Structure (srtuct) in c programming

 What is structure (struct) in c

Structure is a collection of heterogeneous data items treated as a single unit. These data items can be of different types. Each data item is called a member of structure. The keyword struct is used to declare structure. The memory of a structure is determined by the sum of memory allocated to all the members of a structure. In this structure, multiple members can be simultaneously accessed at a time.

As we know that an array is the collection of similar data items such as float or int a single entity. It is not possible to hold different data items with different data types in an array, so structure is the best solution to hold dissimilar data items as a single entity.

The syntax for structure declaration

In this example variable 1, variable 2, variable n are the members of the structure and var is a variable with data type tag_name.

struct structure_ name

{

data type variable 1;

data type variable 2;

……………………………..;

data type variable n;

};

struct structure_name var;

Example of structure variable

In this example record is structure type and int roll_no, char fname[30] and char lname[30] are the members of the structure and a is the structure variable

struct record

{
int roll_no;

char fname[30];

char lname[30];

};

struct record a;  

Structure initialization

Structure variable can be initialized quite similar to array. The following example shows the structure initialization process.

sruct student

{

int roll_no;

char fname[30];

char lname[30];

S1={1, “Ram”, “Rai”};

}

The alternative method to initialize structure variable as:

struct student S2={1, “Sita”,”Devi”};

struct student S3={2,”Hari”,”Sharma”};

Accessing structure members

A member of structure can be accessed by using period(.) sign between structure variable and respective member.

Syntax 

Variable.member;

Example

S1.roll_no;

 Example of structure

Write a C program to take student name, roll no, mark, and prints the record on-screen.

  #include<stdio.h>

#include<conio.h>

void main()

{

                struct record

                {

                                int roll;

                                float mark;

                                char name[20];

                };

                struct record a;

                {

                                printf("\n Enter Roll number, Name and marks of student");

                                scanf("%d%s%f", &a.roll, a.name, &a.mark);

                    printf("\n Roll number=%d\tName=%s\t marks=%f",a.roll, a.name, a.mark);

                }

                getch();

}

Output

Feature of structure

It can be treated as a record that is a collection of interrelated data fields having different data types.

It Is possible to copy one structure variable to another by simply assignment operator(=).

It allows a nested structure that is one structure inside another structure.

It is possible to define structure pointer also known as linked list.

Let check another example

Write a c program to take Roll no, Name and mark of 5 students and display it.

#include<stdio.h>

#include<conio.h>

void main()

{

                struct record

                {

                                int roll;

                                float mark;

                                char name[20];

                };

                int i;

                struct record a[5];

                for(i=0;i<5;i++)

                {

                                printf("\n Enter Roll number, Name and marks of student");

                                scanf("%d%s%f",&a[i].roll, a[i].name, &a[i].mark);

                }

                for(i=0;i<5;i++)

                {

                    printf("\n Roll number=%d\tName=%s\t marks=%f",a[i].roll, a[i].name, a[i].mark);

                }

                getch();

}

Output

In this example, we have to print a record of 5 students. It is possible to declare structure as an array; called an array of structure. It is also known as the collection of structure variables having the same set of members. To display 5 students' records we have to make the variable a[5]; as an array.

Difference between structure and union in C

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