Programming Forums > Application Development > C++

b1g4L · Feb 2nd, 2006, 7:08 PM

Here is a simple program that models a student. It can hold a student name, ID #, and grade. I believe I have the class setup correctly. I'm having a problem writing a system driver file & header file. Could someone explain to me how two construct each of these?

(Toggle Plain Text)

#include <iostream>
using namespace std;

class Student
{
    private:
    //global variables
    string studentName;
    int studentIdNum;
    double studentGrade;
    
    public:
    Student ()                       //default constructor
    {
        studentName = "";
        studentIdNum = 0;
        studentGrade = 0;
    }
    
    string getName ()                //method returns student name
    {
        return studentName;
    }
    
    int getIdNum ()                  //method returns ID number
    {
        return studentIdNum;
    }
    
    double getGrade ()               //method returns grade
    {
        return studentGrade;
    }
    
    void setName (string name)       //method sets student name
    {
        studentName = name;
    }
    
    void setIdNum (int idNum)        //method sets ID number
    {
        studentIdNum = idNum;
    }
    
    void setGrade (double grade)     //method sets grade
    {
        studentGrade = grade;
    }
};

Seif · Feb 2nd, 2006, 7:22 PM

hi. im not too shit hot on class's but in the public so may be wrong but to construct a student you need to put Student:

tudent() to construct it then say int Student::getIdNum() {method} for all the methods.

however dont take my word for it as my subname would suggest, i am a noob ^^.

Seif · Feb 2nd, 2006, 7:23 PM

actually i think i misread the question lol ignore me sorry. been a long day

.

b1g4L · Feb 2nd, 2006, 7:49 PM

thanks anyway. I'm just looking how to write a driver file and header file for this Student class.....as separate files, but in the same directory. I appreciate any help.

DaWei · Feb 2nd, 2006, 8:25 PM

The term 'driver file' means nothing. Perhaps you mean a file containing the code to use the class. Typically, one would define the class in a header (.h) file and the using code in a source (.cpp) file. The header is included at the top of the source file. This causes it to be copied and pasted (invisibly to you) into the source file at the point of inclusion.

If you don't understand what I'm saying, post back and I'll post an example.

Seif, if you don't know a correct answer, please refrain from giving one. Misleading answers are worse than no answer. With no answer the questioner will continue to seek. With a wrong answer the questioner feels as if he's got what he needs, and produces unworkable pieces of crap. See my lounge post, "Please Be Careful...".

b1g4L · Feb 2nd, 2006, 10:01 PM

I think I was thinking of a test driver. Maybe thats it. What I'm saying is that I don't know how to write a header file. I pulled this example of the Student class because it was easy and I figured someone could should me how to go about writing a header file for the Student class.

Jessehk · Feb 2nd, 2006, 10:17 PM

A header file (usually *.h) contains (in most cases) declarations, not definitions.
In other words, the way to make the class you wrote into a header file would be to declare the class (maybe in a student.h file), then define the methods in a *.cpp file, and then finally write a program that utilizes the class.

for example: (code has been mostly snipped)

student.h

(Toggle Plain Text)

#ifndef STUDENT_H_ 
#define STUDENT_H_
//previous prevents the header file from being
//included more than once

#include <iostream>

class Student
{
	private:
		//etc
	public:
		//etc
};

#endif

student.cpp

(Toggle Plain Text)

#include "student.h"

//define constructor
Student::Student() : studentName(""), studentIdNumber(0), studentGrade(0)
{
}

//define the other methods

I would also recommend that you don't use namespace std; in a header file.

b1g4L · Feb 2nd, 2006, 10:30 PM

thanks. Now, how would I create a student object from another .cpp file? I tried the following:

(Toggle Plain Text)

#include <iostream>
using namespace std;

int main ()
{
    Student stud = new Student;
    stud.setName("Bob");
    
    return 0;
}

I'm coming from a background in Java, if your were wondering....

grumpy · Feb 2nd, 2006, 10:44 PM

Put the class declaration into a header file (eg student.h). A couple of things to remember;

1) Never have a "using namespace" directive in a header file. Doing so can break code that #include's that header file, and can make you extremely unpopular if other people wish to reuse your code.

2) Unless you have a specific reason to inline your member functions, don't. Or, to put it another way, by default you should remove the bodies of all member functions from within your class declaration.

3) Unless you have a specific reason not to, employ an include guard on the header file. The working of an include guard is a macro with a name that is unique to the header file (no other header files or source files declare it or use it).

An example header file might be;

(Toggle Plain Text)

#ifndef STUDENT_H_INCLUDED     // this is the include guard
#define STUDENT_H_INCLUDED

#include <string>

class Student
{
    private:
    //global variables      //   Your description of these as "global variables" is incorrect
    std::string studentName;
    int studentIdNum;
    double studentGrade;
    
    public:
    Student ();           //default constructor
   
    std::string getName ();   //method returns student name
   
    int getIdNum ();                  //method returns ID number

    double getGrade ();               //method returns grade
    
    void setName (std::string name);       //method sets student name

    void setIdNum (int idNum);        //method sets ID number
    
    void setGrade (double grade);     //method sets grade
};

#endif

Then structure a source file (eg student.cpp) along the following lines

(Toggle Plain Text)

#include <system_headers_needed_for_student_class>

#include "student.h"

#include "other_headers_needed_to_make_student_class_work"

//  instantiate any static members of the class.  Not relevant in your example,
//    as you have no static members.
//    For example, if the Student class has a static member of type
//     X named x that you want initialised using an integer value 0....

X Student::x(0);

//    Provide definitions (the bodies) for all member functions of Student
//     Remove bodies from your class declaration and implement them separately.
//     For example;

Student::Student () : studentName(""),  studentIdNum(0), studentGrade(0)      //default constructor
{
     //   note that, for constructors, it is better to use initialiser lists rather
     //    than assigning members in the constructor body.
     //    Only use the constructor body for doing things other than initialising
     //      members of the class.  
}

If, by "driver file" you mean a little test program to test your student class, create a file named (say) test.cpp containing

(Toggle Plain Text)

#include <system_headers_needed_to_make_test_work>

#include "student.h"

#include "any_other_headers_needed_to_make_test_work"

int main()
{
     // code to test the Student class goes here
     return 0;
}

To build a test program, you will need to compile all of the relevant source files, and link the objects into a working executable. The way you do this depends on your development environment (what compiler, what IDE if any, etc etc).

Unrelated to your question, consider using the const keyword. For example, your member getGrade() does not change any data members of a Student, so within the class declaration, would be better used as;

(Toggle Plain Text)

    double getGrade() const;

Yes, it's obvious you've come from a Java background. Your programming style is showing all sorts of the worst coding practices that, unfortunately, Java tends to encourage.

Feb 2nd, 2006, 7:08 PM	#1
b1g4L Programmer Join Date: Dec 2005 Location: SC Posts: 38 Rep Power: 0	system driver / header file Here is a simple program that models a student. It can hold a student name, ID #, and grade. I believe I have the class setup correctly. I'm having a problem writing a system driver file & header file. Could someone explain to me how two construct each of these? (Toggle Plain Text) #include <iostream> using namespace std; class Student { private: //global variables string studentName; int studentIdNum; double studentGrade; public: Student () //default constructor { studentName = ""; studentIdNum = 0; studentGrade = 0; } string getName () //method returns student name { return studentName; } int getIdNum () //method returns ID number { return studentIdNum; } double getGrade () //method returns grade { return studentGrade; } void setName (string name) //method sets student name { studentName = name; } void setIdNum (int idNum) //method sets ID number { studentIdNum = idNum; } void setGrade (double grade) //method sets grade { studentGrade = grade; } }; #include <iostream> using namespace std; class Student { private: //global variables string studentName; int studentIdNum; double studentGrade; public: Student () //default constructor { studentName = ""; studentIdNum = 0; studentGrade = 0; } string getName () //method returns student name { return studentName; } int getIdNum () //method returns ID number { return studentIdNum; } double getGrade () //method returns grade { return studentGrade; } void setName (string name) //method sets student name { studentName = name; } void setIdNum (int idNum) //method sets ID number { studentIdNum = idNum; } void setGrade (double grade) //method sets grade { studentGrade = grade; } };

Feb 2nd, 2006, 7:22 PM	#2
Seif Hobbyist Programmer Join Date: Jan 2006 Location: UK Posts: 214 Rep Power: 3	hi. im not too shit hot on class's but in the public so may be wrong but to construct a student you need to put Student:tudent() to construct it then say int Student::getIdNum() {method} for all the methods. however dont take my word for it as my subname would suggest, i am a noob ^^.

Feb 2nd, 2006, 8:25 PM	#5
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	The term 'driver file' means nothing. Perhaps you mean a file containing the code to use the class. Typically, one would define the class in a header (.h) file and the using code in a source (.cpp) file. The header is included at the top of the source file. This causes it to be copied and pasted (invisibly to you) into the source file at the point of inclusion. If you don't understand what I'm saying, post back and I'll post an example. Seif, if you don't know a correct answer, please refrain from giving one. Misleading answers are worse than no answer. With no answer the questioner will continue to seek. With a wrong answer the questioner feels as if he's got what he needs, and produces unworkable pieces of crap. See my lounge post, "Please Be Careful...". __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Feb 2nd, 2006, 10:17 PM	#7
Jessehk The Oblivious One Join Date: May 2005 Location: Ontario, Canada Posts: 641 Rep Power: 4	A header file (usually .h) contains (in most cases) declarations, not definitions. In other words, the way to make the class you wrote into a header file would be to declare the class (maybe in a student.h file), then define the methods in a .cpp file, and then finally write a program that utilizes the class. for example: (code has been mostly snipped) student.h (Toggle Plain Text) #ifndef STUDENT_H_ #define STUDENT_H_ //previous prevents the header file from being //included more than once #include <iostream> class Student { private: //etc public: //etc }; #endif #ifndef STUDENT_H_ #define STUDENT_H_ //previous prevents the header file from being //included more than once #include <iostream> class Student { private: //etc public: //etc }; #endif student.cpp (Toggle Plain Text) #include "student.h" //define constructor Student::Student() : studentName(""), studentIdNumber(0), studentGrade(0) { } //define the other methods #include "student.h" //define constructor Student::Student() : studentName(""), studentIdNumber(0), studentGrade(0) { } //define the other methods I would also recommend that you don't use namespace std; in a header file. __________________ Dr. Zoidberg: [ecstatic] I'm going to a movie... with FRIENDS!

Feb 2nd, 2006, 10:30 PM	#8
b1g4L Programmer Join Date: Dec 2005 Location: SC Posts: 38 Rep Power: 0	thanks. Now, how would I create a student object from another .cpp file? I tried the following: (Toggle Plain Text) #include <iostream> using namespace std; int main () { Student stud = new Student; stud.setName("Bob"); return 0; } #include <iostream> using namespace std; int main () { Student stud = new Student; stud.setName("Bob"); return 0; } I'm coming from a background in Java, if your were wondering....

Feb 2nd, 2006, 7:23 PM	#3
Seif Hobbyist Programmer Join Date: Jan 2006 Location: UK Posts: 214 Rep Power: 3	actually i think i misread the question lol ignore me sorry. been a long day .

Feb 2nd, 2006, 7:49 PM	#4
b1g4L Programmer Join Date: Dec 2005 Location: SC Posts: 38 Rep Power: 0	thanks anyway. I'm just looking how to write a driver file and header file for this Student class.....as separate files, but in the same directory. I appreciate any help.

Feb 2nd, 2006, 10:01 PM	#6
b1g4L Programmer Join Date: Dec 2005 Location: SC Posts: 38 Rep Power: 0	I think I was thinking of a test driver. Maybe thats it. What I'm saying is that I don't know how to write a header file. I pulled this example of the Student class because it was easy and I figured someone could should me how to go about writing a header file for the Student class.

Feb 2nd, 2006, 10:44 PM	#9
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,207 Rep Power: 5	Put the class declaration into a header file (eg student.h). A couple of things to remember; 1) Never have a "using namespace" directive in a header file. Doing so can break code that #include's that header file, and can make you extremely unpopular if other people wish to reuse your code. 2) Unless you have a specific reason to inline your member functions, don't. Or, to put it another way, by default you should remove the bodies of all member functions from within your class declaration. 3) Unless you have a specific reason not to, employ an include guard on the header file. The working of an include guard is a macro with a name that is unique to the header file (no other header files or source files declare it or use it). An example header file might be; (Toggle Plain Text) #ifndef STUDENT_H_INCLUDED // this is the include guard #define STUDENT_H_INCLUDED #include <string> class Student { private: //global variables // Your description of these as "global variables" is incorrect std::string studentName; int studentIdNum; double studentGrade; public: Student (); //default constructor std::string getName (); //method returns student name int getIdNum (); //method returns ID number double getGrade (); //method returns grade void setName (std::string name); //method sets student name void setIdNum (int idNum); //method sets ID number void setGrade (double grade); //method sets grade }; #endif #ifndef STUDENT_H_INCLUDED // this is the include guard #define STUDENT_H_INCLUDED #include <string> class Student { private: //global variables // Your description of these as "global variables" is incorrect std::string studentName; int studentIdNum; double studentGrade; public: Student (); //default constructor std::string getName (); //method returns student name int getIdNum (); //method returns ID number double getGrade (); //method returns grade void setName (std::string name); //method sets student name void setIdNum (int idNum); //method sets ID number void setGrade (double grade); //method sets grade }; #endif Then structure a source file (eg student.cpp) along the following lines (Toggle Plain Text) #include <system_headers_needed_for_student_class> #include "student.h" #include "other_headers_needed_to_make_student_class_work" // instantiate any static members of the class. Not relevant in your example, // as you have no static members. // For example, if the Student class has a static member of type // X named x that you want initialised using an integer value 0.... X Student::x(0); // Provide definitions (the bodies) for all member functions of Student // Remove bodies from your class declaration and implement them separately. // For example; Student::Student () : studentName(""), studentIdNum(0), studentGrade(0) //default constructor { // note that, for constructors, it is better to use initialiser lists rather // than assigning members in the constructor body. // Only use the constructor body for doing things other than initialising // members of the class. } #include <system_headers_needed_for_student_class> #include "student.h" #include "other_headers_needed_to_make_student_class_work" // instantiate any static members of the class. Not relevant in your example, // as you have no static members. // For example, if the Student class has a static member of type // X named x that you want initialised using an integer value 0.... X Student::x(0); // Provide definitions (the bodies) for all member functions of Student // Remove bodies from your class declaration and implement them separately. // For example; Student::Student () : studentName(""), studentIdNum(0), studentGrade(0) //default constructor { // note that, for constructors, it is better to use initialiser lists rather // than assigning members in the constructor body. // Only use the constructor body for doing things other than initialising // members of the class. } If, by "driver file" you mean a little test program to test your student class, create a file named (say) test.cpp containing (Toggle Plain Text) #include <system_headers_needed_to_make_test_work> #include "student.h" #include "any_other_headers_needed_to_make_test_work" int main() { // code to test the Student class goes here return 0; } #include <system_headers_needed_to_make_test_work> #include "student.h" #include "any_other_headers_needed_to_make_test_work" int main() { // code to test the Student class goes here return 0; } To build a test program, you will need to compile all of the relevant source files, and link the objects into a working executable. The way you do this depends on your development environment (what compiler, what IDE if any, etc etc). Unrelated to your question, consider using the const keyword. For example, your member getGrade() does not change any data members of a Student, so within the class declaration, would be better used as; (Toggle Plain Text) double getGrade() const; double getGrade() const; Yes, it's obvious you've come from a Java background. Your programming style is showing all sorts of the worst coding practices that, unfortunately, Java tends to encourage.

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Programming Forums > Application Development > C++

system driver / header file