STRUCTURES

STRUCTURES:

    

We have seen that arrays can be used to represent a group of data items that belong to the same type, such as int or float. However if we want to represent a collection of data items of different types using a single name, then we cannot use array.

     

C supports a constructed data type known as structure, which is a method of packing data of different data types.

     

A structure is a convenient tool for handling a group of logically related data items.

     

Def:- A structure is a collection of one or more members of different data types grouped together under a single name.

            An array can store more number of elements that belong to same datatype but by using a structure we can store number of elements each of different datatype under the same name.

Declaration of a structure:-

 A structure can be declared as follows:

Syntax:-

Struct tagname

{

data member 1;

data member 2;

:

:

data member n;};

·         The keyword struct is used to declare a structure.

·         The tagname indicates the name of the structure.

·         member 1,member 2,……up to member n are the members of different datatypes which are to be stored under the tagname.

·         The structure declaration should always terminate with a semicolon.

·          The members are not variables by themselves. The members are used to indicate the different datatypes of information that is stored under the tagname.

Declaration of structure variables:-

To access the members of a structure, structure variables are to be declared after the declaration of a structure.

e.g.,

struct student

{

char name[10];

int rollno;

float avg;

};

struct student s1;

Where s1 is the structure variable which occupies 16 bytes(10 for name, 2 for rollno, 4 for avg).

            The structure declaration and variable declaration can be combined as follows:

Struct student

{

char name[20];

int rollno;

float avg;

}s1;

Initialization of a structure:-

Ø  A structure can be initialized as follows:

struct tagname variable={values separated with commas};

Ø  Where order of initialization should be same as order of member declaration.

Eg., struct student s1={“ramya”,20,80.5};

Ø  The values can be initialized to the variables using dot operator(.).

Syntax:-    Variablename.member name=value;

Eg.,         s1.rollno=5;

Ø  Dot operator is also known as member operator or period operator.

Ø  A Program to initialize the structure and display the details.

void main()

{

struct book

{

char name[10];

int pages;

float price;

};

struct book b1={“c& ds”,250,150.5};

 printf(“name=%s”,b1.name);

 printf(“pages=%d”,b1.pages);

 printf(“price=%f”,b1.price);

 getch();

}

Ø  A Program to enter and print details of a structure.

void main()

{

struct book

{

char name[10];

int pages;

float price;

};

struct book b1;

printf(“enter details\n”);

scanf(“%s,b1.name);

scanf(“%d”,&b1.pages);

scanf(“%f”,&b1.price);

printf(“the details are\n”);

 printf(“name=%s”,b1.name);

 printf(“pages=%d”,b1.pages);

 printf(“price=%f”,b1.price);

 getch();

}