Consortium/community Union

Defining a community is similar to defining struct.

First, define a struct:

Typedef struct

{

Unsigned char floor;

Unsigned char room;

Unsigned short region;

} Position;

 

Define another community

Typedef Union

{

Position lightpos;

Unsigned char posbyte [4];

} P;

 

If the values are as follows:

P. lightpos. Floor = 0x10;

P. lightpos. Room = 0x01;

P. lightpos. region = 0x0501;

 

Then:

P. posbyte [0] = 0x10;

P. posbyte [1] = 0x01;

P. posbyte [2] = 0x01;

P. posbyte [3] = 0x05;

 

That is to say, all members of the community share the memory. When one member is assigned a value, the value of the other member changes accordingly.