C Language Development tutorial _ struct, struct pointer, tyepdef, union, enum, tyepdefenum

C Language Development tutorial _ struct, struct pointer, tyepdef, union, enum, tyepdefenum
1. struct definition and initialization

//: The combination of a series of different types of data // array stores a series of sets of the same data type // struct stores a series of sets of different data types struct Student // memory is not allocated at this time, only a struct variable is declared. The variable name is Student {char name [20]; int age; char gender [10]; int classId ;}; struct Student2 {char name [20]; int age; char gender [10]; int classId;} Zeking; // The second definition method // The third definition method // The number of variables that lock the struct. The memory struct {char name [20]; int age is allocated here; char gender [10]; int classId;} stud3, stu4, stu5; // name of the global anonymous struct in stud3 , Similar to the anonymous internal class in java, In order to lock the number of struct variables struct People {char name [20]; int age ;}lucy = {"Lucy", 90 }; // emphasize: type! = Variable. The struct name represents only the struct type and has no memory space. // The members in the struct can use the int main () {// struct Student stu1 defined in the first way; // memory is allocated at this time, in the stack, local variable // ================================================= ========================================================== struct People people1 = {"Zeking ", 20}; struct People people2; // people2.name = "David"; people2.age = 1; strcpy (people2.name, "lucy"); people1.age = 10; printf ("% s, % d \ n ", people1.name, people1.age); system (" pause "); return 0 ;}

2. struct array struct pointer

Struct lele2 {// char name [20]; char * name; int age;} Lucy2 = {"Lucy", 90}; int main () {// struct array initialize int I; struct People2 stu [3] ={{ "Zeking", 30 },{ "David", 32 },{ "Suci ", 28 }}; struct People2 s [5]; for (I = 0; I <5; I ++) {s [I]. age = 20 + I; // strcpy (s [I]. name, "Lucy"); s [I]. name = "lucy"; // assign a value to strcpy for char name [20] // If s [I] is required. name = "lucy" should change the name type to char * name // if you do not understand it, go to the previous blog} for (I = 0; I <5; I ++) {printf ("s % d: % s, % d \ n", I, s [I]. name, s [I]. age );} // ============================== struct pointer ========== ============================= struct lele2 * p = stu; // assign the first address of the array to p, which is equivalent to p = stu; struct People2 * p2; p2 = (People2 *) malloc (sizeof (struct People2) * 4 ); // defines an array with four People2 variables, and then assigns the address of this array to p2 printf ("% # x \ n", & p2 ); memset (p2, 0, sizeof (struct People2) * 4); // initialization, all for 0 for (I = 0; I <4; I ++) {// (p2 + I)-> age = 20 + I; // p2 + I involves pointer displacement. The displacement is sizeof (struct People2) * I // (p2 + I)-> name = "zeking"; // You can also write p2 [I] below. age = 20 + I; p2 [I]. name = "zeking" ;}for (I = 0; I <4; I ++) {printf ("p2: % d: % s, % d \ n ", i, (p2 + I)-> name, (p2 + I)-> age);} system ("pause"); return 0 ;}

3. Add a function pointer to the struct.

struct Man{    int age;    char *name;    int(*Msg)(char *,int);};int message(char *str, int age){    MessageBox(0, TEXT("hello"), TEXT("Lijian"), 0);    return 0;}int main(){    struct Man man;    man.age = 40;    man.name = "Zeking";    man.Msg = message;    man.Msg(man.name,man.age);    system("pause");    return 0;}

4. Add the struct pointer member variable to the struct.

Struct Node {int data; Node * next;}; // ArrayList
 
  
List; // Node node; // list. add (node); // add a data int enqueNode (Node * head, int data) {Node * node = (Node *) to the end of a single-chain table *) malloc (sizeof (Node); if (node = NULL) {return 0;} node-> data = data; node-> next = NULL; // do not let the head value change Node * p = head; while (p-> next! = NULL) {p = p-> next;} p-> next = node;/* while (head-> next! = NULL) {head ++;} */return 1;} int main () {int num = 10; int I = 0; Node * list; list = (Node *) malloc (sizeof (struct Node); list-> data = 0; list-> next = NULL; for (I = 0; I <num; I ++) {enqueNode (list, I + 1);} while (list-> next! = NULL) {printf ("% d \ n", list-> data); list = list-> next;} system ("pause"); return 0 ;}
 

5. typedef command

// Is the alias // java proxy // no new data type is created, but the alias typedef int _ in is created for the existing type; typedef char * string; typedef int (* PFI) (char *, char *); typedef Tnode * Treeptr; typedef struct Tnode {char * word; int count;/* Tnode * left; Tnode * right; */Treeptr left; treeptr right;} BinaryTreeNode; int fun (char *, char *) {return 0;} int main () {_ in a = 20; printf ("% d \ n ", a); string str; str = "hello world"; PFI fp; fp = fun; char * ch; ch = "hello world"; BinaryTreeNode * node; node = (BinaryTreeNode *) malloc (sizeof (BinaryTreeNode); system ("pause"); return 0 ;}

6. public body, enumeration

// Union // put different data types into the same memory. // The memory size occupied is the maximum memory size occupied by the data type. union MyUnion {int a; char B; float c ;}; int main () {MyUnion unio; unio. a = 10; unio. B = 'a'; unio. c = 1.2f; printf ("a: % # x, B: % # x, c: % # x \ n", & unio. a, & unio. b, & unio. c); // only the recently assigned variables printf ("a: % d, B: % c, c: % f \ n", unio. a, unio. b, unio. c); system ("pause"); return 0;} enum {Monday = 10, Saturday, Sunday ,};