Atoms are basic Yacas objects that are used to represent symbols, numbers, and function names. An atom has a string representation which is shown when it is displayed. For example, 3.14159, , A123, +, "good morning" are atoms. Atoms can be of type string, number, or symbol. For example, y1 is a symbolic atom, 954 is a number atom, and "" is an (empty) string atom. Symbolic atoms are normally used in Yacas to denote mathematical unknowns and function names. Number and string atoms are used to denote values. A symbolic atom can be bound to a value (in which case it becomes a variable), or to a rule or several rules (in which case it becomes a function). An atom can also have a property object. See also: Atom , String .