 The GUIs familiar to most people as of the mid-late 2010s are Microsoft Windows, macOS, and the X Window System interfaces for desktop and laptop computers, and Android, Apple's iOS, Symbian, BlackBerry OS, Windows Phone/Windows 10 Mobile, Tizen, WebOS, and Firefox OS for handheld (smartphone) devices.Since the commands available in command line interfaces can be many, complex operations can be performed using a short sequence of words and symbols.This allows greater efficiency and productivity once many commands are learned, but reaching this level takes some time because the command words may not be easily discoverable or mnemonic.