Also known as "all caps". Uppercase refers to text written solely in the capital letters of the alphabet, as opposed to lowercase letters.
Because Uppercase letters are typically larger and more visually prominent than lowercase letters, uppercase can be used as headlines or titles, sometimes for aesthetic purposes. It is important to use uppercase appropriately in order to communicate effectively as it is also commonly used as typographical emphasis or used to indicate words spoken by someone who is shouting which can be considered as poor etiquette, especially in personal settings. Uppercase reduces readability in most cases, especially when applied to longer words and sentences or when text is not large as each letter would share the same x-height making letters hard to be distinguished. However, the visual distinction of uppercase also allows it to stand out, even without any design treatment. In online chats or SMS, uppercase is sometimes used accidentally when the cap lock key or shift key is on.
It is not a common typography treatment but occasionally used for aesthetic or artistic purposes (in poetry, for example). Another application is to use it in desktop instant messaging as it does not require any additional typings on the Shift key to capitalize any letters. Additionally, lowercase is often favored in programming languages to avoid coding errors. A developer may use lowercase words or acronyms, sometimes connected by dashes or underscores, as variables, file names, or class/ID names in various programming languages.