Many laptops are equipped with a video port for hooking up an external monitor. Once connected, the bigger screen can be used the same as the laptop's built-in screen. Pressing a sequence of keys on the laptop keyboard makes it possible to turn off the laptop screen to save power and preserved the life of the LCD screen. The sequence is the same, although the correct key to press for shutting down the screen varies with the laptop model.
Raise the laptop screen to reveal the keypad, then locate the Function keys along the top row of the keyboard. The keys are numbered F1 through F12. One of the keys will typically be printed with a small icon of a computer screen. On older laptops, the key may also be printed with "CRT/LCD."
Press and hold the Fn (Function) key in the lower left corner of the keyboard.
Press the numbered F key along the top row of the keyboard that corresponds to the laptop's LCD control. For example, press the F5 key while pressing and holding the Fn key to shut off the laptop monitor.
Press and hold the Fn key and press the numbered F key a second time to turn on the laptop screen.