Thread: problems with error-handling

My assignment in my extremely basic C++ class is to create a program which tells the user if a is a factor of b, and vice versa.

Well thats fine and dandy, and takes a minute to code, but as a challenge to myself I decided to make the program "smart" - not let the user crash it or enter non-numeric values. Anyways, this is what I have so far, but it just doesn't work:

Code:

// By Will Herrick
// takes two numbers and sees if they are factors of each other.
// also some practice on error-handling.
// last updated 9-26-02 (doesn't work quite yet!)

#include <iostream>
#include <cstdlib>

using namespace std;

int checkSize(int);
int checkNumeric(char[6]);
void factor(int,int);
int getNumber();

int main()
{
	int ai;
	int bi;
	int exit = 0;
	int ans;

	do
	{
		cout << "Enter a:";
		ai = getNumber();
		cout << endl << "Enter b:";
		bi = getNumber();
		cout << endl;
		factor(ai,bi);
		cout << "Try Again(1) or Quit(2)? ";
		cin >> ans;
		if(ans == 1) exit = 0;
		if(ans == 0) exit = 1;
		else 
		{
			cout << endl << "Thats not a possible choice, try again: ";
			cin >> ans;
		}
	} while(exit==0);
	system("PAUSE");
	return 0;
}

int checkSize(int a)
{
	if(a > 32766)
	{
		return 0;
	}
	if(a < 32766) return 1;
}

int checkNumeric(char a[6])
{
	int x;
	int i;
 int marker;
	
	for(x = 0; x < 6; x++)
	{
		i = a[x];
		if((i < 48 || i > 57) && i != '\0')
		{
			marker = 1;
		}
	}
	if(marker == 1) return 0;
 if(marker != 1) return 1;
}

void factor(int a, int b)
{
		if(a % b == 0) cout << b << " is a factor of " << a << endl;
		if(b % a == 0) cout << a << " is a factor of " << b << endl;
		if(a % b != 0 && b % a != 0) cout << "Neither number is a factor of the other." << endl;
}

int getNumber()
{
	char a[6];
	char *p;
	int r;
	int isNum;
	int isSize;
	
	cout << endl << "Enter the NUMBER: ";
	cin.get(a,6);
	cin.ignore(80, '\n');
	isNum = checkNumeric(a);
	if(isNum == 1)
	{
		p = &a[0];
		r = atoi(p);
		isSize = checkSize(r);
		if(isSize == 1) return r;
		else 
		{
			r = getNumber();
			return r;
		}
	}
	if(isNum == 0) 
	{
		r = getNumber();
		return r;
	}
}

The problem is that no matter what the user enters, it thinks its not a number even if it is. [edit - just made one change, fixes one problem, but still doesn't work]

Oh and if their a much easier way of doing this that'd be great too.

Thanks.