C/C++ arrays allow you to define variables that combine several data items of the same kind but structure is another user defined data type which allows you to combine data items of different kinds.
Structures are used to represent a record, suppose you want to keep track of your books in a library. You might want to track the following attributes about each book:
- Title
- Author
- Subject
- Book ID
Defining a Structure:
To define a structure, you must use the struct statement. The struct statement defines a new data type, with more than one member, for your program. The format of the struct statement is this:
struct [structure tag] { member definition; member definition; ... member definition; } [one or more structure variables];
The structure tag is optional and each member definition is a normal variable definition, such as int i; or float f; or any other valid variable definition. At the end of the structure's definition, before the final semicolon, you can specify one or more structure variables but it is optional. Here is the way you would declare the Book structure:
struct Books { char title[50]; char author[50]; char subject[100]; int book_id; }book;
Accessing Structure Members:
To access any member of a structure, we use the member access operator (.). The member access operator is coded as a period between the structure variable name and the structure member that we wish to access. You would usestruct keyword to define variables of structure type. Following is the example to explain usage of structure
Pointers to Structures:
You can define pointers to structures in very similar way as you define pointer to any other variable as follows:
struct Books *struct_pointer;
Now, you can store the address of a structure variable in the above defined pointer variable. To find the address of a structure variable, place the & operator before the structure's name as follows:
struct_pointer = &Book1;
To access the members of a structure using a pointer to that structure, you must use the -> operator as follows:
struct_pointer->title;
Let us re-write above example using structure pointer, hope this will be easy for you to understand the concept
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