Introduction to Structure in C

Structure is a user defined data of C language. It is a collection of different values of same or different data types. It is basically used to group logically related data.

In C language, syntax for defining a structure is:

struct <Struct_name>
{
<datatype-1> var1;
<datatype-2> var2;
:
:
<datatype-N> varN;
};

Here, struct is the keyword to start creating a structure in C.

Struct_name is the valid name of structure. 

datatype-1, data-type2,… data-typeN are data types of different structure members. 

var1, var2,… varN are variables  declared inside a structure. They are called structure members.

; Semicolon is needed to end a structure.

Example
struct data
{
int a;
float b;
};

In the above example, structure named data has been defined which contains two elements  named a and b.

Declaration of a Structure variable in C

We can declare variables of a structure just as we declare variables of other data types. 

Syntax:

struct <Struct_name> v1,v2,…..vN;

Here, Struct_name is the name of an existing structure .

v1,v2,……..vN are names of structure variables.

Example:

struct data d;

In the above example, variable d has been declared for already declared structure data.

Accessing structure members in C

Dot (.) operator or arrow operator  -> can be used with the structure variable to work with members of a structure.

The dot operator is required for normal structure variables and arrow operator is required for pointer variables of structure.

The syntax for referring to structure member is:

struct_var.member;
or
struct_var->member;

Here, struct_var is the name of structure variable and member is a structure element.

#include<stdio.h>
struct data
{
int a;
float b;
};
int main()
{
struct data d;
d.a=13;
d.b=20.55;
printf("\nd.a=%d",d.a);
printf("\nd.b=%f",d.b);
return(0);
}

d.a=13
d.b=20.549999

Initialization of a structure variable in C

We can use pair of braces to  initialize a structure variable. 

Syntax:

struct <Struct_name><var>={Values};

Example:        

struct data
{
int a;
float b;
};
struct data d={2,5.5};

In this example, structure variable d has been initialized with values 20,50.5.  20 would be stored in d.a and 50.5 would be stored in d.b .

#include<stdio.h>
struct data
{
int a;
float b;
};
int main()
{
struct data d={3,7.8};
printf("\nd1.a=%d",d1.a);
printf("\nd1.b=%f",d1.b);
printf("\nd.a=%d",d.a);
printf("\nd.b=%f",d.b);
return(0);
}

d.a=3
d.b=7.800000

#include<stdio.h>
struct student
{
char name[25];
int rollno;
float fees;
};

int main()
{
struct student s;
printf("\nEnter Name of student:=");
gets(s.name);
printf("\nEnter rollno:=");
scanf("%d",&s.rollno);
printf("\nEnter fees:=");
scanf("%f",&s.fees);

printf("\nStudent 's Name=%s",s.name);
printf("\nRollno=%d",s.rollno);
printf("\nFees=%f",s.fees);
return(0);
}

Enter Name of student:=Amit
Enter rollno:=1
Enter fees:=5000
Student 's Name=Amit
Rollno=1
Fees=5000.000000