devxlogo

Unions in C++

Unions in C++

Question:
I am trying to find some information on Unions in C++, specifically syntax and some type of example and perhaps a discussion as to when and why they are used.

Answer:
Unions in C++ are mostly the same as unions in C. They provide an easy syntax that you can use to treat an area in memory as different variables.For example, say you had a list of items, and each item needed to hold either an integer or an array of 10 characters at any one time.You could create a structure that contained both data types, but that would waste memory if you used only one at a time. A better approach might be to declare a union.

union MyUnion {   int i;   char s[10];};
This allows you declare a variable of type MyUnion, which you can treat either as an integer or a character array.
union MyUnion x;x.i = 5;     // Use X as an integerx.s[0] = ‘x’ // Use X as a char array
Both i and s occupy the same memory, which you can refer to using either syntax. Note that the space used by a union will be the size of the largest element. In this case, 10 bytes.

devx-admin

Share the Post: