【学习笔记】【C语言】typedef

1.概念

我们可以使用typedef关键字为各种数据类型定义一个新名字(别名)。

2.作用：给已经存在的类型起一个新的名称

3.使用场合：
1> 基本数据类型
2> 指针
3> 结构体
4> 枚举
5> 指向函数的指针

4.代码

#include <stdio.h>

typedef int MyInt;
typedef MyInt MyInt2;

// 给指针类型char *起一个新的类型名称String
typedef char * String;

/*
struct Student
{
int age;
};
typedef struct Student MyStu;
*/

/*
typedef  struct Student
{
int age;
} MyStu;
*/

typedef struct
{
int age;
} MyStu;

/*
enum Sex {Man, Woman};
typedef enum Sex MySex;
*/

typedef enum {
Man,
Woman
} MySex;

typedef int (*MyPoint)(int, int);

int minus(int a, int b)
{
return a - b;
}

int sum(int a, int b)
{
return a + b;
}
/*
struct Person
{
int age;
};

typedef struct Person * PersonPoint;
*/

typedef struct Person
{
int age;
} * PersonPoint;

int main()
{
// 定义结构体变量
struct Person p = {20};

PersonPoint p2 = &p;

//struct Person *p2 = &p;

//MyPoint p = sum;
//MyPoint p2 = minus;
//int (*p)(int, int) = sum;

//int (*p2)(int, int) = minus;

//p(10, 11);

//MySex s = Man;
//enum Sex s = Man;
//enum Sex s2 = Woman;

// struct Student stu3;
//MyStu stu = {20};
//MyStu stu2= {21};

return 0;
}

void test2()
{
String name = "jack";

printf("%s\n", name);
}

void test()
{
int a;
MyInt i = 10;
MyInt2 c = 20;

MyInt b1, b2;

printf("c is %d\n", c);
}

使用注意

#include <stdio.h>

//#define Integer int

//typedef int Integer;

//typedef unsigned long int MyInt;

#define String2 char *

typedef char * String;

int main()
{
/*
int a,b;
int a;
int b;
*/

//s1、s2是char *指针
String s1, s2;
/*
String s1;
String s2;
*/
s1 = "jack";
s2 = "rose";

// s3才是char *指针，s4只是char
String2 s3, s4;
/*
char *s3, s4;
char *s3;
char s4;
*/
//String2 s3 = "jake";

/*
String s1;
String s2;
*/

//Integer i = 10;

return 0;
}