Almost all smartphones have a screen display of a minimum of 5 inches. Why waste the whole screen!? Feel free to use every inch and enjoy games and videos on a larger display.
To change the screen rotation,
Go to Settings → System → Accessibility.
Turn on the Auto Rotate option.
In recently launched smartphones, the Auto-rotate option is available at the scroll-down bar. Tap to turn it on. It is shown either as Auto-rotate or Portrait mode.
