hi, the following code is c++ and it is running. can anyone explain every steps so that i can understand.

MAIN.CPP 

// MAIN.CPP - Case Study, Student Registration

// Count the number of courses taken by the student, calculate total credits

// author KRI

//

#include

#include

#include "course.h"// Course class declaration

#include "regist.h"// Registration class declaration

using namespace std;

// Main program:

// Open an input file stream, read a Registration object,

// including its list of courses. Redisplay all information,

// and calculate the total credits taken. Write the results

// to a file stream.

int main()

{

ifstream infile( "rinput.txt" );

if( !infile ) return -1;

Registration R;

infile >> R;

ofstream ofile( "routput.txt" );

// Use a debugger and track down the calls made "behind the scene"

ofile << R

<< "Number of courses = " << R.GetCount() << ' '

<< "Total credits= " << R.GetCredits() << ' ';

// Declare and initialize a Course, and modify

// its credits.

Course aCourse( "MTH_3020", 'B', 2 );

aCourse.SetCredits( 8 );

cout << aCourse << endl; // the operator << for Course is called

return 0;

}

 COURSE.H 

// COURSE.H - Course class definition

// author KRI

// modified smr

#ifndef COURSE_H

#define COURSE_H

#include

#include // C string library

using namespace std;

const unsigned CourseNameSize = 10;

class Course {

public:

Course();

Course( const char * nam, char sect, unsigned cred );

// Construct a course from a name, section letter,

// and number of credits.

unsigned GetCredits() const;

// Get the number of credits.

void SetCredits( unsigned cred );

// Set the number of credits.

// These operators have been made friends. They have

// privileged access to class internals.

// Very useful for debugging the class, but not very good for class design.

// We will keep using it for now but you will have a chance in a later lab

// to redesign this class.

friend ostream & operator <<( ostream & os, const Course & C );

friend istream & operator >>( istream & input, Course & C );

private:

char name[CourseNameSize];// course name, C style string. not a C++ string object

char section;// section (letter) can be enrolment mode

intcredits;// number of credits

};

inline unsigned Course::GetCredits() const

{

return credits;

}

inline void Course::SetCredits( unsigned cred )

{

credits = cred;

}

#endif

COURSE.CPP 

// COURSE.CPP - Course class implementation

#include "course.h"

Course::Course()

{

name[0] = '\0'; // it is a char * string, not a C++ string object.

}

Course::Course( const char * nam, char sect,

unsigned cred )

{

strncpy( name, nam, CourseNameSize );

section = sect;

credits = cred;

}

istream & operator >>( istream & input, Course & C )

{

input >> C.name >> C.section >> C.credits;

return input;

}

ostream & operator <<( ostream & os, const Course & C )

{

os << "Course:" << C.name << ' '

<< "Section: " << C.section << ' '

<< "Credits: " << C.credits << ' ';

return os;

}

REGIST.H 

// REGIST.H - Registration class definition

// author KRI

// modified smr

#ifndef REGIST_H

#define REGIST_H

#include

#include "course.h"

using namespace std;

const unsigned MaxCourses = 10;

class Registration {

public:

Registration();

unsigned GetCredits() const;

unsigned GetCount() const;

// These operators have been made friends. They have

// privileged access to class internals.

// Very useful for debugging the class, but not very good for class design.

// We will keep using it for now but you will have a chance in a later lab

// to redesign this class.

friend ostream & operator <<( ostream & os,

const Registration & R);

friend istream & operator >>( istream & input,

Registration & R );

private:

long studentId;// student ID number

unsigned semester;// semester year, number

unsigned count;// number of courses

Course courses[MaxCourses]; // array of courses

};

inline unsigned Registration::GetCount() const

{

return count;

}

#endif

REGIST.CPP 

// REGIST.CPP - Registration class implementation.

#include "regist.h"

Registration::Registration()

{

count = 0;

}

unsigned Registration::GetCredits() const

{

unsigned sum = 0;

for(unsigned i = 0; i < count; i++)

sum += courses[i].GetCredits();

return sum;

}

istream & operator >>( istream & input, Registration & R )

{

input >> R.studentId >> R.semester >> R.count;

for(unsigned i = 0; i < R.count; i++)

input >> R.courses[i];// track down which >> operator is called. Hint: look at what is being input.

return input;

}

ostream & operator <<( ostream & os, const Registration & R )

{

os << "Student ID: " << R.studentId << ' '

<< "Semester:" << R.semester << ' ';

for(unsigned i = 0; i < R.count; i++)

os << R.courses[i] << ' ';

return os;

}