C Pocket Reference

Structures, Unions, and Bit-Fields

Different data items that make up a logical unit are generally grouped together in a record. The structure of a record—i. e., the names, types, and order of its components—is represented in C by a structure type .

The components of a record are called the members of the structure. Each member can be of any type. The type specifier begins with the keyword struct ; for example:

struct article    {    char   name[40];
                       int    quantity;
                       double price;
                  };

This example declares a structure type with three members. The identifier article is the tag of the structure, and name, quantity, and price are the names of its members. Within the scope of a structure declaration, variables can be declared with the structure type:

struct article  a1, a2, *pArticle, arrArticle[100];

a1 and a2 are variables of type struct article, and pArticle is a pointer to an object of type struct article. The array arrArticle has 100 elements of type struct article.

Structure variables can also be declared simultaneously with the structure type definition. If no further reference is made to a structure type, then its declaration need not include a tag. For example:

struct {unsigned char character, attribute;}
xchar, xstr[100];

The structure type defined here has the members character and attribute, both of which have the type unsigned char. The variable xchar and the elements of the array xstr have the type of the new tagless structure.

The members of a structure variable are located in memory ...