UNION in C-LANGUAGE

UNION

Union is a collection of non-homogeneous / heterogeneous / different data type elements that can be grouped together under a common name. Union is also a user-defined data type which is similar to structure.

The general format of a union declaration is:

            Syntax    :       union Tag

                                    {

                                                Datatype Member1;

                                                Datatype Member2;

                                                            - - -

                                                            - - -

                                                Datatype Membern;

                                    };

Where,

Ø  union is a keyword used to declare the union data type.

Ø  Tag is name the union that follows same rules as a valid identifier.

Ø  Members declared inside the union are known as union members (or) union elements.

Ø  Union declaration must be ended with a semicolon.

Example:

union employee

{

int Id;

char Name[25];

long Salary;

};

            Memory is allocated for the union only at the time of creating union variable.  The general form of creating union variables is:

            Syntax                        :           union Tag Variable1, Variable2, - - - - - , Variablep;

           

Example         :           union employee E;

           

For this, the memory allocation will be:

Ø  In union, compiler selects the member which occupies highest memory, and that memory is reserved only.  So, that all the members of the union are shared that common memory.  It implies that, although a union may contain many members of different types, it can handle only one member at a time.

Ø  Dot operator is used to access member of the union with the union variable.  The general format of accessing union members with union variable is:

       #include<stdio.h>

       union employee

       {

              int Id;

              char Name[25];

              long Salary;

       };

       void main()

       {

              union employee E;            

                    printf("\nEnter Employee Id : ");

                    scanf("%d", &E.Id);

                    printf("\n\n Employee Id : %d", E.Id);

                    fflush(stdin);

                    printf("\nEnter Employee Name : ");

                    scanf("%s", &E.Name);

                    printf("\n Employee Name : %s", E.Name);

                    printf("\nEnter Employee Salary : ");

                    scanf("%ld", &E.Salary);

                    printf("\n Employee Salary : %ld", E.Salary);

       }