However, each version has so many syntactical differences alone, that this idea was hard to implement. Scheme will be used for the examples in this paper, unless otherwise noted. An atom is a symbol representing anything that the programmer wants. It is a scalar item that cannot be broken down into any smaller elements. A list is a sequence of atoms or other lists enclosed by parentheses.
Lists are important because they provide a structure to group symbols together.
A list can have elements added to, removed from, or manipulated by other functions. In Figure 2b, the fourth example shows a function call that is also a list. The third example in Figure 2b illustrates that lists can be members of lists. In a cons cell, the atom is stored as well as a pointer to the next item or the beginning of the next list. In LISP, every symbol has an associated property list.