1.
/*
typedef:给老的数据类型取别名;可以简写复杂的数据类型;
*/
typedef unsigned int ui;
typedef int *pint;//pint是个类型,int *的新名字;
typedef int (*pfunc)(int ,int );//pfunc是个类型,表示函数指针类型;
int add(int a,int b)
{
return a+b;
}
int main(int argc, const char * argv[])
{
ui a = 10;//用新的数据类型定义一个变量;
printf("a=%u\n",a);
int b=20;
pint p = &b;//p是int *型
printf("*p=%d\n",*p);
// pint q[3];//指针数组;
pfunc pf = add;//pf是个变量
printf("add rst=%d\n",pf(a,b));
return 0;
}2.
/*
结构体:关键字 struct
*/
#include <string.h>
struct student//定义了一种新的数据类型;
{
char name[20];//成员变量;存储空间说明:加入是一个鞋柜,char占20个字节,需要20个空间,int 需要4的字节空间,所以工需要28个空间;
int age;
int height;
};
typedef struct student stu;
typedef struct student//定义了一种新的数据类型;
{
char name[20];//成员变量;
int age;
int height;
}stu;
int main()
{
struct student xiaoming = {"xiaoming",18,188};//struct student是数据类型:xiaoming是变量名;
printf("sizeof(struct student) is %lu\n",sizeof(struct student));
//访问结构体的成员变量
xiaoming.age=30;
//1:改名字
strcpy(xiaoming.name,"wangcai");
//2:升级
strcat(xiaoming.name,"6s");
printf("name:%s,age:%d,height:%d\n",xiaoming.name,xiaoming.age,xiaoming.height);
stu xiaohong = {"xiaohong",18,165};
printf("name:%s,age:%d,height:%d\n",xiaohong.name,xiaohong.age,xiaohong.height);
return 0;
}#include <stdlib.h>
typedef struct student//定义了一种新的数据类型;
{
char name[20];//成员变量;
int age;
int height;
}stu;
int main()
{
stu class[10]={};
stu *pst;//pst就是一个指针,stu是pst指向的数据类型;pst可以指向class里的任何一个元素;
//给数组所在元素赋值
class[0].age = 18;
//name :ios1518+2位学号
//height :180,175~180之间浮动
//age :15~24
for(int i=0;i<10;i++)
{
sprintf(class[i].name,"ios1518%02d",i+1);
class[i].age = 15+i;
class[i].height=random()%10+175;//random()表示是随机数;random()%10表示取0~9之间的任意数字;
}
//遍历学生信息
for(int i=0;i<10;i++)
{
printf("name=%s,age=%d,height=%d\n",class[i].name,class[i].age,class[i].height);
}
//按照身高排序:排序的主体是数组的元素,但key是元素的身高,排序需要将整个构造体全部元素进行排序
for(int i=0;i<10-1;i++)
{
for(int j=0;j<10-i-1;j++)
{
if(class[j].height>class[j+1].height)
{
stu temp = class[j];
class[j] = class[j+1];
class[j+1] = temp;
}
}
}
printf("========================================\n");
//遍历学生信息
for(int i=0;i<10;i++)
{
printf("name=%s,age=%d,height=%d\n",class[i].name,class[i].age,class[i].height);
}
//使用pst指针访问数组,
// pst = &class[0];//指针指向首个元素
pst = class;
printf("sizeof(stu)=%lu,sizeof(class)=%lu\n",sizeof(stu),sizeof(class));
//访问第一个元素
printf("first info ,name:%s,age:%d,height:%d\n",pst->name,pst->age,pst->height);
printf("=========================================\n");
//遍历学生信息
for(int i=0;i<10;i++)
{
printf("name:%s,age:%d,height:%d\n",(pst+i)->name,(pst+i)->age,(pst+i)->height);
}
}
typedef struct student
{
char name[20];
int age;
int height;
union//联合体:二选一的关系
{
int stuid;
char nickname[20];
};
/*
共享同一段内存,按情况去解析;
内存大小按大的计算;//所以此结构体占用的内存是20+4+4+20=48字节;
初始化的时候,按照第一个解析;
*/
}stu1;
int main()
{
stu1 xiaohong = {"xiaohong",20,165,0};//开始的时候只能按照int进行初始化,不能用nickname;
strcpy(xiaohong.nickname, "旺财");
printf("%s\n",xiaohong.nickname);
return 0;
}
3.
/*
枚举:一枚一枚的举出来;把一个变量的合理取值列举出来;
枚举是整形常量,把变量的合理取值列举出来;
列举的常量,默认从0开始,后面一次加1;
*/
typedef enum weekday
{
Monday=1,//可设置,后面按照设置的值一次加1;
Tuesday,
Wednesday,
Thursday,
Firday,
Saturday,
Sunday
}WEEKDAY;
int main()
{
// enum weekday day;
WEEKDAY day;
printf("sizeof(day)=%lu\n",sizeof(day));//sizeof(day)=4,因为其实际保存的都是int类型;
printf("Monday=%d\n",Monday);
printf("Sunday=%d\n",Sunday);
printf("请输入周几\n");
scanf("%d",&day);
switch (day)
{
case Monday:
printf("Monday\n");
break;
case Tuesday:
printf("Tuesday\n");
break;
case Wednesday:
printf("Wednesday\n");
break;
case Thursday:
printf("Thursday\n");
break;
case Firday:
printf("Firday\n");
break;
case Saturday:
printf("Saturday\n");
break;
case Sunday:
printf("Sunday\n");
break;
default:
printf("error\n");
break;
}
return 0;
}版权声明：本文为博主原创文章，未经博主允许不得转载。
原文地址：http://blog.csdn.net/throneman/article/details/48102879
