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Data structures

Grouping data. Tidying up programs.

It would be hard for a program to manipulate data if it were scattered around with no particular structure. C therefore has several facilities to group data together in convenient packages, or data structures. One type of data structure in C is the struct (or structure) data type, which is a group of variables clustered together with a common name. A related data type is the union, which can contain any type of variable, but only one at a time. Finally, structures and unions can be linked together into complex data structures such as lists and trees. This chapter explores all of these kinds of data structure.

It is important to distinguish the terms structure and data structure. "Data structure" is a generic term that refers to any pattern of data in a computer program. An array is a data structure, as is a string. A structure is a particular data type in C, the struct; all struct variables (structures) are data structures, but not all data structures are structures.