typedef defines the structure array type

PS: Typedef defines only an alias (or label) of type XX, which cannot be used directly as a variable, but can only be used to define a variable.
Example 1:

typedef struct st{char id;int num;char name[10];}DATA[10];//The DATA here is not an array, it only means an array type, which cannot be used in the programUse DATA[i] directlyDATA tmp;//It is equivalent to defining an array tmp[10], element type = structure st, which can be used directly in the programtmp[i]

Example 2:

typedef struct {word Head;word Length;byte PDUType;byte SRC_ID[10];byte DST_ID[10];byte PDUdata[200];}TReqFunReg, * PReqFunReg;Typedef TreqFunReg reg[100];//Note: The reg here only represents an array type, not an array. You cannot use reg[i] directly in the program. The correct usage is to use regDefine a variable, this variable is an array with 100 elements, and the element type is the structure TreqFunReg.TreqFunReg reg1[100];//This is the definition of a structure array (without Typedef modification), you can use reg1[i] directly in the programreg aaa; //equivalent to TreqFunReg aaa[100]; aaa[i] can be used directly in the program