Atoms can contain any character if they are enclosed within single quotes and an escape convention exists which allows any character to be used within an atom. The syntax {D1,D2,...,Dn} denotes a tuple whose arguments are D1, D2, ... Dn. Tuples are containers for a fixed number of Erlang data types. Any element of a tuple can be accessed in constant time. The arguments can be primitive data types or compound data types.