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Unions

A union is a special data type available in C that allows to store different data types in the
same memory location. You can define a union with many members, but only one member can
contain a value at any given time. Unions provide an efficient way of using the same memory
location for multiple purpose.

Defining a Union

To define a union, you must use the union statement in the same way as you did while
defining a structure. The union statement defines a new data type with more than one member for
your program. The format of the union statement is as follows:
union [union tag]

{
member definition;

member definition;
...

member definition;
} [one or more union variables];

The union tag is optional and each member definition is a normal variable definition,
such as int i; or float f; or any other valid variable definition. At the end of the union's definition,
before the final semicolon, you can specify one or more union variables, but it is optional. Here is
the way you would define a union type named Data having three members i, f, and str:
Now, a variable of Data type can store an integer, a floating-point number, or a string of

union Data
{

int i;
float f;

char str[20];
} data;

characters. It means a single variable, i.e., same memory location, can

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