strange c use for macro very good（c语言）

#include "stdafx.h"
#include "myhead.h"

#define MMI_3D_GAME_SWITCH(_index)                     \
{                                                                \
   case _index:                                                  \
      {                                                          \
   printf("你好 世界!\n");          \
      }                                                          \
      break;                                                     \
}

int main(int argc, char* argv[])
{
int i = 1;
switch (i)
{
   MMI_3D_GAME_SWITCH(1)
}
return 0;
}