message on the second area  330  and to display a keypad screen  3012  for inputting a text to be displayed on the message display screen  3011  on the first area  320 . While the keypad screen  3012  is displayed, the detector  280  may detect a flap interaction of folding the display  230  forward up to a predetermined angle range (for example, more than 30°) with reference to the folding line and then, unfolding the display  230  again. 
     If the detector  280  detects the flap interaction, as illustrated in  3020  of  FIG. 30 , the controller  290  may control the display  230  to display the message transmission screen  3011  continuously on the second area  330 , and to display a clip board screen  3021  including a previously-copied text or a captured image instead of the keypad screen  3012  on the first area  320 . While the clip board screen  3021  is displayed, the detector  280  may detect a flap interaction of folding the display  230  again with reference to the folding line  310  and unfolding the display  230 . 
     If the detector  280  detects the flap interaction, as illustrated in  3030  of  FIG. 30 , the controller  290  may control the display  230  to display a gallery screen  3031  including images stored in the user terminal device  200  or in an external server instead of the clip board screen  3021 . While the gallery screen  3031  is displayed, the detector  280  may detect a user interaction of touching and selecting at least one of the images included in the gallery screen  3031  and dragging or flipping the selected image in the direction of the second area  330 . 
     If the detector  280  detects the user interaction, as illustrated in  3040  of  FIG. 30 , the controller  290  may control the display  230  to display the message transmission screen  3011  including the selected image on the second area  330 . In this case, if the detector  280  detects a touch interaction of selecting a transmission button of the message transmission screen  3011 , the controller  290  may control the communicator  240  to transmit a message with an image included in the message transmission screen  3011  to a counterpart. 
     Meanwhile, if the detector  280  detects a flap interaction while the gallery screen  3031  is displayed, the controller  290  may control the display  230  to display the keypad screen  3012  again instead of the gallery  3031  on the first area  320 . 
       FIG. 31  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  3110  of  FIG. 31 , the controller  290  may control the display  230  to display a gallery screen  3111  including images on the first area  320  and the second area  330 . While the gallery screen  3111  is displayed, the detector  280  may detect a flap interaction of folding the display  230  again with reference to the folding line  310  and unfolding the display  230 . 
     If the detector  280  detects the flap interaction, as illustrated in  3120  of  FIG. 31 , the controller  290  may control the display  230  to display part of the gallery screen  3111  on the second area  330  and to display a message transmission screen  3121  on the first area  320 . While the message transmission screen  3121  is displayed, the detector  280  may detect a flap interaction of folding the display  230  again with reference to the folding line  310  and unfolding the display  230 . 
     If the detector  280  detects the flap interaction, as illustrated in  3130  of  FIG. 31 , the controller  290  may control the display  230  to display a notice screen  3131  for registering a content in a notice provided by a social network service (for example, Facebook, Twitter, etc.) instead of the message transmission screen  3121 . While the notice screen  3131  is displayed, the controller  290  may detect a user interaction of touching at least one of the images included in the gallery screen  3111  and dragging or flipping the selected image in the direction of the first area  320 . 
     If the detector  280  detects the user interaction, as illustrated in  3140  of  FIG. 31 , the controller  290  may control the display  230  to display the notice screen  3131  including the selected image on the second area  330 . In this case, if the detector  280  detects a touch interaction of selecting a notice button on the notice screen  3131 , the controller  290  may control the communicator  240  to transmit the image included in the notice screen  3131  to a social network server so that the image can be shared with a third party. 
     Meanwhile, if the detector  280  detects a flap interaction while the notice screen  3131  is displayed, the controller  290  may control the display  230  to display the gallery screen  3111  again on the first area  320  and the second area  330 . 
       FIGS. 32A to 32D  illustrate an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  3210  of  FIG. 32A , the controller  290  may control the display  230  to display a memory list screen  3211  including memos on the first area  320  and the second area  330 . While the memo list screen  3211  is displayed, the detector  280  may detect a flap interaction of folding the display  230  with reference to the folding line  310  and unfolding the display  230 . 
     If the detector  280  detects the flap interaction, as illustrated in  3220  of  FIG. 32A , the controller  290  may control the display  230  to display part of the memo list screen  3211  on the first area  320  and to display a memo writing screen  3221  on the second area  330 . While the memo writing screen  3221  is displayed, the controller  290  may detect a user interaction of tap-touching one area of the memo writing screen  3221 . 
     If the detector  280  detects the user interaction, as illustrated in  3230  of  FIG. 32B , the controller  290  may control the display  230  to move upward and display the memo writing screen  3221  on the first area  320 , and to display a keypad screen  3231  on the second area  330 . While the keypad screen  3231  is displayed, the detector  280  may detect a user interaction of panning in one direction on the keypad screen  3231 . 
     If the detector  280  detects the user interaction, as illustrated in  3240  of  FIG. 32B , the controller  290  may control the display  230  to display a gallery screen  3241  including images on the second area  330 . While the gallery screen  3241  is displayed, the detector  280  may detect a user interaction of long-tapping and selecting one of the images included in the gallery screen  3241 . 
     If the detector  280  detects the user interaction, as illustrated in  3250  of  FIG. 32C , the controller  290  may control the display  230  to display a visual effect of moving the selected image to the first area  320 . 
     In addition, as illustrated in  3260  of  FIG. 32C , the controller  290  may control the display  230  to display the memo writing screen  3221  including the selected image on the first area. While the selected image is included in the memo writing screen  3221 , the detector  280  may detect a user interaction tapping a storage button for executing the function of storing a written memo. 
     If the detector  280  detects the user interaction, as illustrated in  3270  of  FIG. 32D , the controller  290  may store the content of the memo writing screen  3221  including images as a memo, and may control the display  230  to display the memo list screen  3211  including the stored memo on the first area  320 . The controller  290  may control the display  230  to display a toast pop-up  3271  informing that the memo is stored for a few seconds (for example, 1-2 seconds). 
       FIG. 33  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  FIG. 3310  of  FIG. 33 , the controller  290  may control the display  230  to display a screen  3311  including an image content on the first area  320  and the second area  330 . While the screen  3311  is displayed, the detector  280  may detect a first flap interaction of folding the display  230  backward up to a predetermined angle range with reference to the folding line  310  and unfolding the display  230 . In addition, the detector  280  may detect a second flap interaction of folding the display  230  forward up to a predetermined angle range with reference to the folding line  310  and unfolding the display  230 . 
     If the detector  280  detects the first flap interaction, as illustrated in  3320  of  FIG. 33 , the controller  290  may control the display  230  to display a screen  3321  including a magnified image content on the first area  320  and the second area  330 . In this case, the controller  290  may change a magnification ratio of the image content according to the angle where the display  230  is folded backward with reference to the folding line  310 . For example, the greater the angle where the display  230  is folded, the higher the magnification ratio of the image content. 
     On the other hand, if the detector  280  detects the second flap interaction, as illustrated in  3330  of  FIG. 33 , the controller  290  may control the display  230  to display a screen  3331  including a reduced image content on the first area  320  and the second area  330 . In this case, the controller  290  may change a reduction ratio of an image content according to the angle where the display  230  is folded forward with reference to the folding line  310 . For example, the greater the angle where the display  230  is folded, the higher the reduction ratio of the image content. 
       FIG. 34  illustrates an exemplary embodiment of performing various functions of the user terminal device  200  illustrated in  FIG. 2  based on a folding interaction. 
     As illustrated in  3410  of  FIG. 34 , the controller  290  may control the display  230  to display a screen  3411  including an information list on the first area  320  and the second area  330 . If the information list is, for example, a feed list for sharing information with members of a specific group through a social network service, the information list may include at least one of identification information of a counterpart who registers the information, a text, an image content, and icons. While the screen  3411  is displayed, the detector  280  may detect the first flap interaction of folding the display  230  backward up to a predetermined angle range with reference to the folding line  310  and unfolding the display  230 . Alternatively, the detector  280  may detect the second flap interaction of folding the display  230  forward up to a predetermined angle range with reference to the folding line  310  and unfolding the display  230 . 
     If the detector  280  detects the first flap interaction, as illustrated in  3420  of  FIG. 34 , the controller  290  may control the display  230  to summarize and display information included in the first area  320  as screen  3421 . Specifically, the controller  290  may control the display  230  to display the titles feeds included in the first area  320  as if they fall down and accumulated in a gravity direction. 
     On the other hand, if the detector  280  detects the second flap interaction after the display  230  is folded forward, as illustrated in  3430  of  FIG. 34 , the controller  290  may control the display  230  to magnify and display information included in the first area  320  as screen  3431 . Specifically, the controller  290  may control the display  230  to magnify cards of the feeds included in the first area  320  so that the cards including more detailed content can be displayed. 
       FIG. 35  is a flowchart illustrating a displaying method of the user terminal device  200  according to an exemplary embodiment. 
     Specifically, the user terminal device  200  may display a first screen on the display  230  which is divided into the first area  320  and the second area  330  which is larger than the first area with reference to the folding line  310  (S 3510 ). 
     The user terminal device  200  may determine whether a first folding interaction of folding the display  230  forward is detected, or a second folding interaction of folding the display  230  backward is detected (S 3520 ). In this case, the first folding interaction may be a folding interaction of folding the display  230  forward such that the first area  320  faces the second area  330  with reference to the folding line  310 . The second folding action may be a folding interaction of folding the display backward such that the first cover  350  corresponding to the first area  320  faces the second cover  360  corresponding to the second area  330  with reference to the folding line  310 . 
     If the first folding interaction is detected, the user terminal device  200  may display a second screen related to the first screen on the exposure area  340  which is an exposed part of the second area  330  (S 3530 ). On the other hand, if the second folding interaction is detected, the user terminal device  200  may display a third screen related to the first screen on the first area  320  or the second area  330  (S 3540 ). 
       FIG. 36  is a flowchart illustrating a displaying method of the user terminal device  200  according to another exemplary embodiment. 
     Specifically, the user terminal device  200  may display the first screen on the exposure area  340  which is an exposed part of the second area while the display  230  is folded forward such that the first area  320  faces the second area  330  with reference to the folding line  310  (S 3610 ). 
     The user terminal device  200  may determine whether an unfolding interaction of unfolding the display  230  is detected, or a folding interaction of folding the display  230  backward is detected (S 3620 ). In this case, the folding interaction may be a folding interaction of folding the display  230  backward such that the first cover  350  corresponding to the first area  320  faces the second cover  360  corresponding to the second area  330  with reference to the folding line  310 . 
     If the unfolding interaction is detected, the user terminal device  200  may display the second screen related to the first screen on the first area  320  and the second area  330  (S 3630 ). On the other hand, if the folding interaction is detected, the user terminal device  200  may display the third screen related to the first screen on the first area  320  or the second area  330  (S 3640 ). 
       FIG. 37  is a flowchart illustrating a displaying method of the user terminal device  200  according to another exemplary embodiment. 
     Specifically, the user terminal device may display the first screen on the display  230  which is divided into the first area  320  and the second area  330  which is larger than the first area  320  with reference to the folding line (S 3710 ). 
     The user terminal device  200  may determine whether a first flap interaction of folding the display  230  forward up to a predetermined angle range with reference to the folding line  310  and then, unfolding the display  230  is detected, or a second flap interaction of folding the display  230  up to a predetermined angle range with reference to the folding line  310  and then, unfolding the display  230  is detected (S 3720 ). 
     If the first flap interaction is detected, the user terminal device  200  may display the second screen related to the first screen on the second area  330  (S 3730 ). On the other hand, if the second flap interaction is detected, the user terminal device  200  may display the third screen related to the first screen on the second area  330  (S 3740 ). 
     As described above, a UI is displayed on an exposure area which is an exposed area when the display  230  is folded and thus, a user may perform various functions of a user terminal device through the UI displayed on the exposure area even if the display is folded and may be provided with various information. 
     A displaying method of a user terminal device according to the above-described various exemplary embodiments may be realized as a program and provided in the user terminal device. Specifically, a non-transitory computer readable medium where a program including a method for controlling a user terminal device is stored can be provided. 
     The non-transitory recordable medium refers to a medium which may store data semi-permanently and may be readable by an apparatus. Specifically, the non-transitory readable medium may be CD, DVD, hard disk, Blu-ray disk, USB, memory card, ROM, etc. 
     The foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of exemplary embodiments of the present inventive concept is intended to be illustrative, and not to limit the scope of the claims, and the disclosure includes many alternatives, modifications, and variations apparent to those skilled in the art.