Upper CASE refers to the use of capital letters in writing. It is commonly used at the beginning of sentences, for proper nouns, and in acronyms. For example, the first letter of a person's name, like John, is written in upper CASE as "John." In digital communication, upper CASE can also convey emphasis or shouting. For instance, typing "HELLO" in upper CASE can indicate excitement or urgency. However, overusing upper CASE in text can be perceived as aggressive or difficult to read, so it is important to use it judiciously.