C Language Learning Note: 22_ structure

/* * 22. Structure. c * * Created on:2015 July 9 * author:zhong * * #include <stdio.h> #include <stdlib.h>/** * structure : Encapsulation of common data * The structure is a bit of object-oriented thinking, the commonality of a class of things to be closed for use. * * Define struct: *//1> defines struct, can also be defined in function (global and local struct) struct person{char *name;//string int age; double hiegth;}; There is a semicolon at the end of 2>: Defines a struct and creates a struct variable struct person {char *name;//string int age;double hiegth;} p;3>: struct with no name, only once struct { Char *name; string int age;double hiegth;} P * *///---------structure of the basic definition and use-----------------------------------//define the structure, you can also define in the function (global and local structure) struct person {char *name ; string int age;double hiegth;};/ /There is a semicolon ending void use_struct () {//Create constructor variable struct person p = {"Zhong", 18, 159.0};//Create a constructor and assign an initial value (you can use {} assignment only at creation time) P.age = 19;p.hieg th = 170.0; You can use the variable name. The font name of the struct refers to the data segment in the struct body, printf ("%d\n", sizeof (P.name)); 4 Pointers 4 bytes of printf ("%d\n", sizeof (P.age)); 4printf ("%d\n", sizeof (p.hiegth)); 8printf ("%d\n", sizeof (p));   Total size of the structure: 16 The sum of the fields (calculated and if only a large number of 4+4+8, not enough:)//such as: the structure of the most int age, Char C, the current field, their total bytes should be 4+1=5. Because it's not 4.The number of accompany, so fill enough 8, the size of the output structure of 8printf ("P p.age=%d,p.name=%s,p.hiegth=%f\n", P.age, P.name, p.hiegth);} Nested definition of----------struct------------------------/** * struct is a nested definition of a struct that contains another structure: * For example: use struct date to encapsulate date data * Use Person_ to encapsulate a People's information, people's information has a birthday, birthday is a date, you can use the structure of the definition of date to define *///using struct date to encapsulate the data struct date{int year;//int month;//month int day;//Date};// Use Person_ to encapsulate a person's information struct Person_{char *name;//name struct Date birthday;};/ /test void N_struct () {//define a variable for struct person_, and initialize the struct person_ p={"Zhong", {2015,7,9}};//Access data printf for struct body in struct (" P.birthday.year=%d\n ", P.birthday.year);p. birthday.year=2016; Modify the data printf ("p.birthday.year=%d\n", P.birthday.year);} ------struct array-----------------------------void Struct_array () {//defines a struct array and defines a normal array, which is the type name variable name [size] struct person persons[10]={//defines the struct array and assigns the value {"Zhong1", 18,174.0},{"Zhong2", 19,175.0},{"Zhong3", 20,176.0}};//reads a struct and copies it to the variable p, Modify the data in P, the array is not affected by the struct person p=persons[0];p. age=20;//modify the data in P, array is not affected int age=p.age;//read Data printf ("P p.age=%d, P.name=%s,p.hiegth=%f\n ", P.age, P.name, p.hiegth);//The data in the array is modified directly by referencing the field with the array subscript, so the persons[0].age=20;//int age=persons[0].age;//traversal output int i;for (i=0;i<3;i++) {struct Person P=persons[i];p rintf ("P p.age=%d,p.name=%s,p.hiegth=%f\n", P.age, P.name, p.hiegth);}} -------pointer to struct-----------------------void p_struct () {//defines a struct struct student{int id;int age;};/ /define a struct variable holds struct struct Student s={01,19};//defines a struct pointer (the struct Student as a whole, a type), and points to the struct variable sstruct Student *p=&s;/  /Use pointer to modify data, the following two ways can (*p). id=2; p->id=3;//uses pointers to access the structure printf ("s.id=%d,s.age=%d\n", (*p). ID, (*p). age);//can also be written this way printf ("s.id=%d,s.age=%d\n", p- >id,p->age);//p in front without adding *, when writing code with Eclipse, as long as P.age, will automatically become p->age//of course can also be written like this printf ("s.id=%d,s.age=%d\n", S.id, S.age);//p the front without adding *, when writing code with Eclipse, as long as p.age, it will automatically become P->age}int main () {//use_struct ();//struct_array ();//p_struct (); N_struct ();//int a=1;//int *p=&a;//printf ("%p\n", &a);//28ff44//printf ("%p\n", p);//28ff44return 0;}

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C Language Learning Note: 22_ structure