This lab will introduce us to separate files and the make command.  These are vital for quick and efficient C++ programming.

Most C++ programs are modularized. If a procedural programming approach is used, the program may be formed of multiple functions and a driver. When an object-oriented programming approach is used, a program may contain multiple classes.  To handle this, multiple files are used for organization.

Header Files:

Contain the declarations for the function names (in procedural programming) and classes (in object oriented programming).  These have a .h or .hpp extension. Often times for functions you will have

return_type function_name(type, type, ...);  // semicolon very important here

/* average.hpp - header file for average function declaration */

double average(int, double); OR

double average(int num_scores, double sum);  // the variables local to the function are optional

Source Files:

Contain the actual definitions of the functions and classes. Generally these have a .cpp file extension or .cc.

/* average.cpp - average function definition */

//Need to use an include of the declarations, use quotes since YOU made the file *not a system file*
// Don't use cin or cout, so no iostream include necessary.  If you don't use it in this file, DON'T INCLUDE IT!!

#include "average.hpp" 

double average(int num_scores, double sum)  // NO SEMICOLON HERE!
{	/* computes the average using an already computed sum and num_scores */
	return sum / num_scores;
}	 

Driver / Main:

Contains the main function and is used to "drive" or test the other functions and classes declared and defined in other files.

/* avg_main.cpp - used to test the average function use */ 

#include <iostream> //necessary for cin/cout
#include "average.hpp" // use the .hpp for includes

using namespace std;

int main(void) 
{ /* Call and test all of the functions written */

	cout << "Welcome to the average driver program.\n";
	cout << "Please enter the number of items to be summed: ";

	int n, count=0;
  double single_score, sum=0;	
	cin >> n;

	while (count < n)  // read in the test scores and sum them
	{
		cout << "Test score " << count + 1 << ":"; 
		cin >> single_score;
		sum += single_score;
		count++; 
	}

 	// Call the average function 
	double avg = average(n, sum);
	cout << "The average of " << sum << "/" << n << " is: " << avg << endl; 
	return 0;
}

Exercise 7.1

Log on to loki.cs.kent.edu using ssh and your llname account.  Change directories (cd) to your  cs23021 folder.  Create a directory named LnameLab7 by using mkdir LnameLab7.

Create the three files as listed above for the average function (average.hpp, average.cpp, avg_main.cpp).

Compile these files using the following commands.

g++ -Wall -c avgerage.cpp

g++ -Wall -c avg_main.cpp

g++ -Wall average.o avg_main.o -o avg

To run the program, type in ./avg

Exercise 7.2

Once you have the files working from the above Exercise, create a new function declaration called sum in the average.hpp.  It should take in one integer parameter that is the number of scores to be summed.  The function should return a double.

Create a new function definition for sum that in the file average.cpp.  sum should take the integer value that is passed to it, and in a loop read in and sum that many double values.  The sum of these values should be returned.  Hint: use the code from Exercise 7.1 as a guide.  Be sure to include any files you may need as well as to use the namespace std.

To compile the average.cpp file and check for errors, use the command:

g++ -Wall -c avgerage.cpp

This does not produce an executable ("runnable") program - it compiles and creates an object .o file, checking for errors.

Copy and use the following driver program to test your newly written function and save it as avg_driver.cpp:

/* avg_driver.cpp - used to test the average functions use */ 

#include <iostream> //necessary for cin/cout
#include "average.hpp" // use the .hpp for includes

using namespace std;

int main(void) 
{ /* Call and test all of the functions written */

	cout << "Welcome to the average driver program.\n";
	cout << "Please enter the number of items to be summed: ";

	int n;	
	cin >> n;

	// Call the sum function to input and sum n numbers
	// Store the returned value in the variable sigma 
	double sigma = sum(n);  // call to your sum function

 	// Call the average function 
	double avg = average(n, sigma);
	cout << "The average of " << sigma << "/" << n << " is: " << avg << endl; 
	return 0;
}

g++ -Wall -c average.cpp

g++ -Wall -c avg_driver.cpp

g++ -Wall avg_driver.o average.o -o avg

./avg