1：命名空间
2：C与C++字符串的区别和基本操作
3：枚举类型
命名空间
#include <string>    #include <ctype.h>#include <vector>#include <iostream>  #include <fstream>// using declarations states our intent to use these names from the namespace std    using namespace  std;namespace one{    string name = "namesapce one的name";}namespace two{    string name = "namesapce two的name";}string name = "全局的name";int main(){
　　//using one::name;//不行，同一范围内重定义，与下面的name有冲突    cout << one::name << endl;    cout << two::name << endl;        string name = "局部name";    cout << name << endl;    cout << ::name << endl; //全局没有范围。没有放在名字空间中的东西都成为放在匿名名字空间，    //匿名就是没有名字，直接用双冒号表示，表示全局的或者外面的    /*    system("pause");*/    return 0;}

#include <string>    #include <ctype.h>#include <vector>#include <iostream>  #include <fstream>// using declarations states our intent to use these names from the namespace std    using namespace  std;void printString(char *s1, char *s2);int main(){    char cs1[30] = "i am cool"; //最多存29个字符，最后一个必须为结尾符,如果定义为csa[9]会出错，没把结尾符算进去    char cs2[30] = "you are cool";        printString(cs1, cs2);    strcpy(cs2, cs1);    printString(cs1, cs2);    cout << "cs1与cs2比较后的结果，返回值为0，-1,1"<<strcmp(cs1, cs2)<< endl;    cout << "cs2的长度为(不包括结尾符) "<<strlen(cs2) << endl;    cout << "将cs1的附加到cs1后面"<<strcat(cs1, cs2) << endl;    cout << cs1 << endl;    return 0;}void printString(char *s1,char *s2){    cout << "s1= "<<s1 << "   s2= "<< s2 << endl;}

#include <string>    #include <ctype.h>#include <vector>#include <iostream>  #include <fstream>// using declarations states our intent to use these names from the namespace std    using namespace  std;void printString(string s1, string s2);int main(){    string cpps1 = "i am cool";    string cpps2 = "you are cool";

　　  string::size_type index= cpps1.find("i");//查找第一个字符出现的位置
　　  cout << index << endl;

　　const char*s1 = cpps1.c_str();// c++风格转换为c风格    printString(cpps1, cpps2);    cpps1 = cpps2;     printString(cpps1, cpps2);/*    cout << "cs1与cs2比较后的结果，返回值为0，-1,1"<<strcmp(cs1, cs2)<< endl;*/    cout << "cs2的长度为(不包括结尾符) "<<cpps2.size() << endl;    cout << "将cs1的附加到cs1后面"<< cpps1+cpps2<< endl;    cout << cpps1 << endl;    cout << "将cs1的附加到cs1后面" << (cpps1+=cpps2) << endl;    cout << cpps1 << endl;    return 0;}void printString(string s1,string s2){    cout << "s1= "<<s1 << "   s2= "<< s2 << endl;}

#include <string>    #include <ctype.h>#include <vector>#include <iostream>  #include <fstream>// using declarations states our intent to use these names from the namespace std    using namespace  std;enum Color{BLACK,WHITE,GREEN,YELLOW,RED};enum Color_me{ BLACK_me, WHITE_me, GREEN_me, YELLOW_me, RED_me };int main(){    int v;    Color c; //c里面的数字虽然看上去像整型，但是是Color型，比整型的范围要小    Color_me c2;    c = BLACK;    cout << c << endl; //输出0    v = c; //将范围小的BLACK复制到Int类型是可行的    cout << v << endl;    //c = v; //将int类型变为BLACK类型不可行，缩小了范围。    //c2 = c; //两个不同的枚举类型之间的值得类型也是不同的，不可以相互赋值    return 0;}