system), there are a number of ways to input them into a computer system. Apple MacOS, iOS iOS provides accented letters through press-and-hold on most European Latin-script keyboards, including English. Some keyboard layouts feature combining-accent keys that can add accents to any appropriate letter. A letter with double dots can be produced by pressing , then the letter. This works on English and other keyboards and is documented further in the supplied manuals. Google ChromeOS For ChromeOS with US-International keyboard setting, the combination is . For ChromeOS with UK extended setting, use , release, then the letter. Alternatively, the Unicode codepoint may be entered directly, using , release, then the four-digit code, then or . Linux In some Linux desktop environments a letter with double dots can be produced by pressing , then the letter. When the system has a compose key, the same procedure as that described at X-Windows (below) may be used. Microsoft Windows AZERTY and QZERTY keyboards (as used in much of Europe) include precomposed characters (accented letters) as standard and these are fully supported by Microsoft Windows, typically accessed using the AltGr key. For users with a US keyboard layout, Windows includes a setting "US International", which supports creation of accented letters by changing the function of some keys into dead keys. If the user enters ", nothing will appear on screen, until the user types another character, after which the characters will be merged if possible, or added independently at once if not. Otherwise, the desired character may be generated using the Alt table above. For users in the United Kingdom and Ireland with QWERTY keyboards, Windows has an "Extended" setting such that an accented letter can be created using then the base letter. When using Microsoft Word or Outlook, a letter with double dots can be produced by pressing and then the letter. On Microsoft Windows keyboard layouts that do not have double dotted characters, one may use Windows Alt keycodes. Double dots are then entered by pressing the left Alt key, and entering the full decimal value of the character's position in the Windows code page on the numeric keypad, provided that the compatible code page is used as a system code page. One can also use numbers from Code page 850; these are used without a leading 0. X Window System X-based systems with a Compose key set in the system can