Structure and Union full explaination in C Programming

           C-Programming:-

In this tutorials you will learn:-

 Structure :-

 

It is a collection of different data type variable group together under a single name.

Syntax :-

struct  structure name 

{

data type  mem 1 ;

data type  mem 2 ;

data type  mem 3 ;

, , , ,  , , ,    , , , , , , 

, , , ,  , , ,    , , , , , , 

data type  mem n;

 Declaration of structure:-

struct book 

{

int pages ;

char name [ 100 ] ;

float price ;

} b ;

There are 3 types of declaration of structure :-

1. struct book 

{

int pages ;

char name [ 100 ] ;

float price ;

} ;

 struct book b ;

2. Struct book 

{

int pages ;

char name [ 100 ] ;

float price ;

} b ;

3. struct 

{

int pages ;

char [ 100 ] ;

float ;

} b ;

 Initializing and accessing of declaration :-

The link between a member and a structure variable is establish using member operator and dot operator. 

Struct book 

{

int pages ;

char name [ 100 ] ;

float price ;

} b = {   100    ,  codeswithabhi  ,  1000.234  } ;

             page            name                price      

By using member operator :-

struct book 

{

int pages ;

char name [ 30 ];

float price ;

};

struct book b;

b.pages = 100 ;

strcpy ( b. name , : codeswithabhi");

b.price = 345.32; 

so here we see the use of member operator in structure 

Let see one example of structure for understand every point ..

#include<stdio.h>

struct book 

{

int pages ;

char name [ 100 ] ;

float price ;

};

int main (  )

{

struct book  b ;

printf("enter pages , book name , price of book");

scanf("%d%s%f ", &b.pages , b.name , &b.price);

printf("\n details of books are ");

printf(" pages of book are = %d", b.pages);

printf("writer name = %s", b.name);

printf(" price of book = %d",b.price);

return ( 0 );

}

OUTPUT

enter pages , writer name , price of books  1600

codeswithabhi

234.23

 details of book are 

pages of books = 1600

write name  =  codeswithabhi

price of books = 234.23

Array of structure :-

Array of structure means collection of structure array storing different type of structure variable 

For example :-

#include<stdio.h>

struct result 

{

int rollno ;

char name [ 30 ] ;

float marks ;

};

  int main ( )

{

struct result r [ 60 ] ;

int i ;

printf("enter details of student ");

for (i=1 ; i<=60 ; i++)

{

printf("\n enter rollno , name , marks ");

scanf("%d", & r[i].rollno);

scanf("%s", r[i].name );

scanf("%f", & r[i].price);

}

for(i=1 ; i<=60 ; i++)

{

 printf("%d\n",name );

printf('%s\n", rollno);

printf("%f\n",marks);

}

return( 0 ) ;

}

OUTPUT 

enter details 

enter roll no , name , marks 

1

Abhijeet

90.4 

it will be continued up to 60 ....

Pointer to structure :-

 We have already learned that a pointer is a variable which points to the address of another variable of any data type . Similarly we can have a pointer to structure , where a pointer variable can be points to the address of a structure variable. 

Syntax 

struct tag name 

{

member 1 ;

member 2 ;

};

struct tag name  *struct name ;

For example :-

#include<stdio.h>

struct name 

{

int a ;

float b;

};

int main ( )

{

struct name *ptr, p;

ptr = &p;

printf("enter integer no : ");

scanf("%d\n",&(*ptr).a);

printf("enter float value");

scanf("%f\n",  &(*ptr).b);

printf("displaying: ");

printf("%d \ n %/f ", (*ptr).a , (*ptr).b);

return( 0 );

}

OUTPUT

enter integer no 10

enter float value 10.5

a = 10

b = 10.5

Nested structure :-

A structure that contain another structure as a member of a variable is known as nested structure .

For example:-

#include<stdio.h>

int main ()

{

struct address 

{

char city [30];

 char colony [30];

int pin ;

};

struct employ 

{

char name [30];

struct address a;

};

struct employ e = { "abhi" , "kanpur" , "abc" , "208011" } ;

printf("%s\n%s", e.a.colony , e.a.city);

printf("%d\n %s", e.a.pi , e.name );

return( 0 );

}

OUTPUT 

abhi

kanpur 

abc

208011

 Difference between array and structure:-

	Array	Structure
1	An array behave like a built in data type all we have to do this to declare an array variable and use it.	First we have to design and declare a data type structure before the variable are declare and use.
2	An array is the collection of similar data type.	A structure have a collection of different data type.
3	An array is a derived data type,.	A structure is a user defined data type.

  Union :-

* Union is user defined data type just like structure.

* Each member  of structure is assigned it's own unique storage area whereas union all the member share common storage area.

* All member share  common area so only one member can be active at a time.

* Union are used when all the member are not assigned value at the same time.

syntax:-

Union tag name 

{

data type  member 1;

data type  member 2 ;

 };

There are 3 types of declaration of union in C are :-

1.

 union sample 

{

int a;

float b;

char c;

};

union sample s;

2. 

union  sample 

[

int a ;

float b;

 char c;

}s;

3. 

union 

{

int a ;

float b;

char  c;

}s;

Initialization and accessing of union :-

Union sample

{

int a;

float b;

char c;

};

int main ( )  

{
union sample s ={ 10 , 10.5 , 'a' };

printf('%d \ n ", s.a);

printf('%f  \ n", s.b);

printf('%c \ n ", s.c);

return( 0 );

}

OUTPUT

10

10.5

a

Memory status of union and structure :-

1. Union's memory status:-

declare one union--

union sample 

{

int a;

float b;

char c;

} s;

         ----------sample---------

 -------------int a ------

---------------------------float b ----------------

--char c---

As we know that a union share common storage area.

so here, int a takes 2 bytes in memory.

float b takes 4 bytes 

char c 1 byte

so total bytes use during the program is =  4 bytes .

2. Structure:-

Structure's memory status:-

declare one srtucture  -

 struct sample 

{

int a;

float b;

char c;

} s;

 -----sample-----

---------int a ---------

 --- ------------------float b ---------------------------

---char c ---

As we know that the structure's member occupy separate storage area.

so here int a takes separate 2 bytes 

float b takes separate 4 bytes

and char c is separate 1 byte in memory 

then, the total space require by structure is 7 bytes.

 Difference between union and structure :-

	Union	Structure
1.	All member share the same storage area.	Each member is assigned it's own unique storage area .
2.	Maximum memory required by the member is allocated.	Total memory required by all member is allocated.
3.	Only one member is active at a time	All member is active at a time.
4.	Only first member can be initialized	All member can be initialized .
5.	Require less memory.	Require more memory.

Thanks for reading..........