About static member variables in C + +

Here are 1 examples to explain:

1#include <iostream>2#include <string>3 using namespacestd;4 5 6 classStudent7 {8     Private://declare a variable as private9     intnum;Ten     stringname; One     intMath; A     int中文版; -     intTotal ; -     Static stringteacher; the     voidcacu_total (); -      -      Public: -     voidInput_stu (); +     voidOutput_stu (); - }; +  AString student::teacher = "Xiaoming"; at intMainintARGC,Char*argv[]) - { - student STU1,STU2; -Student *Pstu; -Pstu =Newstudent; - Stu1.input_stu (); in Stu2.input_stu (); -Pstu->Input_stu (); to      + Stu1.output_stu (); - Stu2.output_stu (); thePstu->Output_stu (); *     DeletePstu; $     return 0;Panax Notoginseng}

For the above code explanation: defines a variable of 2 classes STU1 STU2 how for their member variable

For example, STU1 's num name math and other variables such as STU2 's num name math are different variables

For teacher This member variable, STU1 and STU2 are the same, that is, changing the teacher value in STU1 stu2 the value of teacher will also change

Because they are occupying the same piece of memory.

It is possible to understand that a static member variable is equivalent to defining a global variable in a class that is not stored in the data of each object and that the entire class has only 1 copies

It is also important to note that static member variables, in addition to being declared in a class, must be explicitly defined externally

This is the sentence above:

String student::teacher = "Xiaoming";

About static member variables in C + +