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A structure is a derived type usually representing a user-defined collection of named members (or components). The members can be of any type, either fundamental or derived (with some restrictions to be noted later), in any sequence. In addition, a structure member can be a bit field type not allowed elsewhere. The structure type lets you handle complex data structures almost as easily as single variables. Structure initialization is discussed in Arrays, structures, and unions in the help topic Initialization.

In C++, a structure type is treated as a class type with certain differences: default access is public, and the default for the base class is also public. This allows more sophisticated control over access to structure members by using the C++ access specifiers: public (the default), private, and protected. Apart from these optional access mechanisms, and from exceptions as noted, the following discussion on structure syntax and usage applies equally to C and C++ structures.

Structures are declared using the keyword struct. For example

struct mystruct { ... }; // mystruct is the structure tag
struct mystruct s, *ps, arrs[10];
/* s is type struct mystruct; ps is type pointer to struct mystruct;
   arrs is array of struct mystruct. */