A display device comprising: a memory configured to store a content; a display panel configured to output at least a portion of the content; a plurality of contact points disposed on a side surface of the display device and including a data port; a sensor configured to detect an inclination angle of the display device about the direction of gravity through the sensor; and a control circuit electrically connected with the memory, the display panel, the plurality of contact points, and the sensor, wherein a first contact point of the plurality of contact points is configured to contact with a second contact point disposed on a side surface of an external display device, and wherein when the first contact point is in contact with the second contact point, the control circuit is configured to: receive information related to the external display device through the data port of the first contact point and the data port of the second contact point, the information includes a size and a resolution of the external display device; determine a virtual quadrangle region defined by a maximum length of the display device and the external display device along a vertical axis in the direction of gravity and along a horizontal axis based on the received information and positions of the first contact point and the second contact point, the virtual quadrangle region including a first region corresponding to the display device, a second region corresponding to the external display device, and a third region where the content is not output on any device, wherein the virtual quadrangle region is formed such that the virtual quadrangle region is not inclined about the direction of gravity; map the content to the virtual quadrangle region; output a first portion of the content mapped to the determined first region of the virtual quadrangle region to the display panel of the display device; and transmit data corresponding to a second portion of the content to the external display device through the data port of the first contact point and the data port of the second contact point. a memory configured to store a content; a display panel configured to output at least a portion of the content; a plurality of contact points disposed on a side surface of the display device and including a data port; a sensor configured to detect an inclination angle of the display device about the direction of gravity through the sensor; and a control circuit electrically connected with the memory, the display panel, the plurality of contact points, and the sensor, wherein a first contact point of the plurality of contact points is configured to contact with a second contact point disposed on a side surface of an external display device, and wherein when the first contact point is in contact with the second contact point, the control circuit is configured to: receive information related to the external display device through the data port of the first contact point and the data port of the second contact point, the information includes a size and a resolution of the external display device; determine a virtual quadrangle region defined by a maximum length of the display device and the external display device along a vertical axis in the direction of gravity and along a horizontal axis based on the received information and positions of the first contact point and the second contact point, the virtual quadrangle region including a first region corresponding to the display device, a second region corresponding to the external display device, and a third region where the content is not output on any device, wherein the virtual quadrangle region is formed such that the virtual quadrangle region is not inclined about the direction of gravity; map the content to the virtual quadrangle region; output a first portion of the content mapped to the determined first region of the virtual quadrangle region to the display panel of the display device; and transmit data corresponding to a second portion of the content to the external display device through the data port of the first contact point and the data port of the second contact point. receive information related to the external display device through the data port of the first contact point and the data port of the second contact point, the information includes a size and a resolution of the external display device; determine a virtual quadrangle region defined by a maximum length of the display device and the external display device along a vertical axis in the direction of gravity and along a horizontal axis based on the received information and positions of the first contact point and the second contact point, the virtual quadrangle region including a first region corresponding to the display device, a second region corresponding to the external display device, and a third region where the content is not output on any device, wherein the virtual quadrangle region is formed such that the virtual quadrangle region is not inclined about the direction of gravity; map the content to the virtual quadrangle region; output a first portion of the content mapped to the determined first region of the virtual quadrangle region to the display panel of the display device; and transmit data corresponding to a second portion of the content to the external display device through the data port of the first contact point and the data port of the second contact point.