Elements

Data structures can be built in main memory, on hard disk, on punch cards, across the Internet, or in any combination of any media that can store bits. Let us simplify things and only talk about data structures built in main memory.

An element in a data structure is an item of data. The "structure" of the data structure consists of the relationships between the elements. Often elements are called nodes. When thinking about the structure part of a data structure each element is an indivisible unit. Here is a picture of the list of the first five prime numbers:

The arrows show the successor and predecessor relationships. The first element of the list has no arrow going into it; the last element of the list has no arrow leaving it. Here is the structure without the data: