what is structure in c

what is structure in c

an array is one kind of data structures that can be used to demonstrate a group of data items that belongs to the same type like int, float, char, double etc. But if we want to represent or demonstrate a collection of different types of data items using a single name, then we cannot use an array. For this reason, in C language supports a user defined data type known as structure. Actually, structure is user defined data type available in C that allows combining different kinds of data items using a single name.

On the other word, a structure is a well-situated tool for handling a collection of logically related data items. It is used to represent a record or a set of attributes, such as student_name, roll_number, obtained_mark and cgpa etc. It is a powerful concept that we can often need to use in our program design. 

STRUCTURE DEFINITION/DECLARATION
A structure is a collection of deferent type variables under a single name. Structures assist to arrange complex data in a more meaningful. A structure declaration or definition generates a format that can be used to declare structure variables. To define a structure, we must use the keyword struct statement. The keyword struct statement defines a new data type, with more than one member. It declares a structure to hold the details of member fields. The general format of the structure definition is as follows:

struct struct_tag_name

{
data_type member-1;
data_type member-2;
data_type member-3;
………… …. ….
……….. …. ….
data_type member-n;
} one or more structure variables;

Here, the struct_tag_name is called structure tag name and it is optional and each member definition is a normal variable definition, such as int a, float b, char c or char c[] etc; or any other valid variable definition. The tag name may be used subsequently to declare variables that have the tag structure. The fields are called structure elements or members. Each member may belong to different type of data. At the end of the structure's definition, before the final semicolon, you can specify one or more structure variables. Let us use an example to illustrate the process of structure definition and the creation of structure variables. Consider a book data base consisting of book title, author name, subject, number of pages, price and book id. We can define a structure to hold this information as follows: 

struct Books

{
char title[50];
char author[50];
char subject[100];
int pages;
float price;
int book_id;
}book;

 

We can declare structure variables using structure tag name anywhere in the program. For instance, the statement

struct Books book, book1, book2, book3;

declares book, book1, book2 and book3 as variables of type struct Books

ACCESSING STRUCTURE MEMBERS
If we want to access any member or field of a structure, we may use the “member access operator (.)” also called dot operator or period operator. The member access operator (.) is coded as a period between the structure variable name and the structure member that we wish to access.

For example
book.title
book.price
book. book_id

are the variables representing the title, price and book id of book and can be treated like any other
ordinary variable. Here is how we should assign values to the members of book:

strcpy(book.title, “ C Programming”);
strcpy(book.author, “ Amran Hossain”);
book.pages=300;
book.price=500.00;
book.book_id=34521;

 We can also use scanf() function to give the values through the keyword

scanf(“%s\n”,book.title);
scanf(“%s\n”,book.author);
scanf(“%d\n”,book.pages);
scanf(“%f\n”,book.price);
scanf(“%d\n”,book.book_id);
are valid input statements.

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