A display device includes a display screen, at least one data interface, and a processor. The display screen is configured for showing images. The at least one data interface is configured for receiving image signal from a computer. The processor includes a processing unit, a first power source, and a second power source. The processing unit is configured for checking whether the data interfaces receive image signals and inputting the image signals into the display screen if the data interfaces receive image signals. The first power source is configured for supplying power to the processing unit continuously. The second power source is configured for supplying power to the display screen when the processing unit detects if the data interfaces receive image signals.