[C language] still don't understand the structure? Take a look at this article to give you a preliminary understanding of structure

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List of articles

Preface

Declaration of struct type

Structure initialization

  Structure member access

Structural parameters

  Entrance to exercises

Digression

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Preface

This article explains about C Declaration of structure type in language , Structure initialization , Structure member access , A series of knowledge points that are not easy for novices to master, such as structure transfer parameters

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Tips ： The following is the main body of this article , The following cases can be used for reference

Declaration of struct type

A structure is a combination of values , These values are called member variables , Each member of a structure can be a variable of a different type

Our previous array is a collection of elements of the same type , Structure we have seen char,short,int long,long long And so on are called built-in types , Describe a single type of , There are many complex objects in our life , For example, describing a person needs a name , Telephone , Gender , Height, etc , Describing a book requires a title , author , The unit price , wait , The structure is used to describe complex objects

// Declaration of a structure 
struct peo1
{
	char name[20];
	char sex[5];
	int high;
	char tel[12];
};// In general, this 

struct peo2// Structure name 
{
	char name[20];// Structure member list 
	char sex[5];
	int high;
	char tel[12];
}p1,p2;// Two global structure variables 
int main()
{
	struct peo1 p1;// Creation of structure variables 
	return 0;
}

  Created struct peo1 It's the type , It doesn't actually take up space , And created with this type p1 Variables take up space , It is equivalent to that the type is drawing , and p1 It's the house , The drawing does not occupy an area , Building a house will take up space

The members of a structure can be scalars , Array , The pointer , You can even include a structure in the structure , Note that the contained structure must exist , Otherwise it won't work

Structure initialization

Initializing a structure means that a value is given to the structure when it is created

struct peo
{
	char name[20];
	char sex[5];
	int high;
	char tel[12];
};
struct st
{
	struct peo p;
	int num;
	float f;
};
int main()
{
	struct peo p1 = { "zhangsan"," male ",184,"15545675449" };// Initialization of structure 
	struct st p2 = { {"lisi"," Woman ",167,"15545567544"},122,2.33 };
	printf("%s %s %d %s\n", p1.name, p1.sex, p1.high, p1.tel);
	printf("%s %s %d %s %d %f\n",p2.p.name,p2.p.sex,p2.p.high,p2.p.tel,p2.num,p2.f);
	return 0;
}

  Structure member access

Members of structure variables are accessed through point operators , Accept two operands

Structure pointers access members that point to variables , Sometimes what we need is not a structural variable , It's a pointer to a structure , Such as the function in the following code , An arrow is required to point to the access member

struct peo
{
	char name[20];
	char sex[5];
	int high;
	char tel[12];
};
void print1(struct peo* p1)
{
	printf("%s %s %d %s\n", p1->name, p1->sex, p1->high, p1->tel);// Structure pointer . Member name 
}
void print2(struct peo p1)
{
	printf("%s %s %d %s\n", p1.name, p1.sex, p1.high, p1.tel);// Structural variable . Member name 
}
int main()
{
	struct peo p1 = { "zhangsan"," male ",184,"15545675449" };// Initialization of structure 
	print1(&p1);
	print2(p1);
	return 0;
}

Structural parameters

void print1(struct peo* p1)
{
	printf("%s %s %d %s\n", p1->name, p1->sex, p1->high, p1->tel);// Structure pointer . Member name 
}
void print2(struct peo p1)
{
	printf("%s %s %d %s\n", p1.name, p1.sex, p1.high, p1.tel);// Structural variable . Member name 
}
int main()
{
	struct peo p1 = { "zhangsan"," male ",184,"15545675449" };// Initialization of structure 
	print1(&p1);
	print2(p1);
	return 0;
}

  As a matter of fact, Chuan Shen has already been involved in the above , There are two types of function arguments , The first is to pass the address to , The second is to pass the structure , So which of these two ways is better ？

We learned before , When a function passes parameters , It needs to be pressed , If you pass a structure object , The passed parameter is a temporary copy of the argument , Opening up a space , Cause repetition and waste of space , When passing a past structure object , If the structure is too large , The system overhead of parameter stack pressing is relatively large , It can lead to performance degradation , And if we send the address , The address is 4 A or 8 Bytes , And receiving with a pointer is also 4 perhaps 8 Bytes to receive the address of the first element , We can also find the content of the argument

So when the structure passes parameters , Try to pass the address of the structure

  Entrance to exercises

After reading these specific operations, it is not allowed , You can click on the top to practice some exercises , You can also have a casual look C Some language exercises , Practice multiple-choice questions and programming questions , Let your knowledge be consolidated , Click directly into the title to go directly to , In addition, if you want to get the qualification of internal promotion of large factories, you can also go and have a look ：

Large factory push

Digression

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