typedef struct A
{
void **date;
}B,*C;
//This defines a structure. The name of this structure is A, and then defines two variables B, *C. The type of these two variables is A.
Equivalent to
typedef struct A
{
void **date;
};
A B,*C;
typedef struct
{
void **date;
}D;
//This defines a structure, which has no Name. Then define a variable, the type of this variable is this structure. Similar to int a; the type of a is int.