struct S_Data  //遵循1
{
  int data1;
  int data2;
} sData;

union U_Data   //遵循2
{
  unsigned char cd[ 4 ];
  int           id;
} uData;

enum E_Level   //遵循3
{
  A_Level = 0,
  B_Level,
  C_Level,
  D_Level
} eLevel;

int main ( void )
{
  eLevel      = B_Level;
  sData.data1 = 2000;
  uData.id    = sData.data1;

  return ( 0 );
}