Union data type

Union:

• The union is a derived data type and it is declared like structure.
• The difference between union and structure is in terms of storage.
• In structure, each member has its own storage location, whereas all the members of the union use the same location, although the union may contain many members of different types.
• When we use union the compiler allocates a piece of storage that is large enough to hold.

For example,

Name = 30 byte

Roll_num= 2 byte(int data tpe alway take 2 bytes)

Total bytes=32

The structure was taking 32 bytes but the union take the only a maximum number of 30 bytes and use that place.

Memory allocation: 

Syntax:

union union _name

{

data_type variable_name 1;

data_type variable_name 2;

.................................

.................................

data_type variable_name  n;

};

union union _name short_name;

Example program union:

#include<stdio.h>

#include<conio.h>

//Union declaration

union std

{

int roll_num,t,e,m,s,so,tot;

char name[30];

float avg;

};

union std s;//union short name declare

void main()

{

clrscr();

printf("\nEnter student roll number : ");

scanf("%d",&s.roll_num);//calling structure varaiable via 

                                             union short name

printf("\nEnter student name : ");

scanf("%s",&s.name);

printf("\nEnter student five subject mark: ");

scanf("%d %d %d %d %d",&s.t,&s.e,&s.m,&s.s,&s.so);

s.tot=s.t+s.e+s.m+s.s+s.so;

printf("\nTotal mark: %d ",s.tot);

s.avg=s.tot/5;

printf("\nAverage mark: %f ",s.avg);

getch();

}

Output:

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