All caps different from uppercase letter
In typography, all caps (short for "all capitals") refers to text or font in which all letters are capital letters; for example, THIS TEXT IS IN ALL CAPS. They are commonly seen in legal documents, the titles on book covers, in advertisements and in newspaper headlines. Short strings of words in capital letters appear bolder and "louder" than mixed case, and this is sometimes referred to as "screaming" or "shouting". All caps can also be used to indicate that a given word is an acronym.
Studies have been conducted on the readability and legibility of all caps text. Scientific testing from the 20th century onward has generally indicated that all caps text is less legible and readable than lower-case text. In addition, switching to all caps may make text appear hectoring and obnoxious for cultural reasons, since all-capitals is often used in transcribed speech to indicate that the speaker is shouting. All-caps text is common in comic books, as well as on older teleprinter and radio transmission systems, which often do not indicate letter case at all.In professional documents, a commonly preferred alternative to all caps text is the use of small caps to emphasise key names or acronyms (for example, Text in Small Caps), or the use of italics or (more rarely) bold. In addition, if all caps must be used it is customary to slightly widen the spacing between the letters, by around 10 per cent of the point height. This practice is known as tracking or letterspacing. Some digital fonts contain alternative spacing metrics for this purpose.