write demo code to describe this pattern,you can wrap some step that must do,but someone of step is not make sure,that should confirmed by subclass in running time.

/*************************************************************************
    > File Name: template_method.cc
  > Author: perrynzhou
  > Mail: perrynzhou@gmail.com
  > Created Time: Tue 15 Aug 2017 07:11:20 AM EDT
 ************************************************************************/

#include <iostream>
using namespace std;
class IDocument {
public:
    IDocument() { cout << "IDocument" << endl; }
    void run()
    {
        step0();
        step1();
        step2();
        step3();
    }

private:
    virtual void step3() = 0;
    void step0() { cout << "...call step0..." << endl; }
    void step1() { cout << "...call step1..." << endl; }
    void step2() { cout << "...call step2..." << endl; }
};
class MyDocument : public IDocument {
public:
    MyDocument() { cout << "MyDocument" << endl; }
private:
    void step3() { cout << "...call MyDocument.step3..." << endl; }
};
int main(void)
{
    MyDocument md;
    md.run();
    return 0;
}