Error if reading char or float

[sh4k3]

i made a simple program to take in two integers and evaluate their sum, product, etc... The problem is, Im wanting to display an error message if the user enters a character or a decimal number, but I have been unsuccessful achieving this. Please help!


here is my program:

#include <stdio.h>

int main(void)
	{	
		int num1=0, num2=0;
		

		int sum, diff1, diff2, product, quotient, average;

		printf("Please enter the first integer:\n");
		scanf("%d",&num1);

		printf("Please enter the second integer:\n");
		scanf("%d",&num2);


		sum = num1 + num2;
		diff1 = num1 - num2;
		diff2 = num2 - num1;
		product = num1*num2;
		quotient = num1/num2;
		average = (num1 + num2)/2;
		
		if(num1 == num2)
			{
				printf("\nCONGRATULATIONS!  The two integers you've entered are equal!\n\n");
			}
		

		printf("The sum of the integers is equal to:%d\n", sum);
		printf("The difference of integer 1 minus integer 2 is equal to:%d\n",diff1);
		printf("The difference of integer 2 minus integer 1 is equal to:%d\n",diff2);
		printf("The product of the integers is equal to:%d\n",product);
		printf("The quotient of the integers is equal to:%d\n",quotient);
		printf("The average of the integers is equal to:%d\n", average);
		

		return(0);

	}

[MacGyver]

http://faq.cprogramming.com/cgi-bin/...&id=1043284385

Welcome to a well-known question.

Quick summary of options:

1) Check the return value of scanf().
2) Use fgets()/sscanf() to get a number.
3) Use fgets()/strtol() to get a number.
4) Write your own number-getting function.

[ulillillia]

One way is to use a string instead and parse it checking for only the numerical characters. That is, something like this:

if (((string[ArrayIndex] >= '0') && (string[ArrayIndex] <= '9')) || (string[ArrayIndex] == 0)) // 0 to 9 characters or the null character
{
	// it's valid and the next character should be checked, except if the null character is encountered
}

else
{
	// it's not valid and an error should be displayed without continuing any further
}

This is just a rough concept and probably a poor/inefficient method. With the string being valid, use atoi to convert the string into a number.

Edit: a better method was posted while I typed the above

[sh4k3]

thx guys
i modified my program to read the scanf()
and it now works!

thanks for your help!