C + + namespaces, differences between C and C + + strings, enumeration types

 1: Name space
The difference between 2:C and C + + string and basic operation
3: Enum type
Name Space 
#include <string>#include<ctype.h>#include<vector>#include<iostream>#include<fstream>//using declarations states our intent to use these names from the namespace Stdusing namespacestd;namespaceone{stringName ="Namesapce one's name";}namespacetwo{stringName ="NAMESAPCE The name of the";}stringName ="the global name";intMain () {
Using one::name;//No, redefine within the same scope, conflict with name below cout<< One::name <<Endl; cout<< Two::name <<Endl; stringName ="Local name"; cout<< name <<Endl; cout<<:: Name << Endl;//The global has no scope. Everything that's not in the namespace is placed in an anonymous namespace,//Anonymous is not a name, directly with a double colon, representing the global or the outside    /*System ("pause");*/    return 0;}

C-style strings and C + + differences

#include <string>#include<ctype.h>#include<vector>#include<iostream>#include<fstream>//using declarations states our intent to use these names from the namespace Stdusing namespacestd;voidPrintstring (Char*S1,Char*S2);intMain () {Charcs1[ -] ="I am cool";//a maximum of 29 characters, the last must be a trailing character, if defined as csa[9] will be an error, do not count the end character in    Charcs2[ -] ="You are cool";    Printstring (CS1, CS2);    strcpy (CS2, CS1);    Printstring (CS1, CS2); cout<<"CS1 compared to CS2, the return value is 0,-1,1"&LT;&LT;STRCMP (CS1, CS2) <<Endl; cout<<"the length of the CS2 is (not including the end character)"<<strlen (CS2) <<Endl; cout<<"attach the CS1 to the CS1 back"<<strcat (CS1, CS2) <<Endl; cout<< CS1 <<Endl; return 0;}voidPrintstring (Char*S1,Char*S2) {cout<<"s1="&LT;&LT;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 Stdusing namespacestd;voidPrintstring (stringS1,stringS2);intMain () {stringCPPS1 ="I am cool"; stringCPPS2 ="You are cool";

String::size_type index= cpps1.find ("i");//Find where the first character appears
cout << index << Endl;

Const CHAR*S1 = CPPS1.C_STR ();//C + + style conversion to C-style printstring (CPPS1, CPPS2); Cpps1=CPPS2; Printstring (CPPS1, CPPS2);/*cout << "CS1 compared to CS2 results, the return value is 0,-1,1" <<strcmp (CS1, CS2) << Endl;*/cout<<"the length of the CS2 is (not including the end character)"<<cpps2.size () <<Endl; cout<<"attach the CS1 to the CS1 back"<< cpps1+cpps2<<Endl; cout<< Cpps1 <<Endl; cout<<"attach the CS1 to the CS1 back"<< (CPPS1+=CPPS2) <<Endl; cout<< Cpps1 <<Endl; return 0;}voidPrintstring (stringS1,stringS2) {cout<<"s1="&LT;&LT;S1 <<"s2="<< S2 <<Endl;}

When two strings are mixed, they automatically turn into C + + style

Enum type

#include <string>#include<ctype.h>#include<vector>#include<iostream>#include<fstream>//using declarations states our intent to use these names from the namespace Stdusing namespacestd;enumcolor{black,white,green,yellow,red};enumcolor_me{Black_me, White_me, Green_me, Yellow_me, red_me};intMain () {intv; Color C; //the number in C looks like an integer, but it's a color type, smaller than the range of integers.Color_me C2; C=BLACK; cout<< c << Endl;//Output 0v = c;//It is possible to copy a small range of black to int typecout << v <<Endl; //C = v;//Changing the int type to black type is not possible, narrowing the range. //C2 = c;//two different enumeration types are also different from each other and cannot be assigned to one another .    return 0;}