A union is a data format that can hold different data types but only one type at a time.
A union can hold an int or a long or a double.
The syntax is like that for a structure.
For example, consider the following declaration:
union my_union
{
int int_val;
long long_val;
double double_val;
};
You can use a my_union variable to hold an int, a long, or a double,just as long as you do so at different times:
my_union y; y.int_val = 15; // store an int cout << y.int_val; y.double_val = 1.8; // store a double, int value is lost cout << y.double_val;