One 、 Declaration of a structure

1. Basic knowledge of structure

A structure is a collection of values , These values are called member variables . Each member of a structure can be a variable of a different type .
A structure is a collection . Each member of the structure can be of different types .

Array Is a collection of elements of the same type , All elements in the array are of the same type .

2. Statement of structure

struct tag//( Structural tag )
{
    
	//（ Member list ）
	//（ Type name   Member variable name ）
	member-list;
}variable-list;//（ Structure variable list ）

for example ：

typedef struct Stu
{
     
	char name[20];// name 
	int age;// Age 
 	char sex[5];// Gender 
	char id[20];// Student number 
}Stu;// You can't lose the semicolon 

struct： Structure keywords , It indicates a structure , The declaration of the structure must have struct.
Structural tag ： It is you who name your structure type
struct  Structural tag ： This represents a structure type
Member list ： You can have multiple members , Each member has its own data type and member variable name .
Structure variable list ： There can be multiple variables , Is a variable created with a structure type , Generally, the list of structural variables is omitted and not written , First declare the structure , Then create structure variables .

3. Type of structure member

The members of a structure can be scalars 、 Array 、 The pointer , Even other structures .

4. Creation and initialization of structure variables

Creation of structure variables ：

Type does not occupy memory , Only after creating variables with types can memory be used .

Initialization of structure variables ：
initialization ： Assign values to variables while creating them

Two 、 Access to structure members

Structural variable  .  Structure member variables
Structure pointer  ->  Structure member variables

1. Structure variables accessing structure members

Structural variables pass through the dot operator （.） Access structure members

2. Structure pointer to access structure members

Structure pointer through operator （->） Access structure members .

3、 ... and 、 Structural parameters

When structures transmit parameters , To transfer the address of the structure .

If the structural variable is passed , A formal parameter is a temporary copy of an argument , It will waste a lot of memory space .

If the address of the structure is passed , The parameter received a pointer , The formal parameter part only needs to open up a memory space of the size of the pointer variable , It only needs 4 Bytes or 8 Bytes , Reduce the waste of space .