struct studInfo
{
char Name[31];
short Idnum;
int Tests;
float avg;
char grade;
};

int main()
{
....
return 0;
}

Originally Posted by jbrock31

Hi everyone. I decided to try and learn C++ on my own and i have ran into a problem and i just need slight kick in the butt.

I am just learning structures and i am practicing using some of the examples at the end of the chapter in my book. When i run the code below i get an error while running the program. The error is a windows error and says my program has encountered a problem and needs to terminate. I know the problem is with *student->Tests, but i am not sure what i am doing wrong.

Any help is greatly appreciated!

#include <iostream>
using namespace std;

struct studInfo
{
char Name[31];
short Idnum;
int* Tests;
float avg;
char grade;
};

void main()
{
short numTests, numStudents;
studInfo* student;
int* testScores;

cout << "How many Students? : ";
cin >> numStudents;
cout << "\nHow many test scores? : ";
cin >> numTests;

student = new studInfo[numStudents];
testScores = new int[numTests];

for ( int i = 0; i < numStudents; i++ )
{
cout << "\nEnter ID for student " << (i + 1) << ": ";
cin >> student->Idnum;
for ( int j = 0; j < numTests; j++ )
{
cout << "\nEnter test score " << (j + 1) << " for student " << i + 1 << ": ";
cin >> *student->Tests;

}
}
}

Originally Posted by kux

you did not allocate memory for the int* Tests variable.

the thing is I have a

testScores = new int[numTests];

but you don't use that nowhere

Now, the thing is like this
Reading your program what you actually try to do is iterate through each student and give to him numTests marks. That means the purpose of int* Tests is to point at the start of an array of numTests elements. That means at each iteration of the outer for you need to allocate memory numTests ints in you int* Tests pointer.

Your program should look like this in oder to just work:

struct studInfo
{
char Name[31];
short Idnum;
int* Tests;
float avg;
char grade;
};

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C++ Syntax (Toggle Plain Text)

void main()
{
	short numTests, numStudents;
	studInfo* student;
	int* testScores;
 
	cout << "How many Students? : ";
	cin >> numStudents;
	cout << "\nHow many test scores? : ";
	cin >> numTests;
 
	student = new studInfo[numStudents];
 
	for ( int i = 0; i < numStudents; i++ )
	{
		cout << "\nEnter ID for student " << (i + 1) << ": ";
		cin >> student[i].Idnum;
 
		testScores = new int[numTests];
 
		for ( int j = 0; j < numTests; j++ )
		{
			cout << "\nEnter test score " << (j + 1) << " for student " << i + 1 << ": ";
			//put the result at tre corresponding position in the array
			cin >> *(testScores + j); //or //cin >> testScores[j]
 
		}
 
		student[i].Tests = testScores;
	}
}

void main() { short numTests, numStudents; studInfo* student; int* testScores; cout << "How many Students? : "; cin >> numStudents; cout << "\nHow many test scores? : "; cin >> numTests; student = new studInfo[numStudents]; for ( int i = 0; i < numStudents; i++ ) { cout << "\nEnter ID for student " << (i + 1) << ": "; cin >> student[i].Idnum; testScores = new int[numTests]; for ( int j = 0; j < numTests; j++ ) { cout << "\nEnter test score " << (j + 1) << " for student " << i + 1 << ": "; //put the result at tre corresponding position in the array cin >> *(testScores + j); //or //cin >> testScores[j] } student[i].Tests = testScores; } }

of course, more problems arrise.
First of all no delete[] are done so you have mem leaks.
Your structure holds a pointer to an array of numTests ints and numTests is a local variable of main. What happens if numTests gets out of scope and you still have allocated studInfo structures? I mean, if you have to iterate through the int* Tests array, how will you know how big it is? Good practice when you hold dinamic arrays in a structure would be to have an int value for each dinamyc array that holds the arrays current size !!

Originally Posted by skatamatic

I would avoid using *(testScores + j) to reference a testScores array location. Use an index instead (testScore[i]). Avoid dereferencing when possible, as horrible messes can arrise from it, when simple indexes could clean up the solution entirely.

Originally Posted by kux

well, i wrote the index version too. but the thing is they both mean the same thing... using an index won't protect you from going beyond the array's size...