Struct

You can access the members , the way you are trying( but the structures which are inside the union should have unique members) but you should make sure that while compiling the code gcc should know that you are trying like that, command : gcc -fms-extensions file_name.

The syntaxes to declare or define a structure and a union are similar . The major difference between a structure and a union is storage. In a structure, each member has its distinct storage location while the members of a union utilize a shared memory location that is equal to the size of its largest data member.

A structure can be nested inside a union and it is called union of structures. It is possible to create a union inside a structure.

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.