C + + Learning Note--season 1

#include <iostream>  // pretreatment  Note: iostream does not take. hint  main ()    {"  AlohaWorld" << Std::endl;     return 0 ;}

#include <iostream>//pretreatment Note: iostream not with. h/*name Space-namespace*/using namespaceStd//once defined, the following program can be used directlyintMain () {cout<<"Aloha World"<< Endl;//You don't have to write Std::cout Std::endl here .    return 0;}//Summary: Not recommended for this purpose

#include <iostream>//pretreatment Note: iostream not with. h/*name Space-namespace*///using namespace std; //once defined, the following program can be used directlyusingstd::cout;usingStd::endl;intMain () {cout<<"Aloha World"<< Endl;//You don't have to write Std::cout Std::endl here .    return 0;}//Summary: This is not recommended, better than using namespace. It's a good idea to define namespaces individually .

1 Basic explanation : extern can be placed before a variable or function to indicate the definition of a variable or function in another file, prompting the compiler to find its definition in other modules when encountering this variable and function. Also extern can be used for link designation.

C + + Learning Note--season 1