Catalog

1. Declaration of a structure  

1.1 Basic knowledge of structure  

1.2 Declaration of struct type  

1.3 Type of structure member

1.4 Creation and initialization of structure variables

1.4.1 Creation of structure variables ： 

1.4.2 Initialization of structure variables ：

2. Access to structure members

2.1 Structure variables accessing structure members  

2.2  Structure pointer to access structure members  

2.3  Summary of visits of structure members

3. Structural parameters

1. Declaration of a structure  

1.1 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 in the structure can be of different types .

Analogy and distinction ： An array is a collection of elements of the same type , All elements in the array are of the same type .

At present, we have learned some types : Character (char), integer (short,int...), floating-point (float,double) , These types are built-in types .

But there are always some complex objects in life , such as ： people , People have names , Gender , Telephone , Height, etc ; Another example ： book , Books have titles , author , pricing , Book number, etc , These complex objects cannot be described by built-in types . So how to describe these complex objects ？ So there is the emergence of structure , A structure is a User defined data type , Custom type , Is used to describe complex objects .

1.2 Declaration of struct type  

struct： Structure keywords , It indicates a structure , The declaration of the structure must have struct.

Structural tag ： It is the name you give 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 .

Take an example of a structure type declaration ：

The following is the case with a list of structural variables  

1.3 Type of structure member

  Members of a structure can be scalars （int,float,double）、 Array 、 The pointer , Even other structures ( Variable ).

  such as ：

1.4 Creation and initialization of structure variables

1.4.1 Creation of structure variables ： 

Create local variables p1: 

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

Create global variables p2,p3: 

1.4.2 Initialization of structure variables ：

  initialization ： Assign values to variables while creating them .

2. Access to structure members

Structural variable  . Structure member variables

Structure pointer  -> Structure member variables

2.1 Structure variables accessing structure members  

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

Structural variable  . Structure member variables

like this ： 

give an example 1：

#include <stdio.h>

// The declared structure type is ：struct Peo
struct Peo
{
	char name[20];
	char sex[5];
	char tele[12];
	int high;
};

// The declared structure type is ：struct S
struct S
{
	struct Peo p;
	int sum;
	float f;
};

int main()
{
	struct Peo p1 = { " Zhang San "," male ","12366784567",183 };
	struct S s = { {" Li Si "," male ","12366784567",186},10,3.14f };

	printf("%s %s %s %d\n",p1.name,p1.sex,p1.tele,p1.high);
	printf("%s %s %s %d %d %f",s.p.name,s.p.sex,s.p.tele,s.p.high,s.sum,s.f);

	return 0;
}

  give an example 2： Structural parameters （ The structural variables are passed ）

The code is as follows ： 

#include <stdio.h>

// The declared structure type is ：struct Peo
struct Peo
{
	char name[20];
	char sex[5];
	char tele[12];
	int high;
};

void print(struct Peo sp)// Structure type variables to receive 
{
	printf("%s %s %s %d\n", sp.name, sp.sex, sp.tele, sp.high);

}

int main()
{
	struct Peo p1 = { " Zhang San "," male ","12366784567",183 };
	print(p1);// It is a variable of structure type 
	return 0;
}

2.2  Structure pointer to access structure members  

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

Structure pointer  -> Structure member variables

like this ：

  give an example ： Structural parameters （ The address of the structure variable is passed ）

#include <stdio.h>

// The declared structure type is ：struct Peo
struct Peo
{
	char name[20];
	char sex[5];
	char tele[12];
	int high;
};


void print(struct Peo* sp)// Structure type pointer to receive 
{
	printf("%s %s %s %d\n", sp->name, sp->sex, sp->tele, sp->high);
	
}

int main()
{
	struct Peo p1 = { " Zhang San "," male ","12366784567",183 };
	print(&p1);// The address of the variable name of the structure is passed , Address of structure type 

	return 0;
}

2.3  Summary of visits of structure members

Structural variable  . Structure member variables

Structure pointer  -> Structure member variables

give an example ： 

The code is as follows ： 

#include <stdio.h>

// The declared structure type is ：struct Peo
struct Peo
{
	char name[20];
	char sex[5];
	char tele[12];
	int high;
};

// The declared structure type is ：struct S
struct S
{
	struct Peo p;
	int sum;
	float f;
};

void print(struct Peo* sp,struct S* ss)// Structure type pointer to receive 
{
	printf("%s %s %s %d\n",sp->name,sp->sex,sp->tele,sp->high);
	// Structure pointer -> Structure member variables ：sp->name
	printf("%s %s %s %d %d %f\n",ss->p.name,ss->p.sex,ss->p.tele,ss->p.high,ss->sum,ss->f);
	// Structure pointer -> Structure member variables ：ss->p   Structural variable . Structure member variables ：p.name
}

int main()
{
	struct Peo p1 = { " Zhang San "," male ","12366784567",183 };
	struct S s = { {" Li Si "," male ","12366784567",186},10,3.14f };

	print(&p1,&s);// The address of the variable name of the structure is passed , Address of structure type 

	return 0;
}

3. 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 .