Unions
Unions
Unions are similar to structures but a union’s members all share the same memory location. In essence a union is a variable that is capable of holding different types of data at different times.

Unions:

  • May contain any number of members
  • Members may be of any data type
  • Are as large as their largest member
  • Use exactly the same syntax as structures except struct is replaced with union

Creating an Union

Syntax

union unionName
{
type1 memberName1;

typen memberNamen;
}

Example

Purpose of a Union

Unions are similar to structures EXCEPT that struct by itself outside of a union assigns a new memory location upon declaration

Example

union allows the same memory location to be viewed and manipulated as different data types.

Example

Creating a Union with typedef

Syntax

typedef union unionTagoptional
{
type1 memberName1;

typen memberNamen;
} typeName;

Example

Unions Memory Storage

Union variables may be declared exactly like structure variables. Memory is allocated to accomodate the union's largest member.

Examples

Unions.png
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Example from typical .h file

UnionsFinal.png

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