Dealing with functions and reading char

Hi , i am required to use stupid visual c++. somehow there is a bug with reading strings, and im am not allowed to fix it.

so i have to use char instead . .

this is part of of the codes:

Code:

//function prototypes
char read_course_name(char* course_name);

void main(void)
{
	
    char course_name[80];
    read_course_name(course_name);
}

char read_course_name(char* course_name)
{
	
	
	cout<< setw(50);
	cout<<"Course and Subject Entry"; 
	cout<< endl;
	cout<< endl;
	cout<<"\tCourse ==> ";
	

	cin.getline(course_name, 80);

	return course_name;
}

im getting two errors:
error C2440: 'return' : cannot convert from 'char *' to 'char'
error C2664: 'read_course_name' : cannot convert parameter 1 from 'char [80]' to 'char &'

how do i write a function to read an array of characters? the funny thing is ,it ran perfectly using g++ , argghhh

The function read_course_name returns a character pointer.

char *read_course_name(char* course_name);

Monster: thanking you for that but i get a memory error when i try to pass the course name somewhere else . .

it says something with hex-number and memory could not be written on the alert box

Hermit, are you a professional programmer?

Originally posted by hermit
Monster: thanking you for that but i get a memory error when i try to pass the course name somewhere else . .

it says something with hex-number and memory could not be written on the alert box

You are probably writing data to memory that is not allocated.
Post the code where you get the memory error...

B.t.w. void main is wrong, use int main

Code:

#include <iostream.h>
#include <iomanip.h>
#include <string>

// function prototypes
void SortByGPAs( 			// Sort arrays by GPAs
	int NextIndex,       // IN: First unused position in arrays
	int StudIds[],			// IN/OUT: array of student nos - to be sorted
	int SumOfGrades[],	// IN/OUT: array of sums of grades - to be sorted
	int NumSubjs[]);

void Swap(					// Swap the two values
	int &Candidate1,
	int &Candidate2);

void SimpleMindedClrScr(void);// Clear the screen

bool MoreSubjects(void);		// Prompt user for more subjects Y/N?

// routines from Study Guide
void ReadInteger(int &Integer);	// function definition
void Clear(void);			
void ReadChar(char &Char); 	

//my prototypes
char *read_course_name(char* course_name);
void print_welcome(void);
void read_subjects(char* course_name);
void read_subject(char* course_name);
void print_grade_distribution(
	char* course_name,
	char* subject_name, 
	int A, 
	int B, 
	int C, 
	int D);
void check_student_id();

const int MIN_STUDENT_ID = 1000;
const int MAX_STUDENT_ID = 9999;
const int SUBJ_LEN = 7;

int StudIds[MAX_STUDENT_ID - MIN_STUDENT_ID];
int NumSubjs[MAX_STUDENT_ID - MIN_STUDENT_ID];
int SumOfGrades[MAX_STUDENT_ID - MIN_STUDENT_ID];
int next_free = 0;

//function implementations

void main(void)
{
	
    char course_name[80];


	print_welcome();
	read_course_name(course_name);
	read_subjects(course_name);
	
	
	//print_order_of_merit(course_name);
}

void print_welcome(void)
{
	SimpleMindedClrScr();

	cout<<setw(50);
	cout<<"Course Profiling System\n"; 
	cout<<endl;
	cout<<endl;
	cout<<"\t Generates a grade distribution and GPA for each subject and";
	cout<<endl;
	cout<<"\tstudent GPAs with recommendations for commendations & exclusion.\n";
	cout<<endl;
	cout<<endl;
}

char *read_course_name(char* course_name)
{
	

	cout<< setw(50);
	cout<<"Course and Subject Entry"; 
	cout<< endl;
	cout<< endl;
	cout<<"\tCourse ==> ";
	

	cin.getline(course_name, 80);

	return course_name;
}

void read_subjects(char* course_name)
{
	do
	{
		read_subject(course_name);
	} while (MoreSubjects());

}

void read_subject(char* course_name)
{
	char* subject_name;
	int no_of_A = 0;
	int no_of_B = 0;
	int no_of_C = 0;
	int no_of_D = 0;


	cout<<endl;
	cout<< "\tSubject ==>";
	cin >> setw(SUBJ_LEN) >> subject_name;

	SimpleMindedClrScr();
	cout<<"\t\t";
	cout<<course_name;
	cout<<"\t";
	cout<<subject_name;
	cout<<endl;
	cout<<endl;
	cout<<setw(40);
	cout<<"Student Grade Entry" << endl;
	cout<< endl;		
   
	while (1)
	{
		int student_id;
		char grade;
		
		cout<<"\t Student Number (0 to exit) ==> ";
		Clear();
		check_student_id();
		ReadInteger(student_id);

		// Break out of the loop when a 0 student id is entered
		if (student_id == 0)
			break;
		
		cout<<endl;
		cout<<"\t Grade (A,B,C or D) ==> ";
		ReadChar(grade);

		// Search for student id in array
		int i;
		bool found = false;
		for (i=0; i < next_free && !found; i++)
		{
			if (StudIds[i] == student_id)
				found = true;
		}

		if (found)
		{
			// This student id has been used before
			NumSubjs[i]++;
			SumOfGrades[i] +=
				static_cast<int>('C') - static_cast<int>(grade) + 1;
		}
		else
		{
			// This student id is new
			StudIds[next_free] = student_id;
			NumSubjs[next_free] = 1;
			SumOfGrades[next_free] =
				static_cast<int>('C') - static_cast<int>(grade) + 1;
		}

		// Increment the count of different grades
		switch (grade)
		{
		case 'A': no_of_A++; break;
		case 'B': no_of_B++; break;
		case 'C': no_of_C++; break;
		case 'D': no_of_D++; break;
		}

	} // Loop and read another student_id/grade

	print_grade_distribution(course_name, subject_name, no_of_A, no_of_B, no_of_C, no_of_D);
}

void check_student_id()
{

	while(StudIds==false)
	{

		cout<<"ERROR:Must in range 1000....9999 (0 to exit)";
		cout<<endl;
		cout<<endl;
		cout<<"\t Student Number (0 to exit) ==> ";

	}
}

void print_grade_distribution(
	char* course_name, char* subject_name, int A, int B, int C, int D)
{
	int total = A + B + C + D;
	int gpa = ((3 * A) + (2 * B) + (1 * C) + (0 * D)) / total;

	cout << course_name << " " << subject_name << endl;
	cout << endl;
	cout << "Grade Distribution" << endl;
	cout << endl;
	cout << "A  B  C  D   Total" << endl;
	cout << A << " " << B << " " << C << " " << D << " ";

	cout << A + B + C + D << endl;
	cout << endl;

	cout << "Subject GPA: " << gpa << endl;
	cout << endl;
}




/****************************************************************************
 SortByGPAs
 Process:				Sort arrays in descending order by GPA - insertion sort
 							When GPAs are equal, sort in descending order of NumSubjs 
 input:  				int NextIndex: First unused position in arrays
 						   int StudIds[]: array of student nos - to be sorted
 						   int SumOfGrades[]: array of sums of grades - to be sorted 
 						   int NumSubjs[]: array of number of subjects - to be sorted
 output:  				int StudIds[]: array of student nos - sorted
 						   int SumOfGrades[]: array of sums of grades - sorted 
 						   int NumSubjs[]: array of number of subjects - sorted	 
 ****************************************************************************/
void SortByGPAs( 			// Sort arrays by GPAs
	int NextIndex,       // IN: First unused position in arrays
	int StudIds[],			// IN/OUT: array of student nos - to be sorted
	int SumOfGrades[],	// IN/OUT: array of sums of grades - to be sorted
	int NumSubjs[])
{  
	int
		GPABy100,         // GPA multiplied by 100 as an int
		GPABy100Prev;     //     "         "
	
	// NextIndex is first unused position in arrays
	for (int i = 1; i < NextIndex; i++)
	{  
		// Sort into descending GPA order - when GPAs are equal sort 
		// into descending number-of-subjects order
		// To avoid floating-point comparisons, multiply GPAs by 100 and
		// do integer comparisons
	 	for (int j = i; j > 0 && 
	 	  (GPABy100 = SumOfGrades[j] * 100 / NumSubjs[j]) >= 
	 	  (GPABy100Prev = SumOfGrades[j-1] * 100 / NumSubjs[j-1]); j--)
	 	{  
	 		// Swap elements if:  1) GPABy100 is greater
	 		//							 2) GPABy100s are equal and NumSubjs greater
	 		if (GPABy100 > GPABy100Prev || (GPABy100 == GPABy100Prev && 
	 									 NumSubjs[j] > NumSubjs[j-1]))
	 		{  // swap elements in all arrays
		 		Swap(StudIds[j], StudIds[j-1]);    
		 		Swap(NumSubjs[j], NumSubjs[j-1]); 	
		 		Swap(SumOfGrades[j], SumOfGrades[j-1]);			   
		 	}
	 	}
	}	
}

/****************************************************************************
 Swap
 Process:				Swap 2 integer values
 input:  				int &Candidate1: value to be swapped
							int &Candidate2: value to be swapped
 output:  				int &Candidate1: value swapped - old Candidate2
							int &Candidate2: value swapped - old Candidate1	 
 ****************************************************************************/
void Swap(
	int &Candidate1,
	int &Candidate2)
{
 	int TmpSwap;
 	
 	TmpSwap = Candidate1;
 	Candidate1 = Candidate2;
 	Candidate2 = TmpSwap;
}

/****************************************************************************
 MoreSubjects
 Process:				Determine if the user wants to continue. Validate
 							respones (Y/y/N/n valid)
 on entry:				
 on exit:										 							
 input:  							
 output: 				bool function return value: true to continue, false to exit
 ****************************************************************************/
bool MoreSubjects(void)
{  
	char 
		More = ' ';
		
	// loop until user enters Y/y or N/n, printing 
	// error msgs for invalid responses
   while (More != 'Y' && More != 'N') {
	   cout << "Another Subject? "; 
		ReadChar(More);
	   cout << endl;   
		More = toupper(More);       // change to upper case
	   cout << endl; 
	     
	   // output error message if response invalid
	   if (More != 'Y' && More != 'N')
	   	cout << "ERROR: Valid responses are 'Y' or 'N'" << endl << endl;
	} // end while
 	
 	// return user response
	return (More == 'Y');
}  

/****************************************************************************
 SimpleMindedClrScr
 Process:				Clear the screen.
 input:  					 								
 output: 					
 ****************************************************************************/
void SimpleMindedClrScr(void)
{
	const int
		SCREEN_LINES = 24;	
	 
 	for (int i = 0; i < SCREEN_LINES; i++)
 		cout << endl;
}
 
/****************************************************************************
 Clear
 process:				Clear standard input to end of line
 input:  					 								
 output: 			
 ****************************************************************************/
void Clear(void)			
{
	char Char = ' ';
	while (Char != '\n')
	{
		cin.get(Char);
	}
}
 
/****************************************************************************
 ReadChar
 process:				Read a character value from standard input
 input:  					 								
 output: 				int Integer: the value read
 ****************************************************************************/
void ReadChar(char &Char) 	
{
	cin >> Char;
	Clear(); 					// clear to end of line
}

/****************************************************************************
 ReadInteger
 process:				Read (and validate) an integer value from standard input
 input:  					 								
 output: 				int Integer: the value read
 ****************************************************************************/
void ReadInteger(int &Integer)	// function definition
{
	cin >> Integer;
	while (cin.fail())
	{
		cin.clear(); 					// clear input stream flags
		Clear();							// clear to end of line
		cout << "ERROR: You must enter an integer ==> ";
		cin >> Integer;				// try again
	}
	Clear(); 							// clear to end of line
}

Facemaster: nah, im just a beginner . .

dont worry about the #include <string>

it is an error from the microsoft C++ student edition

In your function read_subject you are trying to store the subject name in the variable subject_name.
But the subject_name var is a char pointer an there is no memory allocated to store the value.
Chage it to: char subject_name[80];

Also check the total var in your function print_grade_distribution.
You can get a 'divide by zero' error when total is zero.

can u please explain further on the print_grade function?

Okay, when I run your program and stop at the Student number prompt (enter 0), the print_grade_distribution is called.
Because no grade is filled in the next formula will generate an 'Integer divide by zero' error (because total is zero):

Code:

int gpa = ((3 * A) + (2 * B) + (1 * C) + (0 * D)) / total;

so what do i do ?

Only perform the formula when total is not zero.

Code:

  int gpa = 0;
	
  if(total)
    gpa = ((3 * A) + (2 * B) + (1 * C) + (0 * D)) / total;