Notes for computer science and engineering branch. Subject Computer programming through c language

UNIT- 7

STRUCTURES AND UNIONS

Basic of Structures

 Structures variables

 Initialization

 Structure assignment

 Structures and arrays: arrays of structures,

Basic of Structures: -

    1.   Structure is a user defined data-type.

    2.   Structure is a complex data-type.

    3.   Structure is a collection of heterogeneous variables.

    4.   Structure allows to store both primitive and derived data-types i.e. arrays and pointers at one place under one name.

    5.   Structure allows to carry different types of variables at a time.

SYNTAX: -

          

struct [<structure- tag- name>]  {here, struct is a key-word}

        {

               data-type variables;

               data-type variables;

        }

        [structure variables];

To access the structure members we should have to use the following syntax

structure variable . structure members

It is called accessing/ invoking the structure members.

Here . (dot) operator is called: -

    1.   Member access operator.

    2.   Field access operator.

    3.   Member of operator.

    4.   Membership operator.

     5.   Belongs to operator.

EXAMPLE: -

         struct stu      <------------------------ tag name

         {

                 int id;                                 {int, char, float are structure members}

                 char name[100];

                 float fee;

         }

         s1, s2;       <------------------------ structure variables

Structures and arrays: arrays of structures: -

    1.   Perhaps the most common usage of structures is in arrays of structures.

    2.   To declare an array of structures, we must first define a structure and then declare an array variable of that type.

    3.   For example, to declare a 100-student array of type student

struct  student

{

         int  rno;

         char name[50];

         int m1, m2, m3, total;

float average;

                 };

                 struct student s[100];

                

UNION: -

    

    1.   Union is a keyword.

    2.   Like the structure union are also used to place several variables of different data-type under one name. But the main difference is all union members are having common memory/ one memory.

    3.   Size of structure is sum of all the structures members but union size is biggest union members.

    4.   Union is a user defined.

SYNTAX: -

         union [<union- tag- name>]  

        {

               data-type variables;

               data-type variables;

        }

        [union variables];

Example: - FINDING UNION SIZE

#include<stdio.h>

#include<conio.h>

void main()

{

    union stu;

{

             int id;

             char name[50];

float fee;

} s;

void main

{

         clrscr();

         printf(“Union size is %d bytes”, sizeof(s));

         getch();

}

Output: -

Union size is 50 bytes