Some keyboards and typewriters have a key called shift lock. It is a lot like the caps lock key in that letters you type will be in uppercase instead of lowercase. But shift lock also does something else: when it is on, keys which have two symbols on them, such as the number keys in the top row, will print the symbol on top, instead of the symbol on the bottom. For example, pressing the key with the number 1 on it will print the exclamation mark ("!") instead of the number 1. The caps lock key does not do this; it only affects the letter keys.