The shortcut to change the letters into capital letters and vice versa

We do not have a problem to write capital letters for writing. Live press the SHIFT key or activate Cap Lock or SHIFT keys. So all the letters we write will be capitalized. Conversely, if you want to present a small case, so avoid it Caps lock and SHIFT keys before, but what if we already wrote the text and want to turn it into capital letters, or to lower case?This is a shortcut to change the