Introduction to programming ape (11) -- structure

1、 Declaration of a structure

1.1 Basic knowledge of structure

distinguish ：
A structure is a collection .
Array eleven sets of sets of the same type .

C Built in types in languages （char short int long float double…) Can only represent a single quantity ,
In life, there are often complex objects that we need to express , Such as ：

people ： name + Telephone + Gender + height
book ： Title + author + pricing + Book number

The description of complex objects will use ： Structure

Structure is something worth collecting , These values become member variables . Each member of a structure can be a variable of a different type .

1.2 Statement of structure

For example, describe a person ：

struct Peo
{
    
	char name[20];// name 
	char tele[12];// Telephone 
	char sex[5];// Gender 
	int high;// height 
};

1.3 Type of structure member

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

1.4 Structure variable definition and initialization

Add ：

Printing method and results ：

2、 Access to structure members

#include <stdio.h>

struct Peo
{
    
	char name[20];
	char tele[12];
	char sex[5];
	int high;
};

struct St
{
    
	struct Peo p;
	int num;
	float b;
};

void print1(struct Peo p)
{
    
	printf("%s %s %s %d\n", p.name, p.tele, p.sex, p.high);// Structure pointer . Member variables 
}

void print2(struct Peo* sp)
{
    
	printf("%s %s %s %d\n", sp->name,sp->tele,sp->sex,sp->high);// Structural variable -> Member variables 
}

int main()
{
    
	struct Peo p1 = {
     " Zhang San ","18888888888"," male ","188" };// Creation of structure variables 
	struct St s = {
     {
    " Li Si ","16666666666"," Woman ","166"},100,3.14f };

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

	print1(p1);// Transmissive structure 
	print2(&p1);// Pass structure address 

	return 0;
}

3、 Structural parameters

• stay print1 Function , Directly transfer the structure to the parameter , A formal parameter is a temporary copy of an argument , therefore print1 Function opens up another block in memory and p1 It's the same size , And put p1 The contents of the pass through , This is a waste of space , Another waste of time .
• stay print2 Function , Just pass the address of the structure , Just need 4/8 Bytes of space to store this address , It saves a lot of space , Time .

summary ：

When a function passes parameters , Functions need to be stacked .
If you pass a structure object , The structure is too large , The system overhead of function stack pressing is relatively large , So it can lead to performance degradation .

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