Unions are similar to structures but allow sharing of memory between data members. A union stores only one data member at a time, whereas the members of a structure each have their own memory location. Union members share the memory space, which is the size of the largest member. This allows storing different data types in the same memory location but only one value can be stored at a time. Unions are useful for reducing memory usage but require careful management of which member contains a value.

1. C union

2. Defination & introduction
• Unions are con conceptually similar to structures
• The syntax of union is also similar to that of structure
• The only difference is in term of storage
• In structure each member has its own storage location where
the all members of union uses a single shared memory
location which is equal to the size of its largest data
member .
• Data can of int,char,float,double etc .data type
• It is a user defined data type
Note-> union does not support multiple value it can store
only one value at a time
•

3. structure union
Struct emp; union emp
{ {
Char x; //size 1 byte char x;
Float y;//size 4 byte float y;
}e;}e; memory sharing
x y x&y
5 byte 4 byte

4. syntax
Keyword→ union structure _ name
{
data_ type variable 1;
Body data_type variable 2;
…………………………….
data _type variable n;
};

5. example
Union student
{
char name[200];
Int rollno;
Float marks;
};
1.Here student is a the name of union

6. Declaration of union variable
method 1
Union student
{
Char name[200];
Int roll no;
Float marks;
};
Int main()
{
Union student student1;
Return 0;
}

7. Declaration of union variable
method 2
Union student
{
Char name[200];
Int rollno;
Float marks;
}student1;
Int main()
{
Return 0;
}

8. Accessing the data members of
union
• The data member of union can be
accessed as
Union_variable.data_mamber
Example
The rollno of student then we can write as
Student1.rollno

9. Program of union• #include<stdio.h>
• #include<string.h>
• union student
• {
• char name[200];
• int rollno;
• float marks;
•
• }student1;
• int main()
• {
•
• strcpy(student1.name,"ali");
• student1.rollno=201;
• student1.marks=78.5;
• printf("student name=%sn",student1.name);
• printf("student roll no=%dn",student1.rollno);
• printf("student marks=%fn",student1.marks);
• return 0;
• }

10. Program of union• #include<stdio.h>
• #include<string.h>
• union student
• {
• char name[200];
• int rollno;
• float marks;
•
• }student1;
• int main()
• {
•
• strcpy(student1.name,"ali");
• student1.rollno=201;
• student1.marks=78.5;
• printf("student name=%sn",student1.name);
• printf("student roll no=%dn",student1.rollno);
• printf("student marks=%fn",student1.marks);
• return 0;
• }